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At least 361 records · Page 20Linked to original sources
USGS1974

Teleseismic studies indicate existence of deep magma chamber below Yellowstone National Park

The secrets of Yellowstone National Park's spectacular geysers and other hot water and steam phenomena are being explored by the U.S Geological Survey with the aid of distant earthquakes (teleseisms). For some time geologists have known that the remarkable array of steam and hot water displays, for which the park is internationally famous, is associated with intense volcanic activity that occurred in the reigon during the last 2 million years. The most recent volcanic eruption took place about 600,000 years ago creating a large caldera, or crater, 75 kilometers long and 50 kilometers wide. This caldera occupies most of the central part of the present-day park. geologists knew from studies of the surface geology that the volcanic activity which creates the present caldera was caused the present caldera was caused by a large body of magma, a mixture composed of molten rock, hot liquids, and gases, that had forced its way from the deep interior of the Earth into the upper mantle and crust below the Yellowstone area. The dimensions and depth below the surface of this magma body were largely unknown, however, because there was no way to "see" deep below the surface. A tool was needed that would enable earth scientists to look into the curst and upper mantle of the Earth. Such a tool became availabe with the installation by the Geological Survey of a network of seismograph stations in the park.

Yellowstone Park↗
USGS1976

Is there a periodicity in the occurrence of earthquakes?

Various periodicities have been suspected in earthquake activity, but none has yet been proved. In his classic text on seismology, K.E Bullen remarked that small but discernable "trigger" forces, such as tidal effects, temperature changes or barometric changes, have been thought to act as "last straw" phenomena when the earthquake would have occurred anyway.

Earthquake Information Bulletin (USGS)↗
USGS1976

Earthquake prediction; fact and fallacy

Earthquake prediction is a young and growing area in the field of seismology. Only a few years ago, experts in seismology were declaring flatly that it was impossible. Now, some successes have been achieved and more are expected. Within a few years, earthquakes may be predicted as routinely as the weather, and possibly with greater accuracy.

Earthquake Information Bulletin (USGS)↗
USGS1975

Marine terraces; datum planes for study of structural deformation

Along the earthquake-prone coastal area of north-central California, geologists are searching for criteria to establish the nature, extent, and rate of crustal movement or deformation that may be related to activity along known or postulated faults. This search has led to a study of marine terraces along the coast between San Francisco and Santa Cruz in the area that is transected by the Seal Cove-San Gregorio-Palo Colorado fault, a branch of the San Andreas fault system.

Earthquake Information Bulletin (USGS)↗
USGS1980

Children and the San Fernando earthquake

Before dawn, on February 9, 1971, a magnitude 6.4 earthquake occurred in the San Fernando Valley of California. On the following day, theSan Fernando Valley Child Guidance Clinic, through radio and newspapers, offered mental health crises services to children frightened by the earthquake. Response to this invitation was immediate and almost overwhelming. During the first 2 weeks, the Clinic's staff counseled hundreds of children who were experiencing various degrees of anxiety.

Earthquake Information Bulletin (USGS)↗
USGS1985

Kinds of damage that could result from a great earthquake in the central United States

In the winter of 1811-12 a series of three great earthquakes occurred in the New Madrid, Missouri seismic zone in the central United States. In addition to the three principal shocks, at least 15 other earthquakes of intensity VIII or more occurred within a year of the first large earthquake on December 16, 1811. The three main shocks were felt over the entire eastern United States. They were strong enough to cause minor damage cause minor damage as far away as Indiana and Ohio on the north, the Carolinas on the east, and southern Mississippi to the south. They were strong enough to cause severe or structural damage in parts of Missouri, Illinois, Indiana, Kentucky, Tennessee, Mississippi, and Arkansas. A later section in this article describes what happened in the epicentral region. Fortunately, few people lived in the severely shaken area in 1811; that is not the case today. What would happen if a series of earthquakes as large and numerous as the "New Madrid" earthquakes were to occur in the New Madrid seismic zone today? The photographs accompanying this article show some typical structural damage that occurred during various earthquakes in the United States. Structural damage to buildings beings at intensity VIII in the Modified Mercalli intensity scale, a scale used for assigning numbers to earthquake effects. Minor or architectural damage (cracked plaster, windows, and chimneys) occurs at intensities VI and VII, and effects on people and small objects predominate at intensities below VI (earthquake felt, direction and duration noted, dishes broken and so forth). The first four photographs show damage caused by intensity VIII and above. None of the damage shown in the photographs in this report occurred in earthquakes larger than the 1811-12 New Madrid shocks, and most of the examples are from considerably smaller shocks. The first two photos show damage to masonry buildings, mostly old and unreinforced, none designed to be earthquake resistant. How many such buildings are in use in your community? The second pair of photos show damage to modern structures close to the epicenter of a magnitude 6.5 earthquake, a small shock compared to the magnitudes (8.4-8.7) of the New Madrid earthquakes.

