Skip to main content
USGS - science for a changing world
Advanced Search

Filters: Tags: Earthquakes & Volcanoes (USGS) (X)

248 results (297ms)   

View Results as: JSON ATOM CSV
thumbnail
The National Earthquake Information Center of the US Geological Survey has three main missions. First, the NEIC determines as rapidly and as accurately as possible, the location and size of all destructive earthquakes that occur worldwide. Second, the NEIC collects and provides to scientists and to the public an extensive seismic database that serves as a solid foundation for scientific research. Third, the NEIC pursues an active research program to improve its ability to locate earthquakes and to understand the earthquake mechanism. These efforts are all aimed at mitigating the risks of earthquakes to mankind. -from Authors
thumbnail
This is a description, illustrated with photographs, of the 1986 eruptions of Augustine, Pavlof and Akutan volcanoes. Augustine erupted pyroclastic flows, a large eruptive column, ash, and eventually a dome. Pavlof had an important Strombolian eruption which was one of the biggest in the last 30 years. Akutan had a small eruption at the same time. -A.Scarth
thumbnail
The geophysical instrumentation operated by the U.S Geological Survey and others near Parkfield is designed to monitor ongoing tectonic processes that generate earthquakes and to record the strong shaking that results from larger shocks and its effects. this discussion focuses on the former objectives; the latter is discussed in the next section "Ground Shaking and Engineering Studies on the Parkfield Section of the San Andreas Fault Zone." Because scientists expect the anticipated earthquake to resemble the historic Parkfield earthquakes, and in particular that in 1966, the data from the 1966 shock were used to site instruments for optimun benefit before, during, and after the next shock. the primary feature used...
thumbnail
From the south, snow-covered Mount St. Helens looms proudly under a fleecy halo of clouds, rivaling the majestic beauty of neighboring Mount Rainer, Mount Hood, and Mount Adams. Salmon fishermen dot the shores of lakes and streams in the mountain's shadow, trucks loaded with fresh-cut timber barrel down backroads, and deer peer out from stands of tall fir trees.
thumbnail
In many areas of the world, landslides dams are both interesting natural phenomena and significant hazards. A few of the these natural blockages attain heights that rival or exceed those of the largest manmade dams. A landslide dam in its natural state differs from a constructed embankment dam in that it is composed of a heterogeneous mass of poorly consolidated earth debris and has no channeled spillway or other protected outlet for its impoundment. Having no outlet, landslide dams upon overtopping very commonly fail by breaching due to erosion by the overflowing stream. Some of the world's largest and most devastating floods have occurred because of the failure of large landslide dams (Schuster and Costa, 1986)....
thumbnail
Recent earthquakes and a new way of looking at faults suggest that damaging earthquakes are closing in on the San Francisco area. Earthquakes Awareness Week 1989 in northern California started off with a bang on Monday, 3 April, when a magnitude 4.8 earthquake struck 15 kilometers northeast of San Jose. The relatively small shock-its primary damage was the shattering of an air-control tower window-got the immediate attention of three U.S Geological Survey seismologists in Menlo Park near San Francisco. David Oppenheimer, William Bakun, and Allan Lindh had forecast a nearby earthquake in a just completed report, and this, they thought, might be it.
thumbnail
The ninth of January, 1989, was the 32nd anniversary of the great southern California earthquake of 1857. the latest research shows that, on average, at least part of the section of the San Andreas fault that broke then should break again this year. But the same research suggests that the fault's average behavior could be misleading. A newly refined dating of the past 10 San Andreas ruptures adjacent to Los Angeles reveals a previously unrecognized clustering of large earthquakes in bunches of two or three. If this pattern were to hold, Los Angeles would wait at least another 80 years for another jolt from there. But the San Andreas is not that easy to get around.
thumbnail
In the early and middle 1970's, two new space-based geodetic techniques became available that offered unprecedented accuracy in the measurement of distances over long baselines. As described below, Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI) provided a capability to determine in relatively short periods of time the inter-site distance between two observing stations to a level of several centimeters, even if they were separated by thousands or tens of thousands of kilometers. During the 1980's the two techniques have evolved to the point where baselines can now be routinely measured to a level below one centimeter. This is a tenfold improvement in about ten years. Perhaps more important...
