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| MANUAL Tsunami Simulation / Visualization Code NAMI DANCE version 4.9 |
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Middle East Technical University |
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1. METHOD IN TSUNAMI
MODELING
State-of-the-art and
Phases of Tsunami
Modeling
Tsunami is one of the most important
marine hazards generally triggered by earthquakes and/or submarine/subaerial
landslides. In general, tsunami might affect not only the area where it is
generated but substantial distance away from generation region. Tsunami science
needs close cooperation between basic and applied sciences and also from
international to local level authorities.
The tsunami modeling and risk analysis are necessary for better
preparedness and proper mitigation measures in the framework of international
collaborations. Better understanding, wider awareness, proper preparedness and
effective mitigation strategies for tsunamis need close international
collaboration from different scientific and engineering disciplines with
exchange and enhancement of existing data, development and utilization of
available computational tools.
Modeling is one of the essential
components of tsunami studies in scientific and operational level. Tsunami
modelling has several phases in which exchange and enhance of available
earthquake and tsunami data, bathymetric and topographic data in sufficient
resolution, selection of possible or credible tsunami scenarios, selection and
application of the validated and verified numerical tools for tsunami
generation, propagation, inundation and visualization must be covered.
In general, there are several unique phases of tsunami modeling for
a specific region. They are summarized in the Appendix A.
2. BRIEF HISTORY AND CAPABILITIES OF NAMI DANCE
Tsunami numerical modeling by NAMI DANCE is based on the solution of nonlinear form
of the long wave equations with respect to related initial and boundary
conditions. There were several numerical solutions of long wave equations for
tsunamis. In general the explicit numerical solution of Nonlinear Shallow Water
(NSW). Equations is preferable for the use since it uses reasonable computer
time and memory, and also provides the results in acceptable error limit. The
most important development in tsunami modeling has been achieved by Profs. Shuto
and Imamura by developing model TUNAMI N2 and opened to the use of tsunami
scientsits under the umbrella of UNESCO (Imamura, 1989, Shuto, Goto, Imamura,
1990, Goto and Ogawa, 1991).
TUNAMI N2
determines the tsunami source characteristics from earthquake rupture
characteristics. It computes all necessary parameters of tsunami behavior in
shallow water and in the inundation zone allowing for a better understanding of
the effect of tsunamis according to bathymetric and topographical conditions.
NAMI DANCE has been developed by Profs. Zaytsev, Chernov, Yalciner, Pelinovsky
and Kurkin using the identical computational procedures of TUNAMI N2. Both codes
are cross tested also verified in international workshops specifically organized
for testing and verifications of tsunami models (Synolakis, Liu, Yeh, 2004,
Yalciner et. al., 2007b). These models have been applied several tsunami
application all over the world (some of references are Yalciner et. al. 1995,
2002 a,b,c 2007 a,b, Zahibo et. al. 2003 a,b)
As well as tsunami parameters, NAMI DANCE computes
i)
tsunami source from either rupture characteristics or
pre-determined wave form,
ii)
propagation,
iii)
arrival time,
iv)
coastal amplification
v)
inundation (according to the accuracy of grid size),
vi)
distribution of current velocities and their directions at
selected time intervals,
vii)
distribution of water surface elevations (sea state) at selected time intervals,
viii)
relative damage levels according to drag force and impact
force,
ix)
time histories of water surface fluctuations,
x)
3D plot of sea state at selected time intervals from different
camera and light positions, and
xi)
Animation of tsunami propagation between source and target
regions (Yalciner et. al., 2006b, 2007b).
3. FILE/VIEW/BATHYMETRY PANELS
Using “File” menu,
projects can be opened and saved in “.xnp”
format. The project file contains type of input files, transparency percent,
image file, landslide color, color palettes loaded for landscape and water,
multipliers and camera position (also dynamic positions and camera target). User
can save the parameters on 3D Plot panel and can load (Open) using “File” menu
when NAMI DANCE is used next time.
Display of the toolbar and status bar can be selected using
“View” menu.
Determination of Grid Size and Bathymetry Processing
“Bathymetry” window allows determination of grid size and
bathymetry processing.
After entering the maximum and minimum GPS coordinates (lon-lat)
and grid step of your study domain, click “Obtain” button. Then, you can
read/obtain number of grid points in the latitudinal (Northing) and longitudinal
(Easting) directions in your domain (i.e. grid sizes along X and Y directions).
Sea bathymetry must be positive, and topography must be negative.
4. PROCESSING BATHYMETRIC DATA
NAMI DANCE program uses the bathymetry of the area as input data.
The bathymetry of the area is usually stored as data files. This file consists
of three values; x coordinate, y coordinate and the depth values. However data
files are typically randomly spaced files and this data must be converted into
an evenly spaced grid before using as input file of the program. To convert into
a grid file, a program called Surfer is used.
Surfer is a contouring and 3D surface mapping program that runs
under Microsoft Windows. It quickly and easily converts your data into
outstanding contour, surface, wireframe, vector, image, shaded relief, and post
maps. Further information can be found and also purchased at the website of
Golden Software;
http://www.goldensoftware.com .
Below is the procedure for converting the bathymetry data file to
grid file by SURFER.
1. Start Surfer.
2. Click
on the Grid | Data command to display the Open dialog.
3. Specify
the name of the XYZ data file which is the bathymetry data of the area, and then
click OK.
4. In the
Grid Data dialog, specify the parameters for the type of grid file you
want to produce.
The Grid Data Dialog
When
creating a grid file you can usually accept all of the default gridding
parameters
Data Columns
Individually specify the columns for the X data, the Y data, and the Z data.
Surfer defaults to X: Column A, Y: Column B, and Z:
Column C, which represents the x coordinate, y coordinate and the depth
respectively.
Gridding
Method
The
gridding method should be set to Kriging which is the recommended gridding
method with the default linear variogram. This is actually the selected default
gridding method because it gives good results for most XYZ data sets.
Output Grid File
Choose a
path and file name for the grid in the Output Grid File group by clicking
the button
(shown by an arrow). Save Grid As dialog
will be opened. You can type a path and file name or browse to a new path and
enter a file name in the box. TUNAMI N2 and TUNAMI N3 require a specific file
format for the output grid file which is ASCII grid file format. To change the
file format, use the drop down Save as type menu and choose GS ASCII (*.grd)
format as shown below. Then click “Save” and return to Grid Data menu.
ASCII Grid File Format
ASCII grid files [.GRD] contain five header lines that provide
information about the size and limits of the grid, followed by a list of Z
values. The fields within ASCII grid files must be space delimited.
The listing of Z values follows the header information in the file.
The Z values are stored in row-major order starting with the minimum Y
coordinate. The first Z value in the grid file corresponds to the lower left
corner of the map. This can also be thought of as the southwest corner of the
map, or, more specifically, the grid node of minimum X and minimum Y. The second
Z value is the next adjacent grid node in the same row (the same Y coordinate
but the next higher X coordinate). When the maximum X value is reached in the
row, the list of Z values continues with the next higher row, until all the rows
of Z values have been included.
The general format of an ASCII grid file is:
|
Id |
The identification string DSAA that identifies the file as an ASCII grid
file. |
|
nx ny |
nx is the integer number of grid lines along the X axis (columns) |
|
|
ny is the integer number of grid lines along the Y axis (rows) |
|
xlo xhi |
xlo is the minimum X value of the grid |
|
|
xhi is the maximum X value of the grid |
|
ylo yhi |
ylo is the minimum Y value of the grid |
|
|
yhi is the maximum Y value of the grid |
|
zlo zhi |
zlo is the minimum Z value of the grid |
|
|
zhi is the maximum Z value of the grid |
|
grid row 1
grid row 2
grid row 3
……….. |
These are the rows of Z values of
the grid, organized in row order. Each row has a constant Y coordinate. Grid row
1 corresponds to ylo and the last grid row corresponds to yhi(i.e. the first row
in the grid file is the last row on the map). Within each row, the Z values are
arranged from xlo to xhi.
|
The following example grid file is ten rows high by ten columns
wide. The first five lines of the file contain header information. X ranges from
0 to 9, Y ranges from 0 to 7, and Z ranges from 25 to 97.19. The first Z value
shown corresponds to the lower left corner of the map and the following values
correspond to the increasing X positions along the bottom row of the grid file.