Mississippi Valley↗
USGS1977

Remote sensing for lineaments in the Mississippi Embayment

A recurrence of an 1811-12 type earthquake in the Mississippi Valley would pose severe problems to construction in the valley. As William Stauder has stated in the preceding article, a particular difficulty in understanding the seismicity of this area is that, whereas various surface manifestations of the 1811-12 earthquakes have been well documented (for example, sandblows and sunken lands), active fault zones have never been recognized. There may be different reasons for this.

Mississippi embayment↗
USGS1975

The seismic history of the Rio Grande Rift

The Rio Grande Rift, one of the major geologic structures of the Southwest, cuts through the center of New Mexico from north to south. The rift is also referred to as the Rio Grande Trench and as the Rio Grande Trough. It extends from the northern end of the San Luis Valley in Colorado southward 725 kilometres along the course of the Rio Grande River through New Mexico to near El Paso, Tex. The Rio Grande Rift is not a single trough but a series of north-trending basins arranged en echelon and separated by narrow constrictions or channels. The rift follows the western flank of the southern Rocky Mountains and apparently was formed at the same time as the moutains.

Rio Grande↗
USGS1979

Computers at the Albuquerque Seismological Laboratory

The Worldwide Standardized Seismograph Network (WWSSN) is managed by the U.S Geological Survey in Albuquerque, N. Mex. It consists of a global network of seismographs housed in seismic observatories throughout the world. An important recent addition to this network are the Seismic Research Observatories (SRO) which combine a borehole seismometer with a modern digital data recording system.

Earthquake Information Bulletin (USGS)↗
USGS1976

The San Francisco cow; did she or didn’t she?

No one has suggested that Mr. Shafter's nameless cow was the cause of the 1906 earthquake, but she has been the source of as persistent a rumor as Mrs. Murphy's Chicago cow. Since 1906, "the cow that fell in the crack" has been a favorite subject of humorous speculation. large earthquakes have always produced large exaggerations, and, although it is difficult to exaggerate the terror humans feel in an earthquake, many scientists have said that much of what witnesses said they witnessed they did not witness at all. Huge, gaping cracks that legend says open and close in the earth, swallowing whole cities, are among those earthquake features that just aren't featured in earthquakes. True, soil may "snap open and shut," but most earth scientists do not think that the cracks are wide enough or deep enough to accommodate houses.

Earthquake Information Bulletin (USGS)↗
USGS1976

Earthquake watch

When the time comes that earthquakes can be predicted accurately, what shall we do with the knowledge? This was the theme of a November 1975 conference on earthquake warning and response held in San Francisco called by Assistant Secretary of the Interior Jack W. Carlson. Invited were officials of State and local governments from Alaska, California, Hawaii, Idaho, Montana, Nevada, utah, Washington, and Wyoming and representatives of the news media.

Earthquake Information Bulletin (USGS)↗
USGS1976

The sound of an earthquake

Historical accounts of earthquakes often include references to sounds which accompany earthquakes.

Earthquake Information Bulletin (USGS)↗
USGS1974

New cooperative seismograph networks established in southern California

Southern California has more active faults located close to large, urban population centers than any other region in the United States. Reduction of risk to life and property posed by potential earthquakes along these active faults is a primary motivation for a cooperative earthquake research program between the U.S Geological Survey and major universities in Southern California.

California↗
USGS1974

A geologic and geophysical study of the Charleston, South Carolina, earthquake zone

A maximum Modified Mercalli intensity of X was reported in Charleston. Damage to buildings was extensive, railroads were made impassable, and communications were disrupted. During the earthquake 27 people were killed, and 56 later died as a result of exposure and injuries sustained during the shaking. The earthquake was reported felt as far as New England, Wisconsin, and Missouri, an area of 5 million square kilometres.

South Carolina↗