WEBINAR - Greg Hirth

Understanding earthquakes at the microscopic scale

David Bowman
Department of Geology and Geophysics
Woods Hole Oceanographic Institution

I will first review of how to relate rock strength determined from lab experiments to geological and geophysical observations - emphasizing apparent paradoxes and successes. I will then introduce why understanding earthquake mechanisms in the oceanic lithosphere can provide new insights into the rheological properties of fault zones, and present an experimental study on fault stability in which analysis of the micromechanics of friction provides justification for the extrapolation of the lab data to natural conditions. With this new insight, I will then return to the problem of relating the lab data to geophysical observations.

New Photos Online - Volcanology - Pinacate

Volcanology - Pinacate

SEMINAR - Greg Hirth

Understanding earthquakes at the microscopic scale

David Bowman
Department of Geology and Geophysics
Woods Hole Oceanographic Institution

March 25th, 2009

I will first review of how to relate rock strength determined from lab experiments to geological and geophysical observations - emphasizing apparent paradoxes and successes. I will then introduce why understanding earthquake mechanisms in the oceanic lithosphere can provide new insights into the rheological properties of fault zones, and present an experimental study on fault stability in which analysis of the micromechanics of friction provides justification for the extrapolation of the lab data to natural conditions. With this new insight, I will then return to the problem of relating the lab data to geophysical observations.

SDSU Science Sampler / San Diego Science Festival

Free Fun Acticities for the Entire Family
MARCH 21st, 12-4pm

SEMINAR - David Bowman

Accelerating Moment Release Before Large Earthquakes: Life and Death of an Earthquake Prediction Scheme

David Bowman
Department of Geological Sciences
California State University, Fullerton

Postponed

It has been suggested that large earthquakes are preceded by a systematic increase in the rate of background seismicity in a broad region around the impending event. This rate change, known as “accelerating moment release” (AMR), has been proposed as a precursory signal that could be used to forecast large earthquakes. Bowman and King [GRL, 2001] demonstrate that the pre-mainshock stress field, as indicated by a simple backslip model of the event, can be used to define the critical region that optimizes the precursory AMR signal. The observation of accelerating seismicity within this region represents a period of increased likelihood of a large earthquake. With sufficient knowledge of the regional tectonics, it should be possible to estimate the likelihood of earthquake rupture scenarios by searching for AMR related to stress accumulation on specific faults. This talk will present two algorithms that randomly search global plate boundaries for AMR signals before potential large events. Each plate boundary is searched for AMR using circular regions following the method of Bowman et al.[1998] and fault-based stress accumulation regions following the approach of Bowman and King [2001]. The fault-based algorithm uses a schematic model of the plate-boundary faults to represent potential sources; subduction zones are modeled as single mega-thrust faults, spreading centers as a normal faults, and transforms as single strike-slip faults. In each approach, the entire global plate boundary network is populated by potential sources and searched for precursory AMR. False-alarm and Failure-to-predict statistics are calculated based on historical seismicity; given the heterogeneity of modern instrumental catalogs, these statistics suggest that the current AMR algorithm does not provide significant predictive power.

The New AGS

AGS (Associated Geology Students) has a new look and a new icon. Check out their new website:
http://www-rohan.sdsu.edu/~ags

Along with their new look AGS has taken on a name from the departments past, Tecton Delvers. The Tecton Delvers was the name of the geology club back in the 1960's.

New AGS Officers:

President: Zachary Hasten
Field of Study: Volcanology
Contact: zhasten1205@gmail.com

Vice President: Evan Martin
Field of Study: Paleontology
Contact: mooseprowler@netscape.net

Secretary: Karl Bloor
Field of Study: Geothermic Processes
Contact: ksbloor@yahoo.com

Treasurer: Heather O'brien
Field of Study: Hydrogeology
Contact: gigglemonsterpi@gmail.com

Representative: Erik Gordon
Field of Study: Hydrogeology
Contact: liljimmy_101@yahoo.com

2009 Alumni Banquet

ANNUAL ALUMNI BANQUET
APRIL 24, 2009

This year's banquet will be held at Tom Ham's Lighthouse on Harbor Island in San Diego. The Friday evening event begins with a social hour at 6pm and dinner at 7pm. The meal will be followed by a program, including a "roast" of this year's recipients of the Baylor Brooks Honored Alumni Award. The two honorees being recognized this year are engineering geologists, Dorian Kuper and Tom Kuper. If you want to contribute a short, silly tale or possibly participate in the roast, let Sue know.

The "Bay Buffet" dinner will include caesar salad, potato salad, fresh seasonal fruit, Tuscan penne pasta, Vercruz mahi mahi, carved turkey, rice, seasonal mixed vegetables and dessert! Beverages will be available for purchase from an in-room, cash bar.

As a fund-raiser to partially fund students' banquet meals and other Alumni Association activities, we will have a silent auction that will be set up at the beginning of the evening and will conclude after the evening's program. If you have any items to donate to the auction, please bring them We sincerely appreciate your donations!