This file has a total of 100 Z values.
DSAA
10 10
0.0 9.0
0.0 7.0
25.00 97.19
91.03 77.21 60.55 46.67
52.73 64.05 41.19 54.99 44.30 25.00
96.04 81.10 62.38 48.74
57.50 63.27 48.67 60.81 51.78 33.63
92.10 85.05 65.09 53.01
64.44 65.64 52.53 66.54 59.29 41.33
94.04 85.63 65.56 55.32
73.18 70.88 55.35 76.27 67.20 45.78
97.19 82.00 64.21 61.97
82.99 80.34 58.55 86.28 75.02 48.75
91.36 78.73 64.05 65.60
82.58 81.37 61.16 89.09 81.36 54.87
86.31 77.58 67.71 68.50
73.37 74.84 65.35 95.55 85.92 55.76
80.88 75.56 74.35 72.47
66.93 75.49 86.39 92.10 84.41 55.00
74.77 66.02 70.29 75.16
60.56 65.56 85.07 89.81 74.53 51.69
70.00 54.19 62.27 74.51
55.95 55.42 71.21 74.63 63.14 44.99
Grid Line Geometry
Grid line
geometry defines the grid limits and grid density. Grid limits are the minimum
and maximum X and Y coordinates for the grid. Grid density is usually defined by
the number of columns and rows in the grid. The # of Lines in the X
Direction is the number of grid columns, and the # of Lines in the
Y Direction is the number of grid rows. By defining the grid limits and the
number of rows and columns, the Spacing values are automatically
determined as the distance in data units between adjacent rows and adjacent
columns.
5. Click
OK and the grid file is created. During gridding, the status bar at the bottom
of the Surfer window provides you with information about the progress of
the gridding process.
5. CREATING THE INITIAL WAVE FROM DIFFERENT SOURCES
Source Menu
“Source” window allows creating the initial wave using the fault
parameters. There are two different options as “User defined” and “Rupture”
under the “source” menu as shown in figure below.
“Rupture” Option:
In order to generate the initial wave due to an earthquake;
1. On the “source” menu,
click “Rupture”.
2. In “The name of the bathymetry file (input)” box, enter the name
of the bathymetry file you want to use, or browse to locate the file.
3. In “The name of tsunami source file (output)” box, enter the
name of the output file which is going to be the generated initial wave file,
such as initialwave.grd, or browse to locate the file.
4. In the start point and end point of fault axis boxes, enter the
coordinates of the start and end points of the fault.
5. In the “Parameters of fault” boxes, enter the requested
parameters according to the data of the fault which produced the earthquake.
Definitions of the fault break parameters are:
i)
Epicenter coordinates
ii)
Length of the fault (L)
iii)
The width of the fault (W)
iv)
Strike angle, the direction of the fault axis from North
(Clockwise) (?)
v)
The dip angle (d)
vi)
The rake (slip) angle (?)
vii)
Vertical displacement of the fault (D)
viii)
Focal depth (H)
Rupture characteristics:
Important note: The symbol
on the above figure shows the origin of the movement of the fault planes.
In the “Source/Rupture” panel of NAMI DANCE (in the figure below) epicenter
coordinates are assumed to be located at the origin ( ) by NAMI DANCE.
6. Click “Run” to generate the initial wave.
7. If you want to save the parameters, click “Save”. The window
will be closed. In order to generate the initial wave, open the seismic fault
window and click “Run”.
“User Defined” Panel:
In order to generate an initial wave due to an impact or another
arbitrary disturbance in elliptical shape with leading elevation or depression
wave condition, you can use user defined option.
1. On the “source” menu, click “user defined”.
2. In “The name of the bathymetry file” (input) box, enter the name
of the bathymetry file you want to use, or browse to locate the file.
3. In “The name of tsunami source file” (output) box, enter the
name of the output file which is going to be the generated initial wave file,
such as initialwave.grd, or browse to locate the file.
4. Enter the “grid step” which is the distance between two grid
nodes of the bathymetry file in meters.
5. Enter “amplitude of center”, “length of major axis” and “length
of minor axis”, “amplitude of leading wave” and “width of leading wave”. Don’t
forget to put a tick in the box near “for simulation with leading wave” option.
These parameters are shown in the figures below.
TOP VIEW
Wl :
Width of the leading wave
Lmajor
: Length of the major axis
Lminor
: Length of the minor axis
SIDE VIEW
ac : amplitude at
center
6. Click “Run” to generate the initial wave.
7. If you want to save the parameters, click “Save”. The window
will be closed. In order to generate the initial wave, open the “test fault”
window and click “Run”.
Sea bottom subsidence may be observed along the strike slip faults
at some locations where the step over occurs. This is called pull apart
mechanism.
Figure 4.2 Subsidence at the tensile stress area
6. GENERATING THE
“Tsunami simulation” option is used in order to generate the sea
state at specific time intervals of tsunami.
1. On the “tsunami simulation” menu, click “simulate”.
2. Browse for tsunami source file.
3. Enter the time when the disturbance occurs. If it is an
earthquake, this is the time the fault is broken.
4. Click “Add Source”
5. If there is more than one source of disturbance at different
times for the event, repeat the steps above until all the source files are
listed on the menu.
6. If there are “Discharge fluxes in X/Y direction”. Browse them
also in the discharge fluxes section.
7. Click “Next”.
1. Enter the name of the bathymetry file in the “Bathymetry file
name” box or browse for the location of the file.
2. Enter the name of the gauge file in the “Gauges filename” box or
browse for the location of the file. You do not need to enter gauge file to
perform the calculation. Gauge file is needed only when sea state at a specific
coordinate is wanted.
3. To obtain the time step for calculation use the “Obtain time
step” option. Enter the grid size of the bathymetry file. Click “Obtain”. The
program will automatically get the maximum depth and calculate the time step.
4. Enter the obtained time step in the “time step” box. Use a
smaller time step than the obtained value.
5. Enter the start and end time of the simulation in the “time
start” and “time end” boxes in
6. Enter the time step for the output files in the “output file
time step” boxes which will show the sea state at the entered time intervals.
7. Enter the “wall depth”. Wall depth is a depth where a vertical
impermeable barrier is located. No wave motion is permitted behind this barrier.
If you want to put a barrier at land, insert
negative depth.
8. Click “Simulate”.
9. After the simulation ends, close the box.
Important Note:
It is essential that the User must enter the spatial grid size
value of the bathymetry file. The spatial grid size is obtained from INF Button
at left of the bathymetry file name box. The OBTAIN Button must be clicked to
obtain the maximum value of the
siulation time step for avoiding instability.
Note: In “More options” section, Froude number, current velocities and discharge fluxes
can be computed at every grid point at specified time intervals if the check
boxes are checked by the user. The maximum values of these parameters computed
during simulation are also stored by NAMI DANCE at the end of the simulation.
“Runup” Menu
When you click run up button, NAMI DANCE opens the following panel
in which the maximum values (+ve amplitudes) of the water surface computed
throughout the simulation (file name OUT-TIME-HISTORIES.grd) must be opened from
the respective BROWSE button. (First ROW)
The user must also assign a file name by using the BROWSE button on
the second row for storing the maximum +ve amplitudes near the shoreline of the
selected rectangular area. The borders of the rectangular area are inputted by
filling the respective boxes below. If the user requires the amplitudes along
horizontal direction (easting) he/she must enable the check box of Along X.
Othervise the checkbox Along Y must be enabled.
Important Note: The run-up module of NAMI DANCE is designed to analyze the
distribution of the maximum tsunami amplitudes inside the selected rectangular
area along the coastal line. There are some limitations of the computations in
run up menu. if the user needs to use runup menu,
it is strogly recommended that the user must contact the developers.
