SSA 2001 Annual Meeting

Technical sessions:
18-20 April 2001 (Wednesday-Friday)

The program is now available

Added Session Topics:

28 February 2001 Nisqually, Washington Earthquake New

This session, all day Friday, 20 April, will feature posters on the earthquake in Washington State. Conveners are Tom Brocher and Ivan Wong.

Bhuj, India "Republic Day" 2001 Earthquake New

The oral session, on Thursday, 19 April from 6:00-8:00 p.m., will feature invited overview papers on the disastrous 26 January earthquake. There will also be an associated poster session all day Friday, 20 April. Session conveners are William Lettis and Arch Johnston.

Individuals interested in presenting in one of these sessions should contact the appropriate conveners.

Special Session Topics:

Problems in Detection, Location, and Discrimination
Convenors: Bill Walter (LLNL, Livermore, CA 94551, and Craig Schultz (LLNL, Livermore, CA 94551,

Many questions have been raised about the potential ability and limits of seismology to detect, locate, and discriminate underground nuclear tests from other events. This ability is a critical part of verifying a comprehensive nuclear test ban treaty (CTBT) and monitoring for underground nuclear tests in general. One such question is, "What are the limits to our ability to detect, locate, and identify events as the magnitude of a potential explosion decreases?" Answering this question involves the trade-off of many factors such as station noise, propagation characteristics, algorithm performance, scaling between large and small events, and the ability to interpolate or transport information from regions with calibration data to those without it. This session focuses on research addressing fundamental problems in detection, location, and discrimination and their interdependencies. Innovative techniques such as correlation detection, sparse station location, and multivariate regional discrimination methods all show great promise. Correction surfaces, where one calibrates the propagation effects expected from any point on the Earth to the monitoring stations using a priori models, empirical data, or both have also been demonstrated to improve performance greatly. In some instances a dedicated calibration shot or planned source phenomenology experiment may be useful in resolving key problems. We solicit presentations on these or any other aspects of seismic nuclear test monitoring.

Earthquake Nucleation and Earthquake Sequences: Constraints from Seismology and Aseismology
Convenors: Paul Silver (Carnegie Institute of Washington, Washington, DC 20015, and Gregory C. Beroza (Dept. of Geophysics, Stanford, CA 94305,

How earthquakes nucleate and how they interact constitute two basic unsolved problems in the physics of earthquakes that are also central to the question of whether earthquakes are predictable. While seismology has provided some useful insights into these two processes, the slow and possibly episodic deformation leading up to earthquake rupture may have only a weak seismic signature. Aseismology, or the high-resolution strain and geodetic measurements related to earthquake occurrence, has the potential to provide important and complementary constraints on the deformation field related to these processes. Talks in this session will focus on earthquake nucleation and earthquake interaction, with an emphasis on the combined use of seismic and aseismic constraints.

Faulting and Earthquake Hazards in the Cascadia Forearc: New Paradigms
Convenors: Tom Brocher (USGS, Menlo Park, CA 94025, and Ivan Wong (URS Greiner-Woodward Clyde, Oakland, CA 94607,

Recent results obtained from seismic reflection and refraction profiling in SHIPS experiments in Puget Sound, as well as high-resolution elevation (LIDAR) and aeromagnetic data, have greatly facilitated paleoseismic investigations in this region and have led to rapid growth in our understanding of the tectonics and seismic hazards within the Puget Lowland. Seismic Hazards Investigation in Puget Sound (SHIPS) experiments and new mapping of the Quaternary have also provided rich data sets for site response and basin focusing investigations. This session will showcase results from these and similar investigations elsewhere in the Cascadia forearc that collectively are transforming our understanding of the seismic hazard there.

Past and Future Large Earthquakes of the San Francisco Bay Area
Convenors: Michael S. Reichle (CDMG, Sacramento, CA 95814, and David P. Schwartz (USGS, Menlo Park, CA 94025,

The Pacific-North American plate boundary passes through the San Francisco Bay area as a complex sequence of locked and creeping strike-slip faults and surface and blind thrust faults. Large earthquakes have occurred and will again in the future. This session will examine (a) the behavior in time and space of Bay Area faults using new palesoseismic, geodetic, and seismologic observations to model fault behavior and (b) the ground motions associated with future urban earthquakes.

Earthquake Forecast and Hazard Models: Issues and Inputs for the Next Generation
Convenors: Steven N. Ward (Institute of Tectonics, UCSC, Santa Cruz, CA 95064,, and Edward H. Field (USGS, Pasadena, CA, 91106,

Methods and models for forecasting the sizes and likelihood of future earthquakes on a fault or in a region, and the expected ground motions at a site from these events, are in an evolutionary state. Simple models are evolving into those that attempt to incorporate the complex behavior and physical properties of the seismogenic crust with dynamic processes of fault rupture. Temporally and spatially limited data on recurrence intervals, crustal structure, near-surface geology, and uncertainties in attenuation and directivity effects provide significant challenges. This session calls for papers addressing issues and new directions for improving physical and statistical models for earthquake forecasting and hazard analysis.

