Geology topics
Publications and source records attributed to H. Spall.
Henry Spall talked recently with Denis Mileti who is in the Department of Sociology, Colorado State University, Fort Collins, Colo. Dr. Mileti is a sociologst involved with research programs that study the socioeconomic impact of earthquake prediction.
In terms of lives lost, rock bursts in underground mines can be as hazardous as earthquakes on the surface. So it is not surprising that fo the last 40 years the U.S Bureau of Mines has been using seismic methods for detecting areas in underground mines where there is a high differential stress which could lead to structural instability of the rock mass being excavated. The microseismic method relies on observational data, amply demonstrated in laboratory experiments, that acoustic noise occurs in rocks subjected to high differential stresses. Acoustic emission becomes most pronounced as the breaking strength of the rock is reached. Laboratory studies have shown that the acoustic emission is linked with the release of stored strain energy as the rock mass undergoes small-scale adjustments such as the formation of cracks. Studies in actual mines have shown that acoustic noises often precede failure of rock masses in rock bursts or in coal bumps. Seismologists are, therefore, very interested in whether these results can be applied to large-scale failures; that is, earthquakes. An active research program in predicting rock bursts in mines is being conducted by Brian T. Brady and his colleagues at the U.S Bureau of Mines, Denver Colo.
Henry Spall talked recently with Robert L. Wesson, the new Chief, Office of Earthquake Studies at the U.S Geological Survey National Center, Reston, Va. Wesson has spent altogether almost 1 year in the U.S.S.R, and 6 months of that time in the Garm area of Soviet Tadzhikistan in 1974.
The Seismological Laboratory at the California Institute of Techonology (Caltech) was founded in 1928 as a result of a study by the Carnegie Institue of Washington. The study was based primarily on a 1916 report by H. O. Wood which recommended that a network of seismic stations be established in southern California. In 1929, the Carnegie Advisory Committee sponsored a conference at Caltech involving world authorities in seismology (fig. 1). Shortly thereafter, Beno Gutenberg was appointed to work at the Seismological Laboratory, although it was not until 1947 that he was formally names as director. He was succeeded in 1957 by Frank Press (now the President's Science Advisor) and in 1967 by Don Anderson. Much of the present research at the laboratory involves disciplines that did not exist 20 years ago. They included studies of the free oscillations of the Earth after a great earthquake, studies of the properties of rocks and minerals at high temperatures and pressures, construction of synthetic seismograms, and planetary seismology. Nevertheless, basic earthquake-related information has always been of consuming interest to the public and the media in this part of California (fig. 2.). So it is not surprising that earthquake prediction continues to be a significant reserach program at the laboratory. Several of the current spectrum of projects related to prediction are discussed below.
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In an article in the last issue of the Earthquake Information Bulletin ("Earthquakes and Plate Tectonics," by Henry Spall), we saw how 90 percent of the world's earthquakes occur at the margins of the Earth's major crustal plates. however, when we look at the distribution of earthquakes in detail, we see that a number of nearly aseismic regions, or seismic gaps, can be found along the present-day plate boundaries. Why is this? And can we regard these areas as being more likely to be the sites for future larger earthquakes than those segments of the plate boundaries that have ruptured recently.
Dr. Gilbert White is Director of the Institute of Behavioral Science at the University of Colorado, Boulder, where he is responsible for natural Hazards Research and Applications Information Center supported by the National Science Foundation. He served in the Executive Office of the president in 1941-42, on the Federal Flood Control Policy Task Force in 1964-65, and on the U.S Geological Survey Advisory Panel on Earthquake Studies. Dr. White has authored five books on the social and economic aspects of natural resources, including water supply and river development, and on floods and other natural hazards.
Dr. Clarence R. Allen is professor of geology and geophysics at the California Institute of Technology. He has been a member of advisory panels to the Executive Office of the President, National Academy of Sciences, National Science Foundation, U.S Geological Survey, UNESCO, California State Mining and Geology Board, and the California Department of Water Resources. Dr. Allen has been President of both the Geological Society of America and the Seismological Society of America (SSA). The title of this interview is based on his presidential address to the SSA in 1976.
Lou Pakiser is Chief of the Branch of Seismicity and Earth Structure of the U.S Geological Survey at Denver, Colo. He is responsible for managing the National Earthquake Information Service (NEIS), the Albuquerque Seismological Laboratory, other U.S Seismic observatories, and a reserach program related to global seismology.
The world's earthquakes are not randomly distributed over the Earth's surface. They tend to be concentrated in narrow zones. Why is this? And why are volcanoes and mountain ranges also found in these zones too? An explanation is to be found in plate tectonics, a concept which has revolutionized thinking in the Earth sciences in the last 10 years. The theory of plate tectonics combines many of the ideas about continental drift (originally proposed in 1912 by Alfred Wegener in Germany) and sea-floor spreading (suggested originally by Harry Hess of Princeton University).
The impressive topographic break at the base of the Wasatch Range immediately east of Salt Lake City, Utah, marks the location where Mormon colonizer Brigham Young said in 1847. "This is the place" Actually, "the place" is termed the Wasatch Front because the Wasatch Range to the east, which rises to heights of 3,600 m, fronts the valleys to the west. The densely settled Wasatch Front area has about 900,000 people, 80 percent of Utah's total population. This population is centered around Salt Lake City, a rapidly growing industrial and tourist center.