8. CALCULATING DISTRIBUTION OF RUN-UPS
1. On the distribution menu, go to “1 event” to calculate the
distribution of the run-up for one event or go to “All event” to calculate the
distribution of run-ups for more than one event.
“1 event” option:
1. Enter the name of the run up file on “The runup file name” box
or use browse to locate the file.
2. Put a tick in the “calculate practic.distr?” box if you want to
calculate the practical distribution run up and enter the name of the “practic
distribution file” in the box or use browse to locate the file.
3. Select the “calculate lognorm. distr?” box if you want to
calculate the log normal distribution of run up and enter the name of the “log
normal distribution file” in the box or browse to locate the file.
4. Click “Run”.
Note: In order to use distribution menu please contact the developers.
“All event” option:
1. Enter the name of the run up file on “The Runup file name” box
or use browse to locate the file.
2. Click “add file” to add the selected file to the list.
3. Repeat 1 and 2 until you have all the runup files you need on
the list.
4. To delete a file from the list, select the file that you want to
delete and click “delete file”.
5. Enter the name of the “practic distribution file” in the box or
use browse to locate the file.
6. Enter the name of the “log normal distribution file” in the box
or browse to locate the file.
7. Click “Run” to get both of the distributions for the selected
runup files.
8. Click “OK” to close the box.
Note: In order to use distribution menu please contact the developers.
Important Note:
In order to accelerate visualization capability of NAMI DANCE, it
is strongly recommended that you should check/change 3D Plot settings of your
video card. “24-bit depth buffer”
option in video card settings should be enabled. To enable this option:
-
Open “Display” in Control Panel.
-
On the Settings
tab, click Advanced.
-
Open video card tab, go
to OpenGL settings.
-
Select the check box to
enable “24-bit depth buffer”
All modern video cards support this option. For more information
read manual for your video card.
9.1 Plotting the Sea State at a Specific Time
1. Enter the name of the “bathymetry file in the bathymetry file
name (input)” box or use browse to locate the file. If you want to use a
different color for the topography, select the color by clicking the “color”
button next to the bathymetry file name box.
7
6
5
4
5
2. Put a tick in the box next to
“water file name (input)” box in order to plot the sea state at a specific
time.
3. Enter the name of the water file (input) for the specific time
you want to plot or locate file using browse from sea state (t*******.grd)
files.
4. Water color can be set as transparent by increasing the “Transparency” percentage.
5. Put a tick in the “Enable
palette” box to set the water or landscape color using palette. You can
insert an additional layer or delete an existing one. You can load an available
palette, or modify palette and save for future uses. Palette can be loaded from
“Color” buttons for landscape or water.
6. If the animation contains landslides, put a tick in the “Draw landslides” box.
Note: In order to use
“Draw landslides” menu please contact
the developers, because landslide movement must be prepared in different time
steps.
7. Convenient texture file can be used as topography color by
checking the use “Image” box and
browse for the file to
be used as texture. The texture file may be a satellite image. The file
coordinates must match exactly with bathymetry coordinates. Also, the texture
resolution must be the same with screen resolution.
8. To enter titles for the simulation, use the “title1” and “title2” boxes.
9. Enter the coordinates of the starting point of the titles using
“coordinates of title1” and coordinates of title 2” boxes.
In some applications, if the land topography has very high
elevations and the wave height is not so high comparing to the land topography,
it will not be possible to visualize the tsunami wave and land topography in the
same plane, since there is a high difference between their order of magnitudes.
Therefore, it will be necessary to use a multiplier for land in order to
decrease the heights of topography. The opposite case, that is having high
values for wave amplitude and not significantly high elevations in land
topography. The same procedure also will be applied in this case.
Click on the “Multipliers” button in order to decrease/increase the
heights of certain parameters (see the figure below for “Multipliers” panel).
- Enter a value in the “multiplier of topography” box to
decrease/increase the heights of the topography.
- Enter a value in the “multiplier of wave amplitude” box to
increase the height of the waves to get a well defined sea state.
- Enter a value in the “multiplier of bathymetry” box to
decrease/increase the heights of the bathymetry.
- Enter a value in the
“truncation level of land topography” box if you want to truncate the higher
mountains or to have a certain truncated level after high elevations. This
application provides not to plot the higher mountains and only show them at a
certain truncated level approximately at the amount of hundred meters. These
multipliers do not alter the original calculations.
9.1.2
Preparing BMP Plots for Animation
1. Enter the name of the bathymetry file in the
“bathymetry file name (input)” box or
use browse to locate the file. If you want to use a different color for the
topography, select the color by clicking the color button next to the bathymetry
file name box.
2. Put a tick in the box near “avi preparation” option in order to plot several sea state files having a
specific time interval.
3. Enter the start and end time of the simulation in seconds. You
can either start the simulation when t is 0 or at any second within the duration
of original simulation time. In order to produce plots of sea states at
different times, you must use the times of the output grid (t******.grd) files.
4. Enter the time step for simulation. This number should be equal
to or multiplier of the time step used in the output water file time step.
5. To enter titles for the simulation, use the “title1” and “title2” boxes.
6. Enter the coordinates of the starting point of the titles.
7. Enter the multipliers as described in case 6 in “TO PLOT THE SEA
STATE AT A SPECIFIC TIME” part.
8. In order to show the time of the sea state, select the “show
time?” box and chose the unit of time.
10. Select “OK”.
9.2 Sample Applications for Indicating the Effect of
Multipliers on Visualization
Trial 1:
Multiplier of topography (m) = 0.008
Multiplier of wave amplitude (m) = 15
Multiplier of bathymetry (m) = 1
Truncation level of land topography (m) = 8000
Result 1:
Trial 2:
Multiplier of topography (m)= 0.1
Multiplier of wave amplitude (m)= 15
Multiplier of bathymetry (m)= 1
Truncation level of land topography (m)= 8000
Result 2:
Trial 3:
Multiplier of topography (m)= 0.008
Multiplier of wave amplitude (m)= 50
Multiplier of bathymetry (m)= 1
Truncation level of land topography (m)= 8000
Result 3:
Trial 4:
Multiplier of topography (m)= 0.008
Multiplier of wave amplitude (m)= 15
Multiplier of bathymetry (m)= 1
Truncation level of land topography (m)= 1
Result 4:
-
On “3D Plot (AVI NAMI)”
menu, go to “Camera Position” option.
2. Enter coordinates in the coordinate boxes to locate the camera
to get the desired view of the output files.
Figure: Location of the camera and target point
3. Enter values in the Turn object to turn the output file to get the desired view
of the output files.
4. Enter coordinates of the light in the Light source position
boxes to locate the light source to get the desired view of the output files.
5. Click “OK”.
6. On “3D Plot (NAMI DANCE)” menu, go to “Plot” to plot the output
files with the selected properties of view. This plotting may take some time.
7. After plotting, the location of the image can be changed by
using mouse. Scroll button can be used for zooming in and out.
9.4 Creating Animations from the Output Files
1. First plot output files for animation using the guideline given
above.
2. On “3D plot (AVI-NAMI)” menu, go to “BMP to AVI” option.
3. Enter the name of the
directory or locate it by clicking the “…” button next to the “directory” box.
Once this name is entered, the program automatically shows the bmp files in this
directory as a list in the “Files” box.
4. By default, BMP option
is selected. If not, select the “BMP” option on the “Input Options” menu.
5. If you want to insert
music to the animation, enter the name of the file in the “Wav File” box or
locate the file using the “…” button.
6. Enter the name of the
avi file in the “Avi File” box which is going to be the output simulation file
or locate it using “….” button.
7. Enter the frame rate
and the key rate on output options menu.
8. Click “Create”.
9. Select a type of
compressor (codec) to create the simulation file. The types of codec depend on
the types of codec you have in your hard disk. Change the codec settings to get
the desired view for the simulation.
