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At least 325 records · Page 18Linked to original sources
USGS1980

Tremors from earthquakes and blasting in the Powder River basin of Wyoming and Montana

Coal in the Powder River Basin of Wyoming and Montana (fig. 1) is greatly in demand. It can be economically mined from the surface, and the land is much easier to reclaim than land above underground mines that has been damaged by subsidence or by underground fires. Exploitation of the vast coals resources in the basin has caused a rapid influx of population into the area and an associated increase in building construction. The activity has also generated concern about possible regulation of development. With these facts in mind, the U.S Geological Survey has been investigating the geologic implications of development in the Powder River Basin. One area of study has been the effect of earth tremors caused by blasting in the large coal surface mines or by naturally occurring earthquakes. The basin proper was classified by Algermissen and Perkins (1976) as belonging to a region of low seismic risk. Naturally occurring earthquakes are, therefore, mainly of scientific interest, unless of course there was an isolated event that occurred near a populated area or a surface mine. We are not aware of any damage to people or to property caused by blasting in the coal surface mines even though thousands of tons of explosives are detonated each year in the basin. The maximum weight of an individual explosive charge and the time interval between blasts are regulated so that any nearby structures will not be damaged or the residents disturbed. Blasting, nevertheless, does produce seismic tremors that can be recorded over 200 kilometers away. In addition, at one mine, some very low order aftershocks were recorded relatively close to the source within 2 hours after blasting.

Montana; Wyoming↗
USGS1979

Monitoring seismic wave velocities in situ

Beginning in the early 1960's, reports from the Soviet Union described travel-time anomalies of 5 to 20 percent preceding large earthquakes. In the early 970's, similar observations began to be reported outside the U.S.S.R. The most convincing were anomalously low values of the velocity ration, V p /V s , before four earthquakes of magnitudes 2.5 to 3.3 at Blue Mountain Lake, N.Y.; the anomalies were based on large amounts of high-quality data. In Japan, significant decreases were observed in the travel-time ratio, t s /t p , before two thrust-type earthquakes of magnitudes 6. and 5.3. Finally, there is the much discussed report of an anomaly before the magnitude 6.4 San Fernando, Calif., earthquake of 1971 and the implication that the change was caused principally by a decrease in the velocity of the primary (P) wave.

Earthquake Information Bulletin (USGS)↗
USGS1984

Old seismographs still in operation in Northern California

Felt earthquakes are frequent on the Cape Mendocino end of the northern San Andreas fault in Humboldt County, California. For this reason a Bosch-Omori seismograph was installed by Horace Winslow of the U.S Coast and Geodetic Survey in teh old city jail in Ferndale as early as 1932. In 1981 the seismograph was moved to the Ferndale Museum where it is monitored now by James Scalvini. Data from the seismograph are sent to the Survey's National Earthquake Information Service in Golden, Colorado.

Earthquake Information Bulletin (USGS)↗
USGS1982

Progress of the seismological program in El Salvador

El Salvador is located in Central America at the axis of geographical coordinates 14 ° north latitude and 89° west longitude. Situated inside the circumpacific "ring of fire" it is thus vulnerable to sudden earthquakes and volcanic eruptions. Since 1520, El Salvador has sustained approximately 40 destructive earthquakes, an average of one earthquake every 11.4 years. The interval of time between earthquakes during the centuries, however, has been variable. For instance, given the importance of San Salvador as a city since the beginning of the 16th century, it shows historically that over any 100-year interval, there have been four catastrophic earthquakes in the region. During the 20th century, there have been already three large earthquakes in the region. During the 20th century, there have been already three large earthquakes in 1917, 1919, and 1965. If a recurrence of four earthquakes per century is a valid premise, then one may expect another large destructive earthquake before the end of this century. In the following sections, a summary of the seismological programs in El Salvador, their present status, and programs proprosed for the future are discussed.

