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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 37 records · Page 2Linked to original sources
USGS1988

State public policy issues involved with the Parkfield prediction experiment.

The earthquake-prediction experiment at Parkfield may well be the most important such experiment currently underway worldwide. Its importance, however, extends beyond the scientific data that will be gathered and whether those data that will be gathered and whether those data can provide reliable prediction methods. Important public policy lessons are being learned (and are yet to be learned), and these lessons may be transferable to other parts of California and the nation. Indeed, the Parkfield experiment has captured the interest of numerous Californians, including State officials, emergency managers, the news media, and at least some of the public.

Earthquakes & Volcanoes (USGS)↗
USGS1988

What was that?

At 4:20 local time on September 19, 1986, Mrs. Laurie Harder saw a meteor passing across the sky above her home in Yellowknife, N.W.T. She reported her observation to Yellowknife Seismic Station staff who examined the records of the Yellowknife seismic array to see if the associated meteoroid had hit Earth and generated observalbe seismic signals.

Yellowknife↗
USGS1988

Geophysical instrumentation near Parkfield

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 for siting was the "1966 rupture zone," which is shown as the orange fault traces on the maps in this section. This zone defines the extent of surface tectonic cracks in 1966 and includes the source areas for fore shocks to the 1934 and 1966 earthquakes (north end of the zone) as well as for apparent precursory fault creep in 1966 (near center of the zone). Scientists believe that if precursors to the next shock are observed, they most likely will be near the 1966 rupture zone.

California↗
USGS1988

History of significant earthquakes in the Parkfield area

Seismicity on the San Andreas fault near Parkfield occurs in a tectonic section that differs markedly from neighboring sections along the San Andreas to the northwest and to the southeast. Northwest of the Parkfield section, small shocks (magnitudes of less than 4) do occur frequently, but San Andreas movement occurs predominantly as aseismic fault creep; shocks of magnitude 6 and larger are unknown, and little, if any, strain is accumulating. In contrast, very few small earthquakes and no aseismic slip have been observed on the adjacent section to the southeast, the Cholame section, which is considered to be locked, in as much as it apparently ruptures exclusively in large earthquakes (magnitudes greater than 7), most recently during the great Fort Tejon earthquake of 1857. The Parkfield section is thus a transition zone between two sections having different modes of fault failure. In fact, the regularity of significant earthquakes at Parkfield since 1857 may be due to the nearly constant slip rate pattern on the adjoining fault sections. Until the magnitude 6.7 Coalinga earthquake on May 2, 1983, 40 kilmoeters northeast of Parkfield, the Parkfield section had been relatively free of stress changes due to nearby shocks; the effect of the Coalinga shock on the timing of the next Parkfield shock is not known.

California↗
USGS1989

Mount St. Helens and Kilauea volcanoes

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.

Mt. St. Helen and Kilauea↗
USGS1991

Natural disasters and insurance and reinsurance

Great natural disasters, that is, those exceeding the economic capacity of the affected region and requiring national or international assistance, have increased dramatically in number and scope over the past few decades. As the accompanying graph shows, on average, from the 1960's to the 1980's there has been a five-fold increase in frequency of natural disasters, an increase in total economic losses by a factor of 3.3 and a rise of total insured losses by a factor of 5.8

Earthquakes & Volcanoes (USGS)↗
USGS1991

On seismological moments and magnitudes

My approach to seismology over the years has always been from the point of view of applied mathematics, as exemplified broadly by the work of the late Sir Harold Jeffreys and Professor K. E. Bullen. Both stresses the development of mathematics in the context of physical systems and of modeling, with an eye always on the side of inference. Seismology provided for them and still provides today the almost perfect paradigm; the problem is the resolution of the detailed consitution of the Earth and its geologically short-term dynamics. The latter part, includes, of course, seismic-risk estimation. The last 20 years have seen the construction of a brilliant theoretical formalism for linear inverse problems in seismology , although, oddly enough, the current popular Earth models do not take account it. It is interesting too that the narrow opinion, prevelent a decade ago, to the effect that the traditional seismic body-wave approaches to structural definition were superceded, has been largely abandoned under today's banner of tomography-as though the Oldham-Jeffreys-Gutenbery inversions were not tomography.