10. Click “OK” to
generate the simulation.
10. CREATING A
GAUGE POINT FILE
As given above, if the
time histories of water surface fluctuations at selected location (gauge points)
are needed, the file containing the name and coordinates of the gauge points can
be prepared externally or by NAMI DANCE In order to create the gauge file by
NAMI DANCE there are two options i) “gauge point” and ii) “gauge installation“
under Gauge Edit panel.
“gauge point locator” option:
1. On “gauge edit” menu,
go to “gauge point locator” option.
2. Enter the name of the
bathymetry file in “The bathymetry file path” box or use the “browse” option for
locating the file. Click on the box next to it.
3. Enter the name of the
gauge point file in “The gauges point file path” box in which the coordinates of
the locations will be stored or locate the file using browse option. Click on
the box next to it.
4. Click “OK”.
5. The screen will show
the bathymetry file.
6. Click the location you
want to add to the gauge file on the screen.
7. Write the name of the
location in the box appeared on the screen and click “OK”. Then it saves the
cordinate and name of the location in the gauge file.
“gauge installation” option:
This option is developed
if the user needs to locate the gauge points at a certain depth inside a certain
rectangular area. The depth and the corners of the rectangular area can be
inputted by this option as described
in the following.
1. On “gauge edit” menu,
go to “gauge installation” option. Gauge file autocreator will appear.
2. Enter the name of the
bathymetry file in “bathymetry filename” box or use the “browse” option for
locating the file. Click on the box next to it.
3. Enter the name of the
gauge point file in “gauges filename” box in which the coordinates of the
locations will be stored or locate the file using browse option. Click on the
box next to it.
4. Enter a value for the
required depth of the gauge points near “Depth” box.
5. Enter a value for the
distance between the adjacent gauge points near the “Step” box.
6. Enter north, south,
east and west borders of the area where gauge points will be selected from.
7. Click “Start” and the
gauge point file should appear in the selected directory.
“OUT SUMMARY SHEET”
In order to obtain “OUT SUMMARY RESULTS” file OUT TIME HISTORIES
and gauges files must be inserted using Browse button. After selecting an
elevation for detection of the first wave in meters is also entered, click
“Run”. “OUT SUMMARY RESULTS.dat” file
should appear in the respective directory. This file contains the coordinates
and depths of gauge points, the arrival times of first and maximum waves and
maximum negative and positives wave amplitudes occuring at the gauge points.
This file is also considered as the summary sheet of the simulation results.
NAMI DANCE can also generate a file named OUT-SUMMARY-INPUT.dat
which shows the user’s selections and inputted paarmeters or files used in the
simulation.
GAUGES FILE DETAILS
The gauge location data is saved as *.dat file and contains the
names, x and y coordinates of the gauge locations within the area. Names of the
locations will be written without having any space between words and without
quotation marks. Next, the x coordinate and the y coordinate of the location
will be written in decimals. There should be space between the name of location,
x coordinate and y coordinate. Do not use tab button for having space between
location name and coordinates that the program cannot read the gauge file
properly. South and west coordinates will be shown with a minus sign. A sample
gauge file is shown in the figure below:
From “Convert” menu, conversions from ‘NetCDF to GRD’ , ‘GRD to
NetCDF’ and “GRD to DAT” are possible.
There are two types of conversion. First conversion type is for
bathymetry files. The bathymetry file without any extension (for example “gridA.”) can be converted to
“bathymetry.grd”. Next conversion type
is for water elevation files.
“t******.grd” files can be extracted from files with extension
“.nc”. Also bathymetry or water elevation “*****.grd” files can be converted
to XYZ format “*****.dat” files.
Browse for input and output (export) files.
Click ‘Run’ to start and
click “Stop” to cancel the operation.
Note: In order to proper use of “Convert” menu, please contact the developers.
NAMI DANCE is developed by Dr. Andrey Zaytsev in collaboration with
Anton Chernov, Ahmet Cevdet Yalciner, Efim Pelinovsky, and Andrey Kurkin. In the
development process of NAMI DANCE, research assistants Isil Insel, Derya Itir
Dilmen, Ceren Ozer, Ayse Karanci, Gulizar Ozyurt, Hulya Karakus, Mustafa Esen,
and Cuneyt Baykal have taken part for testing, and commenting. All developers
and contributors of NAMI DANCE acknowledge Prof. Nobuo Shuto, for his long term,
endless cooperation, contribution and support throughout the development of the
code described in this manual. Prof. Fumihiko Imamura, Prof. Costas E.
Synolakis, Prof. Emile Okal, are also acknowledged by Dr. Yalciner for their
long term close collaborations, help and cooperation.
Development of this code has been supported by INTAS (grant number
INTAS YSF Ref. No:05-109-5100), European Commission Project
TRANSFER (Tsunami Risk And Strategies For European Region),
Nizhniy Novgorod State Technical University, Department of Computer
Sciences, and Middle East Technical University, Civil Engineering Department,
Ocean Engineering Research Center.
GOTO, C. AND OGAWA, Y., (1991), "Numerical Method of Tsunami
Simulation With the Leap-Frog Scheme", Translated for the TIME Project by Prof.
Shuto, N., Disaster Control Res.
Cent., Faculty of Engg.,
OKADA, Y., (1985), Surface deformation due to shear and tensile
faults in a half-space, Bull. Seism. Soc.
SHUTO, N., GOTO, C., IMAMURA, F., 1990.
Numerical simulation as a
means of warning for near field tsunamis. Coastal. Engineering in
IMAMURA F., (1989),
“Tsunami Numerical Simulation with the staggered leap-frog scheme (Numerical
code of TUNAMI-N1)”, School of Civil Engineering, Asian Inst. Tech. and
YALCINER A,. C., (2005) “Marine Hazards and Tsunamis”, CE 761
Course Notes, Middle East Technical University Civil Engineering Department,
webpage: yalciner.ce.metu.edu.tr/courses/ce761
www.pmel.noaa.gov/tsunami-hazard/terms.html
vulcan.wr.usgs.gov/Glossary/ Seismicity/earthquake_terminology.html
www.seismo.berkeley.edu/faq/gloss_0.html
SYNOLAKIS C.E., BERNARD E.N., TITOV V., KÂNOGLU U., GONZÁLEZ F.,
(2007), Standards, Criteria, And Procedures For NOAA, Evaluation Of of Tsunami
Numerical Models, NOAA Technical Memorandum OAR PMEL-135
NOAA web site:
http://www.pmel.noaa.gov/pubs/PDF/syno3053/syno3053.pdf
NOAA, (2007), Tsunami Vocabulary and Terminology NOAA web site:
http://www.tsunami.noaa.gov/terminology.html
UNESCO (2006), Tsunami Glossary,
UNESCO-IOC. IOC Information document No. 1221 Printed by Servicio Hidrográfico y
Oceanográfico de la Armada (SHOA) Errázuriz 254 Playa Ancha Valparaíso Chile
Published by the United Nations Educational, Scientific and Cultural
Organization 7 Place de Fontenoy, 75 352 Paris 07 SP, France © UNESCO 2006.
Paris, UNESCO, 2006.
YALCINER, A.C., KARAKUS, H., OZER, C., OZYURT, G., (2005), “Short
Courses on Understanding the Generation, Propagation, Near and Far-Field Impacts
of TSUNAMIS and Planning Strategies to Prepare for Future Events” Course Notes
prepared by METU Civil Eng. Dept.
Ocean Eng. Res. Center, for the Short Courses in University of Teknology
Malaysia held in Kuala Lumpur on
July 11-12, 2005, and in Astronautic Technology Malaysia held in Kuala Lumpur on
April 24-May 06, 2006, and in UNESCO Training on Tsunami Numerical Modeling held
in Kuala Lumpur on May 08-19 2006 and in Belgium Oostende on June 06-16, 2006.