Earthquake Information Bulletin (USGS)↗
USGS1977

Evolution of Seismic Geyser, Yellowstone National Park

The most significant event that has affected the geyser basins of Yellowstone National Park since its discovery was the Hebgen Lake earthquake, which occurred at 11:37 PM on August 17, 1959, with a Richter magnitude of 7.1. The epicenter of this earthquake was just west of the park, about 48 km northwest of the Upper Geyser Basin. No earthquake of comparable intensity had jarred the geyser basins in historic times. More hydrothermal changes occurred in response to this disturbance than during the previous 90 years of the park's history. During the first few days after the earthquake, a reconnaissance was made of most of the thermal features in the Firehole River geyser basins (fig. 1). Early results showed that at least 289 springs had erupted as geysers, and, of these, 160 were springs with no previous record of eruption (Marler, 1964). Some previously obscure springs had erupted very powerfully, and large pieces of sinter were strewn about their craters.

Wyoming↗
USGS1984

On the front lines in Coalinga

I have often been asked, "As a city manager, what is the first thing you do in an earthquake?" I generally say, "Look up, something heavy might be falling on you. Actually, the first step is to declare an emergency. The city council can ratify it later. The declaration is in your emergency preparedness plan, if you can find it. Mine was under a pile of debris; but after, I turned it up, I located an old declaration from a flood disaster and inserted the word "earthquake" wherever I found the word "flood." The declaration is necessary to give the city some protection from liability, which unfortunately, it will need.

California↗
USGS1976

Monitoring Mount Baker Volcano

Hisotrically active volcanoes in the conterminous United States are restricted to the Cascade Range and extend to the Cascade Range and extend from Mount Baker near the Canadian border to Lassen Peak in northern California. Since 1800 A.D, most eruptive activity has been on a relatively small scale and has not caused loss of life or significant property damage. However, future volcanism predictably will have more serious effects because of greatly increased use of land near volcanoes during the present century. (See "Appraising Volcanic Hazards of the Cascade Range of the Northwestern United States," Earthquake Inf. Bull., Sept.-Oct. 1974.) The recognition an impending eruption is highly important in order to minimize the potential hazard to people and property. Thus, a substantial increase in hydrothermal activity at Mount Baker in March 1975 ( see "Mount Baker Heating Up," July-Aug. 1975 issue) was regarded as a possible first signal that an eruption might occur, and an intensive monitoring program was undertaken.

Washington↗
USGS1979

Electrical measurements as stress-strain monitors

Many of the measurements of phyiscal properties being made in earthquake prediction studies are based on the premise that these properties are influenced by stresses and strains, especially so near the failure point. Electrical properties of rocks are controlled by the fluid in the pores and cracks in the rocks. Because these regions are most influenced by stresses, one should expect electrical measurements to be sensitive measures of changing stresses and strains. Nevertheless, the strain changes we are dealing with are very small, and, consequently, we need very sensitive instruments to detect them.

Earthquake Information Bulletin (USGS)↗
USGS1980

Earthquake hazard hunt

The Earthquake Hazard Hunt should begin at home, with all family members participating. Foresight, imagination, and commonsense are all that are needed as you go from room to room and imagine what would happen when the Earth and house started to shake.

Earthquake Information Bulletin (USGS)↗
USGS1980

Earthquake education in California

In a survey of community response to the earthquake threat in southern California, Ralph Turner and his colleagues in the Department of Sociology at the University of California, Los Angeles, found that the public very definitely wants to be educated about the kinds of problems and hazards they can expect during and after a damaging earthquake; and they also want to know how they can prepare themselves to minimize their vulnerability. Decisionmakers, too, are recognizing this new wave of public concern.

Earthquake Information Bulletin (USGS)↗
USGS1982

Seismology in Mexico

Mexico is situated at the intersection of four major crustal Plates: the Americas Plate, the Pacific Plate, the Caribbean Plate, and the Cocos Plate. The interaction of these four plates is very complex. The pattern of earthquake risk is, therefore, among the most complicated in the world. The average release of seismic energy each is 55x10 21 ergs-more than twice the figure for California.