For banquet reservations, please complete and mail in the linked form below by April 17th.

CURRENT SDSU GEO-STUDENTS - At least 50 percent of your banquet fee will be reimbursed IF you make a reservation by the deadline AND show up at the banquet!!! And, remember, SDSU geo-alumni may be your future employers and are a great bunch of people to know! You're gonna be one of them!

Tom Ham’s Lighthouse
2150 Harbor Island Drive
San Diego, CA 92101
619-291-9110
Directions

For More Information :
Contact Sue - 619-442-8022.

Banquet Reservation Form

Gary Girty Awarded the President's Top 25 Award

Thirteen years ago, San Diego State President Stephen L. Weber and his wife Susan began the "Top 25 Awards" at SDSU to celebrate the extraordinary contributions of faculty, staff, students, alumni, and community members.

This year one of the recipients of this prestigious award is Dr. Gary H. Girty from the Department of Geological Sciences. Gary is honored because of his work with the general education course Planet Earth (Geol100). One of his major accomplishments with this blended online/lecture based course is the digital textbook written by Gary. It contains many interactive illustrations, an online syllabus containing specific learning outcomes goals, a set of practice exams (study guides), and video lectures (screencasts) covering material in each of the 13 chapters covered during the semester.

Girty joined the department in 1984. Since then he has supervised the successful completion of 61 M.S. and 79 B.S. theses, and has published 67 papers, books, and guidebooks, and over 76 abstracts the vast majority of them with student co-authors. He was selected for the San Diego State University Senate Excellence In Teaching Award – Recognizing Excellence As A Teacher-Scholar for 2006-2007. In 2002-2003 he was awarded the Outstanding Faculty and Staff Award by the Mortar Board at SDSU, and has been selected as the most influential professor by the department’s top graduating senior 7 times. He has served as the Vice-Chair (2005), Chair (2006), and Past-Chair (2007) of the Cordilleran Section, Geological Society of America. He is currently serving his 9th year as the Chair of the department.

Girty’s research program focuses on (1) understanding how plutonic rock weathers, (2) how fault zone architecture develops, and (2) the tectonic development of the SW Cordillera. Since 2002 he has received a total of $124,281 in external and internal funding, and has published 15 papers in journals and books and 13 abstracts all with student co-authors. He also was one of 6 editors on the GSA Special Paper 347 honoring the career of Gordon Gastil, and was one of 2 editors of the Pacific Section SEPM volume honoring the career of Patrick Abbott.

Thesis Defense Online! - Andrew Gritz

Effect of Heterogeneous Prestress on Near-Field Rupture Directivity

Andrew Gritz
M.S. Candidate
Advisor Dr. Steven Day




ABSTRACT
To supplement the very limited number of strong motion recordings in areas near to earthquake sources, numerical modeling of the rupture process and radiated seismic energy was carried out to study such ground motion. The near fault region is susceptible to very strong shaking both because of proximity to the fault and directivity effects, but may also be sensitive to particulars of the rupture process including effects of heterogeneity on the coherence of the rupture. Stochastic realizations of initial stresses on the fault plane with varying values of roughness, combined with a depth-dependent normal stress, are used in numerical simulations of large strike-slip earthquakes to examine how such heterogeneities influence the near-field directivity effects. The resulting synthetic earthquakes have predominantly unilateral rupture propagation with varying degrees of rupture coherence. Response spectra of the synthetic acceleration records at the free surface are analyzed by a method analogous to that used to develop empirical ground motion relations. The dependence of the response spectral shapes on hypocentral distance reflects, in some cases, a roughly self-similar initial rupture growth. The result is complex behavior of response spectral amplitude as a function of along-strike distance at smaller periods, but clearer directivity (along-strike enhancement) at periods of 2 seconds and above. Also present in many cases is a saturation in the trend of along-strike enhancement of the response spectra values when hypocentral distance exceeds some threshold. At periods of 2 seconds and larger, results of an analysis of directivity match reasonably well with earlier empirical studies, while at a period of 1 second, little directivity is observed, in agreement with recent empirical predictions. The stochastic heterogeneities have mixed effects on directivity, but at larger periods there is systematic increase in directivity effects with increasing roughness. However, more important than this heterogeneity, appears to be the underlying depth dependence of the normal stress. To quantify the observed saturation in directivity effects, data from the simulations is fit to a model capping such effects, and values of the predictor value at which this saturation occurs generally agree with empirical and numerical predictions for large strike-slip faults. The value of the predictor variable at which this saturation occurs, changes when the fault length is extended, and an alternative predictor variable is much better able to track this saturation.

SEMINAR - PetroAzteca

Technical Assessment of the Barents Sea Petroleum Potential

2009 Imperial Barrel Team
John Abeid, Lelsie Clayton,
Bryant Falk, Chris Kohel
and Peter Winther
Department of Geological Sciences
San Diego State University

Wednesday, March 11th, 2009

AAPG’s Imperial Barrel Award Program (IBA) is an annual prospect/exploration evaluation competition/presentation competition between university student teams competing to win scholarship funds dedicated to petroleum geoscience education created for geoscience graduate students. The program is rigorous and contributes to AAPG’s mission of promoting petroleum geoscience training and advancing the careers of geoscience students.