KURKIN, A.A., KOZELKOV, A.C., ZAITSEV A.I., ZAHIBO N., AND YALCINER
A.C. (2003): Tsunami risk for the
SYNOLAKIS, C. E, LIU, P. L. F., YEH, H. (2004): Workshop on Long
Wave Runup Models, Organized by NSF in Catalina Island LA,
YALCINER, A.C., KURAN, U., AKYARLI, A. AND IMAMURA, F., (1995): An
Investigation on the Generation and Propagation of Tsunamis in the Aegean Sea by
Mathematical Modeling, Chapter in the Book, "Tsunami: Progress in Prediction,
Disaster Prevention and Warning", in the book series of Advances in Natural and
Technological Hazards Research by Kluwer Academic Publishers, (1995), Ed.
Yashuito Tsuchiya and Nobuo Shuto, pp 55-71
YALCINER, A.C., ALPAR, B., ALTINOK, Y., OZBAY, I., IMAMURA, F.,
(2002a): Tsunamis in the
YALCINER, A.C., PELINOVSKY, E.N., TALIPOVA, T.G., KURKIN, A.A.,
KOZELKOV, A.C., ZAITSEV, A.I., (2002b):
A. Tsunamis in the
YALCINER, A.C., IMAMURA, F., SYNOLAKIS, E.C., (2002b): Simulation of Tsunami Related to Caldera
Collapse and a Case Study of Thera Volcano in Aegean Sea, Abstract Published and
paper presented in EGS XXVII General
Assembly, Nice, France, April 2002 Session NH8.
YALCINER, A.C., KARAKUS, H., KURAN, U., (2006a): Modeling of
Tsunamis in the Eastern Mediterranean and Comparison with Caribbean,
YALCINER, A. C., PELINOVSKY, E., ZAYTSEV, A., KURKIN, A., OZER, C.,
AND KARAKUS, H., (2006b): NAMI DANCE Manual, METU, Civil Engineering Department,
Ocean Engineering Research Center, Ankara, Turkey (http://namidance.ce.metu.edu.tr)
YALCINER, A. C., PELINOVSKY, E., ZAYTSEV, A., KURKIN, A., OZER, C.,
AND KARAKUS, H., (2007a): Modeling and visualization of tsunamis: Mediterranean
examples, from, Tsunami and Nonlinear Waves (Ed: Anjan Kundu), Springer, 2007,
2731-2839.
YALCINER, A. C., SYNOLAKIS, C. E: , GONZALES, M., KANOGLU, U., (2007b): Joint Workshop on
Improvements of Tsunami Models, Inundation Map and Test Sites of EU TRANSFER
Project, June 11-14,
ZAHIBO, N., PELINOVSKY, E., YALCINER, A.C., KURKIN, A., KOZELKOV A.
AND ZAITSEV, A., (2003a): The 1867
ZAHIBO, N., PELINOVSKY, E., KURKIN, A., AND KOZELKOV A. (2003b):
Estimation of far-field tsunami potential for the
This document has been prepared as
Deliverable of TRANSFER Tsunami Risk ANd Strategies For the European Region
Instrument: STREP Thematic Priority: Mechanisms of desertification and natural
disasters
Project no. 037058
(GOCE)
State-of-the-art and
Phases of Tsunami
Modeling
Tsunami is one of the most important
marine hazards generally triggered by earthquakes and/or submarine/subaerial
landslides. In general, tsunami might affect not only the area where it is
generated but substantial distance away from generation region. Tsunami science
needs close cooperation between basic and applied sciences and also from
international to local level authorities.
The tsunami modeling and risk analysis are necessary for better
preparedness and proper mitigation measures in the framework of international
collaborations. Better understanding, wider awareness, proper preparedness and
effective mitigation strategies for tsunamis need close international
collaboration from different scientific and engineering disciplines with
exchange and enhancement of existing data, development and utilization of
available computational tools.
Modeling is one of the essential
components of tsunami studies in scientific and operational level. Tsunami
modelling has several phases in which exchange and enhance of available
earthquake and tsunami data, bathymetric and topographic data in sufficient
resolution, selection of possible or credible tsunami scenarios, selection and
application of the validated and verified numerical tools for tsunami
generation, propagation, inundation and visualization must be covered.
In general, there are several unique phases of tsunami modeling for
a specific region. They are summarized in the following.
Phase 1: Catalogue and literature survey on the historical tsunamis
Catalogue and literature survey must be done and the followings
must be delivered.
The paleotsunami study (coastal trench study) by the expert
paleotsunami geologist(s) at the selected region(s) must also be kept in the
agenda which may provide some findings about traces of some historical tsunami
events for comparison and assessment of the level of historical events.
Main deliverables must be:
i) The length of
historical time for which tsunami reports and records,
ii) Evaluation of
reliability of the historic documents,
iii) Estimates of run-up heights of historical events from the
collected data and information and paleotsunami studies.
Phase 2:
Determination/development of bathymetry/topography data
The bathymetric and topographic data in digital form from available
navigational charts, conventional and multi beam bathymetric measurements,
digital elevation models, satellite images must be collected and
bathymetry/topography for the region must be developed. The coordinates of
existing shoreline, nearshore bathymetry and land topography must also be
measured and added to the bathymetry topography database. The database must also be in
sufficient resolution
in GIS based format,
especially nearshore and
shallow regions with an accuracy of at least less than 50m and 1-5m in
horizontal and vertical dimensions respectively.
Main deliverables must be:
i) Digital data of bathymetry and
topography in sufficient accuracy and in GIS based format.
Phase 3: Determination of current land use plans in GIS based format
The digital land use plans of the study
area in GIS format are necessary for accurate and applicable results of tsunami
modelling. The distribution of coastal and marine structures must be located in
the plans.
An example list of important structures can be; residential buildings, commercial
centers, industrial plants, open areas, educational buildings, health services,
social, historical, cultural and public areas/buildings, monuments, fire
stations, offices of security service, communication centers, infrastructures
near shoreline (waste water discharge systems, fresh and waste water network),
support units, transportation structures (piers, breakwaters, coastal protection
structures, all types ports, harbors, marinas, small craft harbors, fishery
harbors, shelters, railway stations, passenger terminals, airport, heliport
etc.), agricultural areas, areas of
solid wastes, treatment plants.
Main deliverables must be:
i)
Digital database of coastal, marine and other important structures in GIS format
together with vulnerability levels.
ii) Building density map.
Phase 4:
Determination and characterization of probable tsunami sources,
Characteristics, dimensions and locations of near field and far
field submarine and/or coastal faults and landslide prone regions must be
identified and
i)
Inventory of near (<50 km) and far (>50 km) tsunamigenic (tectonic
and slope-failure related) sources,
ii)
Characterization of tsunami faults,
iii)
Characterization of identified unstable bodies, submarine
landslides and possible tsunamigenic seafloor deformations must be determined.
This is a difficult task and needs much discussion among marine geologists and
earth scientists, since uncertainties in the underlying fault rupture and
landslide processes are large.
Main deliverables must be:
i) Fault maps,
ii) Submarine/subaerial landslide maps,
Phase 5: Computing the tsunami source characteristics from using estimated rupture
characteristics and landslide characteristics
Developing and/or using valid, verified, advanced computational
tools for computing the tsunami source parameters with sufficient accuracy and
reliability as for the input of tsunami modeling.
Main deliverable must be:
i) Initial fluid displacements and velocity fields of the tsunami
sources.
Phase 6: Determination of study domains for modeling
Nested grid system covering nearfield
and far field sources and also the coastal communities must be to be generated.
Main deliverable must be:
i) Digital data of bathymetry and
topography of each study domain in sufficient accuracy and required format.
Phase 7: Simulation and computing all necessary tsunami parameters
Phase 5 provides data of the initial conditions of tsunami source
(i.e., initial fluid displacements and velocity fields), for the computational
model(s) to be used propagation of tsunamis in the open sea and their coastal
amplification and runup at shallower regions and on land in the study regions.
This phase is the most important phase of tsunami modeling, since scientific
based techniques and tools are essential for the best possible quantification.
