FREE ESSAY ON SEISMIC ACTIVITY

SEISMIC ACTIVITY

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.