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San Jacinto Fault Scanned with a Terrestrial Laser Scanner (TLS)

  • Principal Investigator: Dr. Tom Rockwell (San Diego State University)
  • UNAVCO Engineer: Brendan Hodge
  • Dates: June 2011
  • Location: Clark Lake, San Diego County, USA
  • Funding Source: The National Science Foundation EAR
Written by Brendan Hodge

Overview

Collecting geologic evidence from major pre-historic earthquakes provides clues to Earth's ancient seismic events. One method of data collection is to dissect a portion of ground across a known active fault, and catalogue, measure, and date the sediment left after each earthquake. Dr. Rockwell and his team are searching for the paleoseismic history of the southern San Jacinto Fault, namely the Clark strand. Several trenches have been excavated and may potentially establish the slip rate per event for the past 2-3 earthquakes as well as the earthquake record for the past 1,200 years. Terrestrial Laser Scanner (TLS) equipment was used to scan the fault trench faces and produce a highly detailed image of trench surfaces.


Significance

Geologists are able to better understand the earthquake cycle associated with individual fault strands by determining how often and how strong previous earthquakes were on the fault. An earthquake cycle occurs over many hundreds and thousands of years, but it was only within the last century that modern seismic instruments were developed. So geologist must use preserved evidence in the geologic record to understand the earthquake history of a fault before the advent of modern seismic recordings. The longer we can "look back" into the seismic record of a fault, the more we know about when and how much energy is released on a fault. These types of studies allow us to better predict the seismic hazards associated with a given fault and ultimately provide us with crucial information on the probability of when another earthquake may happen.

About the Terrestrial Laser Scanner (TLS)

The scanner records millions of 3D points by sweeping a laser beam over a scene or object, providing highly accurate, three-dimensional images that can be viewed, navigated, measured and analyzed as 3D models. It is capable of detailed mapping of fault scarps, geologic outcrops, fault-surface roughness, frost polygons, lava lakes, dikes, fissures, glaciers, columnar joints and hillside drainages

Repeat TLS surveys show surface changes through time, so we can measure:

  • changes at the surface of the Earth due earthquakes, landslides, erosion, etc.
  • changes in the shape of a volcano that would affect how it might erupt
  • the speed of ice sheets that drain ice sheets in the polar regions
  • alterations to shorelines due to natural disasters or erosion

To request TLS support for your project, please visit our Project Support Request Form.

Links and Resources


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Last modified Wednesday, 20-Mar-2013 01:47:24 UTC