Use state-of-the-art numerical models to simulate tsunami
propagation from the source to shoreline and runup location. This phase must
briefly cover
i)
tsunami scenarios
ii)
use of validated and verified tsunami propagation and inundation
model(s)
iii)
simulation and analysis of relevant historical tsunamis,
iv)
simulation of predefined tsunami scenarios and their analysis,
v)
tsunami impact micro zoning,
vi)
Inundation mapping for selected coastal regions.
The main deliverables of tsunami
simulations are
i) Tsunami propagation maps for selected scenarios
ii) Time histories of water level fluctuations at selected
locations
iii) Arrival time distributions of first wave along shoreline
iv) Arrival time distributions of maximum wave along shoreline
v) Distributions of magnitude and direction of maximum currents
vi) Distributions of maximum positive amplitudes
vii) Distributions of maximum negative amplitudes
viii) Distribution of inundation distances
ix) Distributions of relative impact forces
Phase 8: Inundation Mapping
The maps providing the information of the estimated hazard zone
parameters such as design flow elevation (DFE) and maximum velocity, related to
deterministic and probabilistic tsunami scenarios must be prepared according to
the numerical outputs of tsunami modeling.
These maps give comparisons of these estimates with one another and with
the available manuals and guidelines and also show estimated borders of
inundation.
Phase 9: Probabilistic analysis
Probability of occurrence of each tsunami source must be
determined. By compilation of the model results of each scenarios, the
probabilities of certain runup and inundation distances of tsunamis near the
coastal region of the project must be determined in this task.
Phase 10: Dissemination of Results
In order to define the probable effects of tsunamis along its
probable inundation areas, the coastal topography with land use plans, showing
sensitive and vulnerable regions and structures must be taken into account.
Using the probabilistic and/or deterministic approaches and their results on
arrival time, maximum positive amplitudes near shoreline, shoreline velocities
and estimated runup and inundation distances, the potential effects of probable
tsunamis must be estimated for the preparedness issues.
Phase 11: Animations and 3D visualizations of selected tsunami scenarios
By using advanced numerical modeling for visualization, awareness,
preparedness and dissemination of the results and making them to be wider
applicable, there must be the series of audio-visual products and
educational/training materials showing the behavior and possible effects of
tsunamis in the region.
Maps, visual materials are used
and by using advanced animation programs, the propagation of selected
tsunami(s) and its arrival to coastal regions will be shown as 3D movies for the
educational purposes.
The main deliverables are:
i) The database of all processed and produced data,
ii) Illustrative maps,
iii) Visual materials 2 and/or 3D still images and video
animations,
iv) Educational and training materials
Phase 12: Providing data and specific information to authorities for developing
guidelines and mitigation measures in accordance with the land use plans
In terms of provisions of technical codes for the coastal and
marine structures and facilities, the development of codes and standards for
infrastructures against hazards is a problem at international level.
Using estimated runup values, coastal and overland velocities, and
their estimated frequency of occurrences to express the modeling results and
consider the distribution of vulnerability, sensitivity and importance of
coastal and marine structures, the specific methods and work plan must be proposed for better understanding,
awareness, preparedness and proper mitigation measures for the authorities and
experts.
GLOSSARY IN TSUNAMI MODELLING
Aftershock:
An earthquake that
follows a larger earthquake or main shock and originates at or near the focus of
the larger earthquake. Generally, major earthquakes are followed by a larger
number of aftershocks, decreasing in frequency with time.
Amplitude: The rise above or drop
below the ambient water level as read on a tide gage.
Arrival time: Time of arrival,
usually of the first wave, of the first wave of the tsunami at a particular
location.
Attenuation - a reduction in wave
amplitude.
Average period (Tav, Tz) - Average zero
down-crossing wave period. The average period of the waves observed, weighted by
wave energy.
Average Wave Height
(Hav) - Average zero
down-crossing wave height. The average height of the waves observed.
Breaker - A wave that has
reached maximum steepness and is breaking.
Body wave:
A seismic wave that
travels through the interior of the earth and is not related to a boundary
surface.
Bore: Traveling wave with an abrupt vertical
front or wall of water. Under certain conditions, the leading edge of a tsunami
wave may form a bore as it approaches and runs onshore. A bore may also be
formed when a tsunami wave enters a river channel, and may travel upstream
penetrating to a greater distance inland than the general inundation.
Capillary Wave - A wave in which the
velocity of propagation is a function of the surface tension of the water. Wind
waves of wavelength less than about
Continental Crust:
Outermost solid layer of
the earth that forms the continents and is composed of igneous, metamorphic, and
sedimentary rocks. Overall, the continental crust is broadly granitic in
composition. Contrast with oceanic crust.
Continental Drift:
The theory, first
advanced by Alfred Wegener, that the earth's continents were originally one land
mass called Pangaea. About 200 million years ago Pangaea split off and the
pieces migrated (drifted) to form the present-day continents. The predecessor of
plate tectonics.
Convergent Plate Boundary:
See subduction, and subduction zone.
Crest - The highest point on a wave.
Crest Period (Tc) - the average time
between successive maxima, or crests. Calculated from moments of wave frequency
spectrum as Tc = square root of (m2/m4) .
Crust:
The outer layer of the
earth's surface.
Deep Water Wave - A wave for which water
depth is greater than one half the wave length. Ocean wind waves are negligibly
affected by the bottom in deep water.
Dip:
The angle between
a geologic surface-for example, a fault plane-and the horizontal. The direction
of a dip can be thought of as the direction a ball, if placed upon the tilted
surface, would roll. Thus, a ball placed on a north-dipping fault plane would
roll northward. The dip of a surface is always perpendicular to the strike of
that surface.
Diffraction - A wave process in
which energy is transmitted along wave crests. When a wave train passes a
barrier, diffraction causes energy to propogate into sheltered regions behind
the barrier.
Dispersion of Waves - The tendency of longer
waves to travel faster than shorter waves due to the proportionality between
wave phase speed and wave length.
Divergent Plate Boundary:
The boundary between two crustal plates that are pulling apart (e.g. sea floor
spreading).
Dominant Wave Period - The period
corresponding to the frequency of maximum variance as represented by a wave
frequency spectrum.
Duration - In terms of wave
growth, the time over which the wind blows at a constant velocity.
Earthquake:
Shaking of the earth
caused by a sudden movement of rock beneath its surface.
Earthquake swarm:
A series of minor
earthquakes, none of which may be identified as the main shock, occurring within
a limited area and time.
Elastic wave:
A wave that is propagated
by some kind of elastic deformation, that is, a deformation that disappears when
the forces are removed. A seismic wave is a type of elastic wave.
Epicenter:
That point on the earth's
surface directly above the hypocenter of an earthquake.
ETA: Estimated Time of Arrival. Computed
arrival time of the first tsunami wave at coastal communities after a specific
earthquake has occurred.
Fault:
A weak point in the
earth's crust where the rock layers have ruptured and slipped.
Fetch - In terms of wave growth, the distance on
the ocean over which the wind blows at a constant velocity.
First arrival:
The first recorded signal
attributed to seismic wave travel from a known source.
First motion: Initial motion of the
first wave, a rise in the water level is denoted by R, a fall by F.
Focal zone:
The rupture zone of an
earthquake. In the case of a great earthquake, the focal zone may extend several
hundred kilometers in length.
Focus:
That point within the
earth from which originates the first motion of an earthquake and its elastic
waves.
Foreshock:
A small tremor that
commonly precedes a larger earthquake or main shock by seconds to weeks and that
originates at or near the focus of the larger earthquake.
Free field offshore profile: A profile of the wave measured far enough offshore so that it is unaffected by
interference from harbor and shoreline effects.
Frequency - a measure of the
number of oscillations or cycles per unit time; the reciprocal of the time
duration (period) of an oscillation. (A wall outlet in
Gravity Wave - A wave in which the
velocity of propagation is a function of gravity. Water waves over a few inches
in length are considered gravity waves.
