Shane Straw 12/1/11 Final Project Project Question(s): How does the 3D geometry of earthquake positions under the Marianas Trench compare to the 3D geometry of earthquakes under the San Andreas Fault? Can the earthquake positions be correlated with the type of movement associated with these plate boundaries? To answer these two questions, the plate boundaries and earthquakes associated with the boundaries will need to be analyzed in Arc Scene. Arc Scene is the ArcGIS tool for visualizing 3D data. Once the earthquake geometries of both of the plate boundaries have been analyzed, they can be compared to the known movement of the plates to see if any correlations exist. It should be noted, however, that if a correlation is found it does not necessarily mean that the movement of the plates is determining the positions of the earthquakes. Correlation does not equal causation. It would take more advanced techniques to say for certain whether plate movements are responsible for earthquake geometry. The answers to the two main questions will be given in a mostly qualitative form. However, the numerical values for the magnitudes and depths of the earthquakes will be essential for analyzing their geometries. Preprocessing and Processing: A ‘How-To’ Methods Description Before any analysis can be done, however, topography and bathymetry data must be found for the areas surrounding the two plate boundaries. The 3D capabilities of this ETOPO data are very helpful for visualizing the two plate boundaries and their associated earthquakes in Arc Scene. The detailed descriptions of how to find this data and upload it to Arc Scene are listed below. - Bathymetry data for the Mariana Trench o Go to the NOAA National Geophysical Data Center and click on Bathymetry & Global Relief o Create a custom rectangular grid with coordinates at the corners as follows:  Top Latitude: 26° 00’ N  Bottom Latitude: 9° 00’ N  Left Longitude: 134° 22’ E  Right Longitude: 153° 01’ E o Use the ETOPO1 1-Minute global relief database with a 1 minute grid cell size o For the grid format, use the output grid ASCII Raster Format with the ASCII (ARC) Header o After the search is complete, save the compressed file to the project folder on any hard drive o Extract the data into the folderShane Straw 12/1/11 o As stated above, the file is using a .asc file extension: this needs to be converted to a raster  Use the ASCII to Raster tool to convert the file to a raster o The coordinate system of the raster file is undefined, so now define it in WGS84 geographical coordinates using decimal degrees o Now use the Project Raster tool to project the raster file into UTM coordinates (WGS 1984 UTM Zone 55N) o Load the file into a new Arc Scene document and set the base heights  Have it float on a custom surface using itself as the file name o The Marianas Trench should now appear in Arc Scene, but it will appear almost flat due to the large area it covers o Go to scene properties and change the vertical exaggeration to 10  This should make the elevation differences more clear (and later the depths of the earthquakes) - Bathymetry Data for the San Andreas Fault o Go to the NOAA National Geophysical Data Center and click on Bathymetry & Global Relief o Create a custom rectangular grid with coordinates at the corners as follows:  Top Latitude: 42° 15’ N  Bottom Latitude: 29° 40’ N  Left Longitude: 130° 07’ W  Right Longitude: 111° 34’ W o Use the ETOPO1 1-Minute global relief database with a 1 minute grid cell size o For the grid format, use the output grid ASCII Raster Format with the ASCII (ARC) Header o After the search is complete, save the compressed file to the project folder o Extract the data into the folder o As stated above, the file is using a .asc file extension: this needs to be converted to a raster  Use the ASCII to Raster tool to convert the file to a raster o The coordinate system of the raster file is undefined, so now define it in WGS84 geographical coordinates using decimal degrees o Now use the Project Raster tool to project the raster file into UTM coordinates (WGS 1984 UTM Zone 10N) o Now load the file into a new Arc Scene document and set the base heights  Have it float on a custom surface o The San Andreas Fault should now appear in Arc SceneShane Straw 12/1/11 o Go to the scene properties and change the vertical exaggeration to 10  This should make the elevation differences more clear The next step in the process is to find earthquake data for the areas surrounding the two plate boundaries. The detailed process needed to find this data and utilize it in Arc Scene is listed below. - Earthquake Data for the Marianas Trench o Go to the USGS Earthquake Hazards Program page and click on “Search for an Earthquake”  Set the output file type to Spreadsheet Format (comma delimited)  Set the Data Base to USGS/NEIC (PDE) 1973 – 2011 11 28  Do a rectangular area search and enter the same latitude and longitude coordinates as with the bathymetry data  Under the optional parameters, set the minimum magnitude to 5 and the maximum magnitude to 10  Submit the search o Once the search is complete and your data is available, copy all of the information into a Notepad text document o Open Excel and import the notepad text document  Make sure you import it as delimited by commas and make sure that all the columns are marked as general o Open the Arc Scene document with the bathymetry file of the Marianas Trench  Add the excel document as X,Y data  Make sure that Longitude is in the X field and Latitude is in the Y field  Set the Z coordinates to “depth” - It is very important to note that the earthquake depths are in Kilometers o Once the excel coordinates are in Arc Scene, export the layer as a shapefile o Now project the shapefile into the same coordinate system as the bathymetry file o Now that the earthquake points are in Arc Scene, convert them from 2D points to 3D points by using the tool “Feature To 3D By Attribute”  Make sure that in the height field you use the earthquake depths o Once the new layer appears in Arc Scene, double-click on it and go to the Base Heights tab  Under the Elevation from features box, activate the “Use elevation values in the layer’s features” button and type