3D Earth Models at Regional and Global Scales
Convenors: Harold Magistrale (Dept. of Geological Sciences, SDSU, San Diego, CA 92182,, Jeroen Ritsema (Caltech, Pasadena, CA 91125,, and Walter D. Mooney (USGS, Menlo Park, CA 94025,

Seismology has moved into three dimensions at all scales, from regional crustal models, such as for the Los Angeles Basin, to global models of the Earth's interior. 3D seismology will be one of the most important research topics for the next decade and will contribute to a wide range of studies, including seismic source, earthquake ground motion, and Earth structure. This session will provide a forum to discuss the issues of constructing, modifying, and evaluating Earth models with the goal of highlighting the importance of 3D seismology.

Development and Use of Near-real-time Seismological Information
Convenors: Lind S. Gee (Berkeley Seismological Laboratory, Berkeley, CA 94720, and David J. Wald (USGS, Pasadena, CA 91106,

This session will include presentations on current developments in rapid earthquake information, from magnitude and location to the spatial mapping of observed and estimated shaking distribution and loss estimation. Papers from current and potential users describing the way in which this information will be utilized are also encouraged. This session is intended to bring the user community together with the developers.

Paleoseismology for the Planet: Problems and Progress in Quantifying Recurrence on Great Faults of the World
Convenors: Daniela Pantosti (Ist. Nazionale di Geofisica, Rome, Italy, and Lisa B. Grant (UCI, Irvine, CA 92697,

During the past ten years paleoseismic studies have spread worldwide. Paleoseismic data such as fault slip rates, earthquake chronologies, and slip/event measurements quantify the temporal and spatial distribution and magnitude of the surface deformation that is the final product of the cycle of strain accumulation and release. As such, they provide a window into the driving mechanism of the earthquake engine and can be used both to develop and to test models of the earthquake process. This session will present recent research results on recurrence and behavior of major faults around the planet and issues that confront the field.

Stress Triggering: New Insights into Earthquake Mechanics
Convenors: Roland Bürgmann (Dept. of Geology and Geophysics, Berkeley, CA 94720, and Ruth Harris (USGS, Menlo Park, CA 94025,

"Stress triggers" and "stress shadows" are now popular terms often invoked to describe the spatial and temporal relationships between earthquakes, and the relationship between human activity and earthquakes. Even though some calculations such as Coulomb failure stress and rate-and-state formulations are becoming more common, how well do we really understand the mechanics and physics of earthquake-earthquake interactions and human-earthquake interactions? Or, if one thinks that we really do understand the interactions, then what can these relationships tell us about the state of stress in the crust, the exact role of pore fluids in earthquake generation, and other big questions related to earthquake hazard? This session welcomes contributions that discuss new insights into earthquake mechanics based on observations (both field and laboratory) and modeling (elastic, viscoelastic, etc.) of static and dynamic stress changes and of the parameters that are critical for these calculations.

The Rate Debate: Paleoseismic vs. Geodetic Rates and Their Implications for the Earthquake Cycle
Convenors: Steve Wesnousky (University of Nevada, Reno, NV 89557, and Wayne Thatcher (USGS, Menlo Park, CA 94025,

Both high-precision geodetic measurements and careful geological studies can provide estimates of slip rates on active faults. On fault zones where such rates have been estimated they sometimes agree within believed uncertainties (e.g., parts of San Andreas Fault system) and sometimes disagree (e.g., Wasatch Fault zone). Causes of disagreement are uncertain. In this session we invite contributions that provide slip rate estimates made using GPS, paleoseismology, and other geologic methods (e.g., geomorphic studies, surface exposure age dating), particularly in regions where both geologic and geodetic estimates are available and causes of agreement/discrepancy are explored.

Observations and Predictions of Strong Ground Motion Wave Fields in a Heterogeneous Earth
Convenors: Douglas S. Dreger (Berkeley Seismological Laboratory, Berkeley, CA 94720, and Kim B. Olsen (Institute for Crustal Studies, Santa Barbara, CA 93106,

The rapid growth and densification of strong motion networks means that seismograms are being recorded with much increased detail, in particular in the near field of large earthquakes. At the same time, increasing demand on accuracy is being posed on ground-motion models and simulation techniques. This session will focus on the opportunities the new generation of seismic data provides for improving our understanding of source, structure, and site effects in controlling the level and variability of strong ground motion in earthquakes. We invite new studies on the accuracy of ground motion simulations, validated against numerical or analytical solutions, and in particular high-resolution seismic ground-motion records.

New Seismological and Engineering Perspectives from Recent Large Earthquakes
Convenors: Kuo-Fong Ma (Dept. of Geological Sciences, National Central University, Ching-Li, Taiwan, and Mehmet Celebi (USGS, Menlo Park, CA 94025,

The Izmit, Turkey; Chi Chi, Taiwan; and other recent large earthquakes and their aftershocks are notable in that they represent the largest earthquakes to be well recorded by strong-motion instrumentation. Many of these recordings come from the very near field, where the signal from static offsets is clearly visible in the data. This session will cover the implications of these data both for our understanding of the earthquake source process and for the design of earthquake-resistant structures.

Return to 2001 Meeting page


Last Update: 18 July 2001