Group Velocity - The velocity at which
wave energy propagates. In deep water, it is equal to half the velocity of the
induvidual waves in the group.
Harbor resonance: The continued
reflection and interference of waves from the edge of a harbor or narrow bay
which can cause amplification of the wave heights, and extend the duration of
wave activity from a tsunami.
Harmonic - a quantity whose
frequency is an integral multiple of the frequency of a periodic quantity to
which it is related.
Height - The vertical distance between a wave
crest and the next wave trough.
Horizontal inundation distance: The distance that a tsunami wave penetrates onto the shore, measured horizontally
from the mean sea level position of the water's edge. Usually measured as the
maximum distance for a particular segment of the coast.
Harmonic Tremor:
A continuous release of
seismic energy typically associated with the underground movement of magma,
often preceding volcanic eruptions. It contrasts distinctly with the sudden
release and rapid decrease of seismic energy associated with the more common
type of earthquake caused by slippage along a fault.
Hypocenter:
The calculated location
of the focus of an earthquake.
ICG/ITSU: The International
Coordination Group for the Tsunami Warning System in the Pacific, a United
Nations organization under UNESCO responsible for international tsunami
cooperation.
Intensity:
A measure of the effects
of an earthquake at a particular place on humans and/or structures. The
intensity at a point depends not only upon the strength of the earthquake
(magnitude) but also upon the distance from the earthquake to the epicenter and
the local geology at that point.
Inundation: The depth, relative to
a stated reference level, to which a particular location is covered by water.
Inundation area: An area that is flooded
with water.
Inundation line (limit): The inland limit of
wetting measured horizontally from the edge of the coast defined by mean sea
level.
Intermediate Water Wave - A term used to
describe waves that are neither deep water nor shallow water waves. For both of
these cases, equations for waves can be easily approximated. Waves are usually
considered in intermediate water when the ratio of the water depth to wave
length is between about 1/20 and one half ( 1/2 ) .
ITIC:
Kinetic energy - the energy of an
object or parcel of fluid by virtue of its motion. Kinetic energy is
proportional to mass and the square of the speed.
Leading-depression wave: Initial tsunami wave is
a trough, causing a draw down of water level.
Leading-positive wave: Initial tsunami wave is
a crest, causing a rise in water level. Also called a leading-elevation wave.
Leeward - The direction toward
which the wind and waves are going.
Liquefaction:
The process in which a
solid (such as soil) takes on the characteristics of a liquid as a result of an
increase in pore pressure and a reduction in stress. In other words, solid
ground turns to jelly.
Lithosphere:
The rigid crust and
uppermost mantle of the earth. Thickness is on the order of
Local/regional tsunami: Source of the tsunami
within
method in the TriAxys Directional Wave Buoy.
Marigram: Tide gage recording
showing wave height as a function of time.
Marigraph: The instrument which
records wave height.
Maximum wave height (Hmax) - This is the
largest peak to trough height seen during a record. Mean zero down-crossing wave
height.
Mean Lower Low Water (MLLW): The average low tide water elevation often used as a reference to measure runup.
Mean Wave Direction (Dm)- Overall mean wave
direction in degrees obtained by averaging the mean wave angle (theta) over all
frequencies with a weighting function S(f). Theta is calculated by the KVH
Ms: Surface Wave Magnitude. Magnitude of an earthquake as measured from the amplitude of seismic surface
waves. Often referred to by the media as "Richter" magnitude.
Mw: Moment Magnitude. Magnitude based on the
size and characteristics of the fault rupture, and determined from long-period
seismic waves. It is a better measure of earthquake size than surface wave
magnitude, especially for very large earthquakes. Calibrated to agree on average
with surface wave magnitudes for earthquakes less than magnitude 7.5.
Magma:
Molten rock beneath the
surface of the earth. Molten rock erupted at the surface is termed "lava."
Magnitude:
A quantitative measure of
the strength of an earthquake. Magnitude is calculated from ground motion as
measured by seismograph and incorporates the distance of the seismograph from
the earthquake epicenter so that, theoretically, the magnitude calculated for an
earthquake would be the same from any seismograph station recording that
earthquake. This is a logarithmic value originally defined by Wadati (1931) and
Richter (1935). An increase of one unit of magnitude (for example, from 4.6 to
5.6) represents a 10-fold increase in wave amplitude on a seismogram or
approximately a 30-fold increase in the energy released. In other words, a
magnitude 6.7 earthquake releases over 900 times (30 times 30) the energy of a
4.7 earthquake - or it takes about 900 magnitude 4.7 earthquakes to equal the
energy released in a single 6.7 earthquake! There is no beginning nor end to
this scale. However, rock mechanics seem to preclude earthquakes smaller than
about -1 or larger than about 9.5. A magnitude -1.0 event releases about 900
times less energy than a magnitude 1.0 quake. Except in special circumstances,
earthquakes below magnitude 2.5 are not generally not felt by humans. See also
Richter scale.
Major earthquake:
An earthquake having a
magnitude of 7 or greater on the Richter scale.
Mantle:
The layer of rock that
lies between the outer crust and the core of the earth. It is approximately
Micro earthquake:
An earthquake having a
magnitude of 2 or less on the Richter scale.
Modified Mercalli Scale:
Mercalli intensity scale modified for North American conditions. A scale, composed
of 12 increasing levels of intensity that range from imperceptible shaking to
catastrophic destruction, designated by Roman numerals. It does not have a
mathematical basis; instead it is an arbitrary ranking based on observed
effects. Contrast with Richter scale, a type of magnitude scale.
Normal earthquake: An earthquake caused by
slip along a sloping fault where the rock above the fault moves downwards
relative to the rock below.
Oceanic crust:
The outermost solid layer
of Earth that underlies the oceans. Composed of the igneous rocks basalt and
gabbro, and therefore basaltic in composition. Contrast with continental crust.
P (Primary) wave:
Also called compressional
or longitudinal waves, P waves are the fastest seismic waves produced by an
earthquake. They oscillate the ground back and forth along the direction of wave
travel, in much the same way as sound waves (which are also compressional), move
the air back and forth as the waves travel from the sound source to a sound
receiver.
Period: The length of time between two successive
peaks or troughs. May vary due to complex interference of waves. Tsunami periods
generally range from 5 to 60 minutes.
Peak period Tp - The period with the
maximum wave energy, determined from the wave spectrum.
Phase:
The onset of a
displacement or oscillation on a seismogram indicating the arrival of a
different type of seismic wave.
Phase Velocity - Propogation velocity
of an individual wave. In deep water it is proportional to the wave length,
otherwise it depends on water depth.
Plate:
Pieces of crust and
brittle uppermost mantle, perhaps
Plate boundary:
The place where two or
more plates in the earth's crust meet.
Plate tectonics:
A widely accepted theory
that relates most of the geologic features near the earth's surface to the
movement and interaction of relatively thin rock plates. The theory predicts
that most earthquakes occur when plates move past each other.
Rayleigh wave:
A type of surface wave
having a retrograde, elliptical motion at the earth's surface, similar to the
waves caused when a stone is dropped into a pond. These are the slowest, but
often the largest and most destructive, of the wave types caused by an
earthquake. They are usually felt as a rolling or rocking motion and in the case
of major earthquakes, can be seen as they approach. Named after Lord Rayleigh,
the English physicist who predicted its existence.
Recurrence interval:
The approximate average
length of time between earthquakes in a specific seismically active area.
Record interval
- The time between the
start of sequential records, which must be greater than the record length.
Record length - The total time
required to collect the data for a wave record.
Record offset - The time to offset
record start times from the integral multiple of the record interval. For
example if the record interval is 30 minutes, and the record offset is -10
minutes, then records will start 10 minutes before each hour and half hour.
Reflection - The process by which
wave energy is returned in the opposite direction after a wave strikes an object
or a water boundary.
Refraction - The process by which
the direction of a moving wave is changed due to its interaction with the bottom
topography. Wave heights may be increased or decreased by refraction.
