U.S.-U.S.S.R. Joint Meeting on Earthquake Hazards Mitigation: September 9-13, 1991, Moscow, U.S.S.R. (1992)

The working group on seismology and geotechnology discussed possible subjects of cooperative research between the United States and the Soviet Union, related to the problem of earthquake hazard mitigation, and agreed to recommend proposals in the following areas: (A) seismic zonation, (B) microzonation, (C) induced seismicity, and (D) instrumentation. All together, 11 specific proposals were identified in the above four areas. These proposals follow, each with the name(s) of the researcher(s) on the U.S.S.R. side shown in parentheses. The researchers on the U.S. side were not identified here because the present report will most likely be used as a guideline for proposal submission to funding agencies in the United States and the names of researchers cannot be identified beforehand.

In the following, the proposals are described briefly.

(1) Comparison of the state-of-the-art methodologies for seismic zonation between the United States and the Soviet Union by applying them to a common region (Strakhov, Reisner, Garagash). The current state-of-the-art methodologies are different in the two countries because of the difference in availability of data. For example, in general, there are fewer strong-motion data available in the Soviet Union than in the United States. The characterization of earthquake sources in the Soviet Union is close to the eastern United States, where potential faults are not well identified and zonation methods require tectonic models, stress-state calculations, and various geophysical data. There are, however, regions in the Soviet Union, such as the Caucasus, where detailed data similar to California have been accumulated.

It is proposed to choose similar regions in both countries to compare the zonation methodology. Suggested regions are (1) the eastern United States versus most parts of the Soviet Union, (2) California versus the Caucasus, and (3) the Pacific coast of the northwestern United States versus Kamchaka.

(2) Development of methodology for time-dependent seismic hazard analysis (Sobolev). Methods of probabilistic seismic hazard analysis recently developed in the United States by the Electric Power Research Institute, the Lawrence Livermore National Laboratory, and the U.S. Geological Survey (EPRI, LLNL, and USGS) can be adapted to include the earth science information relevant to the time-dependent probability of seismic hazard (long-term earthquake forecast). This type of analysis may be useful to identify, for example, areas in a seismic region that have a low probability of earthquake occurance in the next several decades.

(3) Comparison of the state-of-the-art methodologies for microzonation between the United States and the Soviet Union by applying them to a common area (Osipov, Aljoshin,

Aptikaev). This will include the problems of liquefaction, landslides, and ground motion amplification. Suggested pilot areas are sites covered by loess, which are common in the Soviet Union and can be found in the United States near the New Madrid earthquake epicentral area. The Caucasus and some places in Central Asia are suggested for the study of landslides.

(4) In situ study of nonlinear site amplification at sediment sites using Vibroseis as well as weak and strong-motion data (Nikolayev, Beresnev, Steinberg, Solovjev). This project will have dual approaches. One is to develop a new method for in situ determination of soil properties that are relevant to the non-linear amplification of ground motion. Recent recognition by some U.S. seismologists of the pervasive nonlinear amplification effect on ground at sediment sites and the use of Vibroseis in determining the nonlinearity parameter by some U.S.S.R. seismologists make this proposal a timely one. As was found both in the United States and the Soviet Union, wave velocity changes with stress field changes. The working group proposes to monitor the wave velocity variations in test sites in the United States and the Soviet Union in order to predict their effect on strong motions.

The other approach is to install a seismic array, including downhole seismographs, to collect weak and strong-motion data for delineating the nonlinear effect. We need a site with high probability of strong motion, such as the Caucasus in the Soviet Union or Parkfield in the United States.

A study of the dependence of seismic attenuation on amplitude will also be performed.

(5) Development of observational and theoretical technique for determining the effect of topography and three-dimensional geological structure on strong ground motion (Savich). Suggested pilot study sites include the San Francisco Bay area and valleys in Utah and the Caucasus.

(6) Monitoring potential induced seismicity in the vicinity of the Ragun Dam (Mirzoev). Currently, the Ragun reservoir (planned height of 300 m) is being filled with water. The filling started a year ago and is planned to be completed in nine years. The dam is located within 10 km of an active fault with potential for an earthquake of M=7.5. This area is covered by an existing network, and a complete seismicity catalog has existed since 1955 for M>1.5. The proposed research includes the study of spectral features of micro-earthquakes and requires digital seismographs comparable to the portable seismometer (PASSCAL) instruments. This proposed research has great engineering importance and should be of interest to engineers at the U.S. Bureau of Reclamation and U.S. Army Corps of Engineers.

(7) Laboratory studies on mechanical instability and elastic wave radiation (Sobolev). This proposal will give basic understanding on seismicity induced by various causes.

(8) Induced seismicity by explosions (Nikolayev). This proposal is an outcome of an extensive research program carried out in the Soviet Union on various aspects of nonlinearity in seismic wave generation and propagation. The working group proposes to study the effect of underground nuclear explosions in Nevada and Semipalatinsk test sites on seismicity in respective regions.

(9) In situ studies of rock properties and dynamic processes under seismic vibrations (Nikolayev, Beresnev, Mirzoev). It has been found in the Soviet Union that there is a correlation between the microseisms level change, the water table in wells, and local seismicity. Also, it was found that geochemical, hydrogeological, electrical, and other processes are affected by artificially generated seismic vibrations. The simulation of high-frequency seismic emission was observed as an effect of vibrations. We propose to examine whether similar phenomena exist in southern California where the necessary data are available.

(10) Involvement of U.S. scientists in Tadjikistan’s existing strong-motion program. There exist 35 strong-motion seismographs in Tadjikistan, and there has been a cooperative program between the United States and Tadjikistan since 1975. Currently, however, there is no U.S. scientist involved in the program. We propose to reestablish the U.S. participation.

(11) Installation of strong-motion seismographs in Ragun Dam. There exists a network of strong-motion seismographs in the area surrounding Ragun Dam. There are, however, no seismographs on the dam itself. It is proposed to install strong-motion seismographs on and in the dam for the purpose of studying earthquake-resistant designs of dams.