Thesis Defense - Fall 2008 - Jason Ricketts

Crustal Structure of the Caucasus/Caspian region using gravity and receiver functions

Jason Ricketts
B.S. Candidate
Advisor Dr. Rob Mellors

Friday, December 12th, 2008 CSL 422, 9:20am

ABSTRACT
The area west of the South Caspian basin is an area of complex and uncertain tectonic structure. Thick sediments within the Kura Depression mask the basement and its subsurface geology is poorly constrained. Forward modeling of receiver functions provides initial constrains. However, a good match is sometimes difficult due to the thick sediments. To further constrain the sedimentary thickness, a 2-D gravity profile from EGM2008 is forward modeled using 2 layers over a half-space.
The 2-D profile extends between the two seismic stations BRD and ALI, and the initial model was based on receiver function results. Gravity data was then used to verify these results as well as to provide any additional constrains on the model.
A proposed cross-section shows a depth to basement of 8 km beneath BRD, and a depth of 18 km beneath ALI. Gravity data also suggests that the sediment-basement contact between these two stations is highly irregular. A model where the basement displays an anticinal shape fits the gravity data as well as the receiver functions. Also located to the south of the profile is the Saatly deep well, which reaches a depth of more than 8 km without hitting basement. The westward component of motion of the South Caspian basin relative to the Kura Depression creates E-W shortening in this region, which can be supported by this model.

Thesis Defense - Fall 2008 - Afton Van Zandt

Southern Coyote Creek Fault to Superstition Hills Fault: New Insight to the San Jacinto Fault System

Afton Van Zandt
M.S. Candidate
Advisors Dr. Rob Mellors , Dr. Thomas K. Rockwell, and Dr. Douglas A. Stow

Friday, December 12th, 2008 CSL 422, 10:00am

ABSTRACT
The Superstition Hills fault (SHF) is an active fault in the San Jacinto fault zone that also creeps aseismically. 58 interferograms from ERS-1 and ERS-2 satellite data (descending, track 356, frame 2943) spanning a time period from 1992 to 2000 were analyzed to measure surface deformation along and near the fault. Interferograms were analyzed separately and as a stacked image. Clear signals due to both groundwater extraction and tectonic movement were observed. Fault creep is observed along the Superstition Hills and Elmore Ranch faults. A broad zone of line-of-sight deformation extends from the north end of the Superstition Hills fault to the southernmost Coyote Creek fault. Phase gradient images were useful in identifying faults, and revealed a previously unknown extension of the Coyote Creek fault.
The existence of the fault was confirmed by field measurements, which included both surface mapping and a trench across the fault. The fault exhibited indications of recent motion including both vertical and strike-slip components.
The InSAR data is modeled using a series of finite faults in an elastic half-space. The observed deformation along the Superstition Hills fault and Elmore Ranch fault can be modeled assuming shallow (< 5 km) creep. Various models were tested to explain the pattern of surface deformation between the Superstition Hills and Coyote Creek fault. The preferred model included a northwest trending vertical right-lateral strike-slip fault north of the Elmore Ranch fault.

SEMINAR - Kim Bak Olsen

LA's Future Earthquake

Kim Bak Olsen
Department of Geological Sciences
San Diego State University

Wednesday, December 3rd, 2008