Response function - The correction applied
to the spectrum of a record to allow for the frequency dependant errors
introduced by the wave buoy and receiver.
Return Period - The average time
interval between occurences of wave heights equal to or greater than the height
associated with the return period. It is a measure of the infrequentness of
higher wave heights.
Richter magnitude scale:
The system used to measure the strength or magnitude of an earthquake. The Richter
magnitude scale was developed in 1935 by Charles F. Richter of the California
Institute of Technology as a collection of mathematical formulas to compare the
size of earthquakes. A similar scale was developed in 1931 by Wadati, so it is
more appropriate to call such scales "Wadati-Richter" scales. The magnitude of
an earthquake is determined from the logarithm of the amplitude of waves
recorded by seismographs. Adjustments are included for the variation in the
distance between the various seismographs and the epicenters of the earthquakes.
On the Richter Scale, magnitude is expressed in whole numbers and decimal
fractions. For example, a magnitude 5.3 might be computed for a moderate
earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of
the logarithmic basis of the scale, each whole number increase in magnitude
represents a tenfold increase in measured amplitude; as an estimate of energy,
each whole number step in the magnitude scale corresponds to the release of
about 31 times more energy than the amount associated with the preceding whole
number value.
Rift system:
The oceanic ridges formed
where tectonic plates are separating and new crust is being created; also refers
to the on-land counterparts such as the East African Rift.
Ring of Fire:
A
Runup: Maximum height of the water onshore
observed above a reference sea level. Usually measured at the horizontal
inundation limit.
Rupture zone:
The area of the earth
through which faulting occurred during an earthquake. For very small
earthquakes, this zone could be the size of a pinhead, but in the case of a
great earthquake, the rupture zone may extend several hundred kilometers in
length and tens of kilometers in width.
S (secondary, or shear) wave:
A seismic body wave that involves particle motion from side to side, perpendicular
to the direction of wave propagation. S-waves are slower than P-waves and cannot
travel through a liquid such as water or molten rock.
Sample interval - The time between wave
samples. A typical value would be .78125 seconds, or 1.28 Herz for a DATAWELL
wave buoy.
Seafloor Spreading:
The mechanism by which
new oceanic crust is created at oceanic ridges and slowly spreads away as the
plates separate.
Seiche: A standing wave oscillating in a
partially or fully enclosed body of water. May be initiated by long period
seismic waves, wind and water waves, or a tsunami.
Seismic:
Of or having to do with
earthquakes.
Seismic belt:
An elongated earthquake
zone, for example, circum-Pacific, Mediterranean,
Seismic constant:
In building codes dealing
with earthquake hazards, an arbitrarily-set acceleration value (in units of
gravity) that a building must withstand.
Seismicity:
Earthquake activity.
Seismic sea wave:
A tsunami generated by an
undersea earthquake.
Seismic zone:
A region in which
earthquakes are known to occur.
Seismogram:
A written record of an
earthquake, recorded by a seismograph.
Seismograph:
An instrument that
records the motions of the earth, especially earthquakes.
Seismograph station:
A site at which one or
more seismographs are set up and routinely monitored.
Seismology:
The study of earthquakes
and earthquake waves.
Shallow Water Wave - A wave for which the
depth divided by the wave length is less than approximately 1/20. Equations for
waves can be approximated by special equations for such shallow water where
waves are strongly affected by bottom depth.
Shoaling - Changes in wave height
as waves move into shallow water. Except for a limited depth region, shoaling
increases wave heights. Shoaling occurs even if wave heights and directions do
not change as a result of wave refraction.
Significant Wave height (Hs,Hmo, H1/3) - This is
the average of the highest 1/3 of all waves in a time series. It can be
closely approximated from a time series of wave heights as four times the
standard deviation of the time series. The value can also be approximated
from four times the square root of the area under the energy spectrum of a FFT
analysis. This is typically called Hmo.
Significant Wave Period (Ts) - The average
period of the one-third highest waves in a wave record. The significant wave
period is somewhat shorter than the dominant wave period. Calculated from
moments of wave frequency spectrum as Ts = square root of (m0/m1).
In the TriAxys Directional Wave Buoy it is the average period of the significant
zero down-crossing waves(s) .
Slip: The relative displacement of formerly adjacent points on opposite sides of a
fault, measured at the fault surface.
Spectrum - A method of
representing the distribution of wave energy as a function of frequency.
Strike-slip fault:
A nearly vertical fault
with side-slipping displacement.
Strike-slip earthquake: An earthquake caused by
horizontal slip along a fault.
Subduction:
The process in which one
lithospheric plate collides with and is forced down under another plate and
drawn back into the earth's mantle.
Subduction zone:
The zone of convergence
of two tectonic plates, one of which is subducted beneath the other. An
elongated region along which a plate descends relative to another plate, for
example, the descent of the Nazca plate beneath the South American plate along
the Peru-Chile Trench.
Surf - Waves as they reach the area between the
shore and the area where breakers start to occur.
Surface waves:
Waves that move over the
surface of the earth. Rayleigh and Love waves are surface waves.
Swell - Wind waves that have traveled out of a
storm generating area. Swell has longer periods and a smoother appearance than
wind waves in the storm area.
Tectonic:
Pertaining to the forces
involved in the deformation of the earth's crust, or the structures or features
produced by such deformation.
Teletsunami: Source of the tsunami
more than
Thrust earthquake: An earthquake caused by
slip along a gently sloping fault where the rock above the fault is pushed
upwards relative to the rock below. The most common type of earthquake source of
damaging tsunamis.
Tidal wave: Common term for tsunami
used in older literature, historical descriptions and popular accounts. Tides,
caused by the gravitational attractions of the sun and moon, may increase or
decrease the impact of a tsunami, but have nothing to do with their generation
or propagation. However, most tsunamis (initially) give the appearance of a
fast-rising tide or fast-ebbing as they approach shore and only rarely as a
near-vertical wall of water.
TIME: The Center for the Tsunami Inundation
Mapping Effort, to assist the Pacific states in developing tsunami inundation
maps.
Transform Fault:
A plate boundary where
one plate slides past another; essentially a large strike-slip fault.
Tremor:
Low amplitude, continuous
earthquake activity commonly associated with magma movement.
Travel time: Time (usually measured
in hours and tenths of hours) that it took the tsunami to travel from the source
to a particular location.
Trough - The lowest part of the wave between
successive crests.
Tsunami: A Japanese term derived
from the characters "tsu" meaning harbor and "nami" meaning wave. Now generally
accepted by the international scientific community to describe a series of
travelling waves in water produced by the displacement of the sea floor
associated with submarine earthquakes, volcanic eruptions, or landslides.
Tsunami earthquake: A tsunamigenic
earthquake which produces a much larger tsunami than expected for its magnitude.
Tsunamigenic earthquake: Any earthquake which
produces a measureable tsunami.
Tsunami magnitude: A number which
characterizes the strength of a tsunami based on the tsunami wave amplitudes.
Several different tsunami magnitude determination methods have been proposed.
TWS: Tsunami Warning System, organization of
26 Pacific Member States which coordinates international monitoring and warning
dissemination. Operates through ICG/ITSU
UTC: Universal Coordinated Time, international
common time system (formerly GMT, Greenwich Mean Time).
Wave Direction - The direction from
which a wave approaches.
Wave record
- A wave record is a
group of continuous data blocks.
Wave sample
- A single wave height
measurement.
Wind Direction - The direction from
which the wind is blowing.
Zero Crossings
- Number of waves
detected by zero crossing analysis of the demeaned wave elevation record.
Zero Crossing Wave Period
(Tz, Tav) - The average
time interval between similar direction crossings of mean water level for a wave
record. The zero crossing period can also be calculated from the moments of wave
frequency spectra. Tz = square root of(m0/m2), also called
the Mean Spectral Period.
Acknowledgement
Some of the terms and their descriptions in Terminology are
compiled from the publications of UNESCO-ITIC, NOAA and TRANSFER project
deliverable 5.1.