Annual Meeting - SCEC.org

Poster Abstracts
SPACE GEODETIC INVESTIGATION OF INTERSEISMIC DEFORMATION DUE TO THE SAN JACINTO
FAULT NEAR ANZA, CA (B-153)
V. Sahakian, Y. Fialko, Y. Bock, and T. Rockwell
We performed campaign GPS measurements of near-field interseismic deformation in the Anza section of the San Jacinto fault
zone. Our survey occupied 27 benchmarks within 4 km of the fault trace, including a 400-m long alignment array established
across the fault in 1990 by SDSU investigators. To constrain the fault slip rate and locking depth, we used SCEC CMM4
velocities in addition to our near field campaign GPS measurements. We inverted GPS velocities using a non-linear Monte-
Carlo algorithm. The best-fitting slip rate and fault locking depths are 14 ± 2 mm/yr and 16 ± 3 km, respectively. We also
investigated the occurrence of shallow creep on the fault by comparing GPS positions of the alignment array monuments to
the total station measurements conducted in the early 1990’s. This comparison yields a maximum rate of rotation of .002
degrees per year within the array. We combined these observations with simple models of shallow creep to place an upper
bound on the amount of surface creep. The data appear to rule out shallow creep at a rate greater than 0.5 mm/yr. This upper
bound is well below predictions of models of interseismic deformation on rate-and-state faults assuming a two to three
kilometer deep velocity-strengthening layer.
MEDIA TEAM - ABSTRACT (A-159)
A. Sampson, H. Humpleman, and M. Romano
At the University of Southern California, nineteen students from across the nation are brought together to study earthquake
behavior at the Southern California Earthquake Center (SCEC). These students, coming from a wide range of academic
interests, compose the intern class for the Undergraduate Studies in Earthquake Information Technology (UseIT). Each intern
class is presented with a Grand Challenge - a task that can only be completed by combining each interns’ knowledge of
computer science and geology - and it is the Media Team’s responsibility to record this collaboration and development
throughout the entirety of the internship.
In order to accomplish this, the Media Team was in constant dialogue with each of the separate groups working on different
aspects of the Grand Challenge. They collected multiple interviews with interns and supervisors each week and wrote the
voice over narration for the documentary as the interviews were clipped. Shooting footage to be paired with the interviews in
the documentary was a constant process, as was logging and editing the footage filmed. As the Media Team experienced the
internship, they decided UseIT would be best represented by having both a scientific documentary and more light-hearted
intern experience video.
ANALYZING BUILDING RESPONSE THROUGH THE USE OF GPS & STRONG MOTION DATA FOR THE
MONITORING OF INFRASTRUCTURE (A-072)
D. Sanchez, Y. Bock, and D. Melgar
Major earthquakes constantly remind us of the vulnerability of structures to ground vibrations and motion. Accelerometers
are currently being used to collect ground motions in order to estimate displacements of the ground and of structures.
However, this approach has its limitations, providing poor accuracy at low frequencies. With the innovations in GPS sensor
technologies, their contribution in collecting data from earthquakes along with accelerometers has led to obtaining a more
accurate method in estimating ground displacements via a Kalman filter, a signal processing methodology not common in
seismology or earthquake engineering. The advantage of this new methodology is that it takes the strengths of both, seismic
and geodetic networks in order to provide a more precise record of ground motion from an earthquake, resolving the
problems encountered in the low frequencies of the accelerometer data, which are of great interest in tall structures. In this
study, a Kalman filter is being explored using both GPS and accelerometer earthquake engineering data obtained from two
sources: An earthquake simulation testing at UCSD’s Large High-Performance Outdoor Shake Table, which enables us to
compare the results with the true ground-motion that was simulated, ensuring the Kalman filter’s accuracy and data from the
April 2010 Mw 7.2 El Mayor-Cucapah earthquake to test the method in a real world setting. The goal is to investigate these
new displacement records of strong ground motion to determine if a response spectra of higher accuracy can be developed
across a wider range of frequency values and have a better representation of the effects in low frequency building response
due to strong ground motions.
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