Earthquake Information Bulletin (USGS)↗
USGS1985

Diversion of lava during the 1983 eruption of Mount Etna

Mankind's first known attempt to divert a lava flow was in 1669, when a flow from Mount Etna volcano threatened the Sicilian city of Catania. This attempt was largely unsuccessful, in part due to opposition by citizens of another town, Paterno. Attempts to divert lava flows from Mauna Loa Volcano on the island of Hawaii by aerial bombing were made in 1935 and 1942, with no signifcant effects. Earthen bariers were hurriedly constructed in attempts to divert flows from Kilauea Volcano, Hawaii in 1955 and 1960, again with little success. The first successful lava diversion took place in 1973, when a thick lava flow was impeded and a harbor saved in Iceland by pumping massive quantities of seawater over advancing aa lava. Nonetheless, methods that could be applied to areas far from sources of water remained unproven. During the 1983 eruption of Etna, Italian scientists managed, for the first time, to convince government authorities that direct intervention in natural volcanic processes was warranted. Both explosives and earthen barriers were used to divert major flows. These efforts were fairly successful, although at the time the historic importance of the operations was not fully recognized.

Mount Etna, Sicily↗
USGS1985

Natural hazards activities of the National Geophysical Data Center

The National Geophysical Data Center (NGDC), a part of the National Oceanic and Atmospheric Administration, has been given the task of collecting, managing, and disseminating the great mass of inofmation produced by scientific observations of the geophysical environment. This article describes NGDC data bases that speifically relate to natural hazards.

Earthquake Information Bulletin (USGS)↗
USGS1984

Jesuits in seismology

Jesuits have been involved with scientific endeavors since the 16th century, although their association with seismology is more recent. What impelled Jesuit priests to also become seismologists is am matter of conjecture. Certainly the migration of missionaries to various parts of the world must have resulted in queries to their fellow Jesuits in Europe. What caused earthquakes? Could they be predicted? Were they connected with the weather? In the 19th and 20th centuries, many Jesuit geophysical stations and obervatories were established in such areas as Cuba, the Philippine Islands, China, Madagascar, Lebanon, Bolivia, Ecuador, Argentina, Colombia, Venezuela, Spain, and Jamaica. Some of these stations are no longer in operation; most have augmented their origional euqipment with instruments of recent design.

Earthquake Information Bulletin (USGS)↗
USGS1980

An economical educational seismic system

There is a considerable interest in seismology from the nonprofessional or amateur standpoint. The operation of a seismic system can be satisfying and educational, especially when you have built and operated the system yourself. A long-period indoor-type sensor and recording system that works extremely well has been developed in the James Madison University Physics Deparment. The system can be built quite economically, and any educational institution that cannot commit themselves to a professional installation need not be without first-hand seismic information. The system design approach has been selected by college students working a project or senior thesis, several elementary and secondary science teachers, as well as the more ambitious tinkerer or hobbyist at home

Earthquake Information Bulletin (USGS)↗
USGS1979

Microearthquake networks and earthquake prediction

A microearthquake network is a group of highly sensitive seismographic stations designed primarily to record local earthquakes of magnitudes less than 3. Depending on the application, a microearthquake network will consist of several stations or as many as a few hundred . They are usually classified as either permanent or temporary. In a permanent network, the seismic signal from each is telemetered to a central recording site to cut down on the operating costs and to allow more efficient and up-to-date processing of the data. However, telemetering can restrict the location sites because of the line-of-site requirement for radio transmission or the need for telephone lines. Temporary networks are designed to be extremely portable and completely self-contained so that they can be very quickly deployed. They are most valuable for recording aftershocks of a major earthquake or for studies in remote areas.

Earthquake Information Bulletin (USGS)↗