Studying Seismic Activity

California has 200 or more faults capable of producing large earthquakes. Some of the faults are hidden and some visible at the surface. The biggest concentration of faults are in the San Adreas fault zone and the San Jacinto fault zone. Because of California s large amount of Fault lines the United States Geological Survey, the California division of mines and Geology, the California Institute and other agencies have developed the Southern California Earthquake Center and TriNet Seismic network. This organization monitors the earthquake activity. The seismographs are linked to a computer using a mix of GPS and Landlines . The seismography records are sent to a computer within a few minutes. The information is a available to the public via the Internet. Data at this site is saved to a catalog that are searchable by various parameters. After creating the project using ArcView GIS or Arc View 3D analyst, the next step was to determine the project s objective and scope. Once the data was obtained and converted, maps could be created and analysis performed. The projects objective was to ascertain whether there was a pattern to the earthquakes in Southern California. The area chosen stretches approximately 67 miles by 50 miles. The time frames was 6 months. The SCEC Data center Earthquake and Hypocenter and Phase database was queried for data. Available search parameters were data about magnitudes, start and end date, minimum and maximum depths and Longitude and Latitude. A second site from Cal Tech and the USGS was also used. Time measurements from the SCEC site were converted to Pacific standard time for use with Cal Tech/USGS data. Latittude and longitude measurement in degrees from Cal Tech site were converted to decimal degrees. The highway and street data (from arcview) were used. The highways around the area was selected. Data from the internet was used to determine where the faults were located. Using the line tool, as each line was drawn the name of the fault was added to the table. Once the map was completed, a 3d theme could be created. The 3d theme was created to show the depth of the faults (z axis). In order to make a TIN theme the themes from the 1st view was pasted into the 2nd view. A breakline theme was created parallel to and on each side of an observed pattern of earthquakes perpendicular to the San Jacinto fault. Using the earthquake point theme and breakline

theme, an inverse distance weighting contour was created. The contour theme was used to create the TIN theme. The addition of this TIN caused the scene to rotate slowly and then the patterns became evident. There appears to be a pattern of quakes parallel to the San Jose and Cucamunga faults and perpendicular to the San Andreas and San Jacinto faults.

This article was a excellent source to show the capabilities of Arc View GiS and Arc View 3D analyst. It also taught me a lot about all the wonderful uses and purposes for GIS. GIS will be used a lot more for stuff like volcanoes and earthquakes.