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Results for “Earthquake Information Bulletin (USGS)”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 181 records · Page 10Linked to original sources
USGS1978

Water-level monitoring in the area of the Palmdale Uplift, Southern California

Abnormal behavior of water levels in wells has been observed prior to a number of earthquakes. For instance, water-level minima have been noted in the Cienega Winery well before earthquakes on the San Andreas fault. Abnormal water-level fluctuations were used in conjunctions with other precursors to predict the February 4, 1975, Haicheng earthquake in northeastern China. That such changes should occur prior to earthquakes is not surprising. Ground water that occupies the void spaces in porous rocks or alluvium can be expected to rise in wells when an aquifer is squeezed and fall when it is distended. COnfined aquifers, in particualr, have been found to be highly sensitive to Earth strain changes.

California↗
USGS1985

Reducing losses from earthquakes through personal preparedness

Actions to reduce earthquake hazards can be divided into five phases:two occur before the event, one during the event, and two after the event. The phases are: (1) Mitigation techniques taken anywhere from 1 to 20 years before the event, (2) preparedness measures taken 1 to 20 weeks before the event, (3) response during the actual event, (4) recovery operations over 1 to 20 weeks, and (5) reconstruction activities taken from 1 to 20 years. The magnitude of the earthquake and the resources available to communities and individuals will very these times. A prerequisite to personal preparedness is familiarity with and concern about the other hazard-reduction phases. Strengthening the structure of the home, storing water, and showing family members how to shut off utility-supply lines are only a part of personal preparedness. Equally important are other phases such as picking up children from an evacuated school, securing heavy objects at the work palce as well as in the home, and retrofitting the commuter-highway overpasses needed to reunite a family.

Earthquake Information Bulletin (USGS)↗
USGS1978

Radon emanation on the San Andreas Fault

Radon is a radioactive gas with a half-life of 3.8 days. (Half-life is the time required for the substance to lose half of its radioactivity by decay.) It is itself produced by the decay of uranium. Radon is constantly emanated from the Earth into the atmosphere. Many cases are known where anomalously large amounts of radon have been given off along active faults. THe radon emanation has shown variations with time that are related to changing atmospheric conidtions and possibly to nearby seismic activity.

California↗
USGS1984

Stalking the next Parkfield earthquake in Central California

Looking southeast from Middle Mountain toward Gold Hill, it is a subtle furrow in the grassy knolls of the Cholame Valley of California's Coast Range. To geophysicists, this 19-mile section of the San Andreas fault midway between San Francisco and Los Angeles is the most well understood, most intensely monitored fault in the world. As such, it is also the most likely place for American earthquake researchers to become earthquake predictors. The present understanding of the fault has already prompted speculations that the next moderate Parkfield earthquake will strike in early 1988, give or take a few years. Perhaps more importnat, the next rupture of the Parkfield section of the fault could get out of hand and create a much larger earthquake.

California↗
USGS1980

The Southern California uplift revisited

The earthquake that struck Livermore, east of San Francisco, on January 24 was the second moderate earthquake to have occurred in the San Francisco Bay area in 5 months. It raised familiar questions. Does this mean that the "Big One" is coming? Is the theater of heightened concern now in northern California.

California↗
USGS1984

Likelihood of volcanic eruption at Long Valley, California, is reduced

A relatively low level of earthquake activity as well as reduced rates of ground deformation over the past year have led U.S Geological Survey scientists to conclude that the likelihood of imminent volcanic activity at Long Valley, California, is reduced from that of mid-1982 through 1983.

California↗
USGS1983

Seismology in Chile

The Department of Geology and Geophysics, which is under the faculties of Mathematics and Physical Sciences of the University of Chile, is the organization that is responsible for the Seismological Service of Chile and for installing,operating, and maintaining the seismological stations as well as all the strong-motion stations in Chile.

Earthquake Information Bulletin (USGS)↗
USGS1980

The size of earthquakes

How we should measure the size of an earthquake has been historically a very important, as well as a very difficult, seismological problem. For example, figure 1 shows the loss of life caused by earthquakes in recent times and clearly demonstrates that 1976 was the worst year for earthquake casualties in the 20th century. However, the damage caused by an earthquake is due not only to its physical size but also to other factors such as where and when it occurs; thus, figure 1 is not necessarily an accurate measure of the "size" of earthquakes in 1976. the point is that the physical process underlying an earthquake is highly complex; we therefore cannot express every detail of an earthquake by a simple straightforward parameter. Indeed, it would be very convenient if we could find a single number that represents the overall physical size of an earthquake. This was in fact the concept behind the Richter magnitude scale introduced in 1935.

Earthquake Information Bulletin (USGS)↗
USGS1978

Tiltmeter studies in earthquake prediction

Our knowledge is still very limited as to the way in which the Earth's surface deforms around active faults and why it does so. By far the easiest method of providing clues to the mechanisms involved is to record the associated pattern of tilt of the Earth's surface. tilt measurements give us a means of monitoring vertical displacements or local uplift of the crust. The simplest type of tiltmeter is a stationary pendulum (fig. 1). As the Earth's surface distorts locally, the pendulum housing is tilted while, of course, the pendulum continues to hang vertically (that is, in the direction of the gravity vector). The tilt angle is the angle through which the pendulum housing is tilted. The pendulum is the inertial reference (the force of gravity remains unchanged at the site), and tilting of the instrument housing represents the moving reference frame. We note in passing that the tiltmeter could also be used to measure the force of gravity by using the pendulum in the same way as Henry Kater did in his celebrated measurement of g in 1817.

Earthquake Information Bulletin (USGS)↗
USGS1978

Continuous strain measurements near the San Andreas Fault

Changes in the state of stress in the Earth's crust produces corresponding changes in the state of strain and may result, as a consequence, in damaging earthquakes. Monitoring ground strain can, therefore, help us in understanding how stress changes occur and when they are likely to lead to this kind of abrupt release of seismic energy.

California↗
USGS1978

Prediction monitoring and evaluation program; a progress report

Can your friend's relative really predict earthquakes? Or how about that fellow in the mountains who has always liked geology, does he have the answer to the "when" of earthquakes? And if these people do actually predict an earthquake, is it a lucky guess or are they tuned in to something? A lucky guess would be interesting; 1 correct guess in 100 tries is hardly prediction. But 90 out of 100-now that's prediction! As part of an attempt to separate useful predictions from inaccurate guesses, we have kept score on earthquake predictions from all sources brought to our attention over the past year and a half. The program was outlined in "Earthquake Prediction;Fact and Fallacy" by Roger N. Hunter (Earthquake Information Bulletin, vol. 8, no. 5, September-October 1976, p. 24-25). The program attracted a great deal of public attention, and, as a result, our files now contain over 2500 predictions from more than 230 different people.

Earthquake Information Bulletin (USGS)↗
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)↗