This is a global competition, where the University teams analyze a complete dataset in six to eight weeks prior to the competition and (geology, geophysics, land, economics, production infrastructure, and other relevant materials). Each team delivers their results in a 30-minute presentation to a panel of industry experts.

Students gain experience using real technology on a real dataset. Additionally, students benefit from the feedback from the industry panel, the opportunity to impress potential employers in the audience, and the chance to win cash prizes for their schools, who will select the winning team on the basis of technical quality, clarity and originality.

The IBA is a hands-on opportunity for students to experience the creative process and the high-tech science that is the foundation of the Energy Industry today.

SDSU were the 2008 AAPG Imperial Barrel Pacific Section Champions

New Photos Online - Alumni Field Trip

2009 Annual Alumni Field Trip

The 23rd Annual SDSU Geology Field Trip/Campout was at the Picacho State Recreation Area, California, about 25 miles north of Winterhaven, CA. Jon Sainsbury, who is completing his Master's Thesis in the area, graciously agreed to be the 2009 Field Trip Leader. His work involves mapping an anticlinorium that has been re-activated by strike-slip faulting. By correlating age dates for the Black Mountain Basalt and the Quechan volcanics, which are incorporated into the Bear Canyon conglomerate, evidence for much younger folding than previously interpreted has been inferred. The area also contains the Chocolate Mountains and Gatuna Fault which are detachment faults. These are offset by numerous San Andreas related strike slip faulting in the Eastern California Shear Zone. Some of these faults have displacements of near 0.5 km. These detachment faults separate the Orocopia Shist, a basement gneiss and the Winterhaven Formation.
The Field Trip started from the "Group Campground" at 10:00 AM on Saturday February 28th, 2009.

DIRECTIONS: From SDSU take 1-8 eastbound for 172 miles to the 4th Ave/Winterhaven exit (about 3 hours non-stop for timing purposes.) Make a left turn at the stop sign off the freeway ramp and go about ½ mile to next stop sign. Make right turn onto S-24, cross the canal and in about 300 feet make a left turn staying on S-24. Follow S-24 and the signs towards Picacho SRA. Several miles up the road S-24/Ross Rd. will turn to the right but you will go straight for another 6 miles until the pavement ends. You will follow the main gravel road across the canal and in 18 miles you will reach the campground. Watch for the group camp sign directing you to the left, it is several hundred feet past the park check in stop. GPS coordinates are N 33-01-11.5, W 114-36-58.6. The AAA Colorado River Guide Map (best) and the AAA Imperial County Map (good) both have the roads delineated well for finding the Campground.

Thesis Defense - Spring 2009 - Andrew Gritz

Effect of Heterogeneous Prestress on Near-Field Rupture Directivity

Andrew Gritz
M.S. Candidate
Advisor Dr. Steven Day
Monday, March 9th, 2008 CSL 422, 11:00am

ABSTRACT
To supplement the very limited number of strong motion recordings in areas near to earthquake sources, numerical modeling of the rupture process and radiated seismic energy was carried out to study such ground motion. The near fault region is susceptible to very strong shaking both because of proximity to the fault and directivity effects, but may also be sensitive to particulars of the rupture process including effects of heterogeneity on the coherence of the rupture. Stochastic realizations of initial stresses on the fault plane with varying values of roughness, combined with a depth-dependent normal stress, are used in numerical simulations of large strike-slip earthquakes to examine how such heterogeneities influence the near-field directivity effects. The resulting synthetic earthquakes have predominantly unilateral rupture propagation with varying degrees of rupture coherence. Response spectra of the synthetic acceleration records at the free surface are analyzed by a method analogous to that used to develop empirical ground motion relations. The dependence of the response spectral shapes on hypocentral distance reflects, in some cases, a roughly self-similar initial rupture growth. The result is complex behavior of response spectral amplitude as a function of along-strike distance at smaller periods, but clearer directivity (along-strike enhancement) at periods of 2 seconds and above. Also present in many cases is a saturation in the trend of along-strike enhancement of the response spectra values when hypocentral distance exceeds some threshold. At periods of 2 seconds and larger, results of an analysis of directivity match reasonably well with earlier empirical studies, while at a period of 1 second, little directivity is observed, in agreement with recent empirical predictions. The stochastic heterogeneities have mixed effects on directivity, but at larger periods there is systematic increase in directivity effects with increasing roughness. However, more important than this heterogeneity, appears to be the underlying depth dependence of the normal stress. To quantify the observed saturation in directivity effects, data from the simulations is fit to a model capping such effects, and values of the predictor value at which this saturation occurs generally agree with empirical and numerical predictions for large strike-slip faults. The value of the predictor variable at which this saturation occurs, changes when the fault length is extended, and an alternative predictor variable is much better able to track this saturation.