thumbnail
Many seismically active regions occur throughout the world as concentrated zones surrounded by the relatively stable crust of shields or platforms. Examples occur in central and eastern North America, northeastern Brazil, Australia, Norway, Svalbard, Greenland, and other places. Some of these zones, such as those at New Madrid, Missouri, and in the St. Lawrence Valley on the Canadian border, extend over relatively large areas and are marked by a high level of seismicity. Others, such as that near Anna Ohio, are smaller, and the level of activity is lower. Some zones are occasinoally sites for major earthquakes which, if they are in populated regions, can cause widespread destrucion and loss of life.
thumbnail
There were two major earthquakes during the last two months of the year, both in the Gulf of Alaska. Earthquake-related deaths were reported from Mexico, Japan and Indonesia. Southern California was hit by two strong earthquakes; both caused damage and some injuries.
thumbnail
In Japan, the level of public awareness of the dangers of earthquakes is high. The 1923 Kanto earthquake killed about 120,000 people out of a total Japanese population of about 50 million; an equivalent disaster in the U.S would involve 600,000 deaths. Today, Japanese society is well aware of the prediction of the Tokai earthquake. It is estimated by the Tokyo earthquake. It is estimated by the Tokyo muncipal government that this predicted earthquake could kill 30,000 people. (this estimate is viewed by many as conservative; other Japanese government agencies have made estimates but they have not been published.) Reduction in the number deaths from 120,000 to 30,000 between the Kanto earthquake and the predicted...
thumbnail
Cooperative research by scientists of the United States and the People's Republic of China (PRC) has resulted in important new finding concerning the fundamental characteristics of earthquakes and new insight into mitigating earthquake hazards. Much of the research is being conducted under the U.S State Department Protocol for Scientific and Technical Cooperation in Earthquake Studies between the PRC State Seismological Bureau (SSB) and the U.S Geological Survey and the National Science Foundation. Activites and prgoress accomplished under the protocol were the subject of two special sessions at the 1985 American Geophyiscal Union Fall Meeting in San Francisco, Calif.
thumbnail
We hate to say that we need a moderate earthquake every once in a while, but experience shows that it surely helps to sell all kinds of seismic safety programs It took the 933 Long Beach earthquake to get the Field Act passed in California requiring the strengthening of our public schools. It took the 197 San Fernando earthquake for Los Angeles to enact a retrofit ordinance requiring reinforcement of demolition of our 8,000 unreinforced masonry buildings, and the 1985 Mexico City earthquake to shorten its compliance period. It took the 1983 Coalinga earthquake to get the State of California to require the identification of unreinforced masonry buildings in risk areas throughout the state.
thumbnail
The Klamath Falls earthquakes of 8:28PM PDT (magnitude 5.9) and 10:45 PM PDT (magnitude 6.0) on September 20, 1993, were felt over an area of about 130,000 sq km in southwestern Oregon and northern California. Losses due to property damage are preliminary estimated to be about 7.5 million. A motorist died when the car he was driving was crushed by a boulder in an earthquake-induced rockfall, and an elderly woman died of a heart attack that was apparently triggered by one of the earthquakes. Most of the damage resulting from the earthquakes was reported from Klamath Falls, approximately 20 km from the source region of earthquakes. As has commonly been the case with earthquakes in other parts of the United States,...
thumbnail
The magnitude 7.1 mainshock on April 25, 992, caused substantial changes in the elevation of the Earth's surface in the Cape Mendocino region. Precise measurements of such elevation changes aid in long-term emergency planning and are needed for engineering design and the maintenance of roads, bridges, and waterways. Such measurements also enable researchers to estimate the attitude and slip of the causative fault. Elevation changes, as well as horizontal displacements of the Earth's surface, are an expected consequence of dip-slip displacement on earthquake faults. the rock surrounding and overlying the fault is forced to stretch and bend to accommodate fault slip. Slip in the case of the April 25 mainshock is...