Earthquakes & Volcanoes (USGS)↗
USGS1990

Of parachuting spiders and meat-eating beetles

Scientists have been amazed at the rapid recovery of life that followed the volcanic eruption at Mount St. Helens 10 years ago, but to the uninitiated, the place is still a stark and awesome wasteland. Here and there on the rolling hills of gray volcanic ash around the volcano are clumps of invading fireweed and another pioneer called pearly everlasting. Alder and Willow saplings grow sporadically along the otherwise barren stream courses. Plugs of grass sprout in piles of elk droppings. And deer mic and pocket gophers, the survivialists of the animal world, also have managed to gain foothold.

Washington↗
USGS1990

Will the 1990’s be a decade of increasingly destructive natural disasters?

Today, there is a considerable body of knowledge about natural hazards that laso enables us to devise effective means to limit the damage they cause. Yet, the reality of the situation is that disasters are increasing in number worldwide, and their social and economic impacts are becoming more nad more difficult to hear.

Earthquakes & Volcanoes (USGS)↗
USGS1993

The Klamath Falls, Oregon, earthquakes on September 20, 1993

The strongest earthquake to strike Oregon in more than 50 yrs struck the southern part of the State on September 20, 1993. These shocks, a magnitude 5.9 earthquake at 8:28pm and a magnitude 6.0 earthquake at 10:45pm, were the opening salvo in a swarm of earthquakes that continued for more than three months. During this period, several thousand aftershocks, many strong enough to be felt, were recorded by seismographs. The mainshocks caused light moderate damage at Klamath Falls, a town of about 18,000 residents located only about 20 km east of the epicentral area. Damage included toppled chimneys, cracked masonry, and fallen parapets. Power outages occurred after the strongest shocks. In addition, strong shaking broke water mains, and landslides temporarily blocked highways. the earthquakes also caused two fatalities. A rockfall crushed an automobile, killing a motorist, and an elderly lady had a heart attack. the low population density in the epicentral area- less than five people per sq km- kept the toatl dollar loss to about 7.5 million dollars.

Oregon↗
USGS1990

Geology and land use

Geologists' eyes are trained to find and trace such natural landmarks as flood plains, landslide scars, retreating shoreline bluffs, or surface traces of active earthquake faults. more and more often, in developing areas, we find these obvious signs of trouble being erased by urban development. A geological hazard concealed by landscaping or hosing is fully as dangerous as when it is visible. The geologic limitations for building sites of some areas can be overcome, in part, by skilled engineering and expensive construction practices. But the costs can be prohibitively high, and the solutions are not always completely effective. In "earthquake country," history has shown that costs are highest and risk factors most uncertain in a few easily recognized settings: unstable hill sloped, land at the edge of rapidly eroding sea cliffs, lowlands underlain by saturated estuarine mud of ill, and areas near faults capable of producing magnitude 7 or greater earthquakes. Safety immediately after an earthquake is also a concern in these places, for extreme damage and ground distortion may impede or prevent timely access by emergency equipment.

Earthquakes & Volcanoes (USGS)↗
USGS1992

The ten-year eruption of Kilauea Volcano

The Pu'u 'O' o-Kupaianaha eruption now ranks as the longest-lived historic eruption on the East Rift Zone and the most destructive in Kilauea's recent history. About 1 km 3 of lava erupted during the first 0 years of the eruption. Lava flows have destroyed 181 houses and severed the coastal highway along the volcano's south flank, severely restricting transportation on this part of the island of Hawaii. the eruption consisted of many distinct episodes characterized by activity at different vents and by different eruptive styles. the following summarizes the first 10 years of the eruption, starting with the initial outbreak in 1983.

Hawaii↗
USGS1992

Tectonic framework of the Northern California continental margin

The northern coast of California is one of the most seismically active regions in the continental United States. This activity is largely due to tectonic forces resulting from differing relative motions between three extensive lithospheric plates that meet in this region. These crustal plates are bounded by long fault systems-the Cascadia subduction zone, the San Andreas fault system, and the Mendocino fault- that accommodate these differences in plate motion and that are capable of periodically producing damaging earthquakes. Historic earthquake locations are concentrated in the victinity of the tectonically unstable intersection of these tthree plates and their bounding fault systems.

Oregon; California↗
USGS1991

Volcanic-hazards assessments; past, present, and future

A new reason to study volcanoes has developed within the last few decades; it is to anticipate the specific kinds and extents of future eruptions and their effects on people and property. Such studies are based chiefly on the eruptive histories of volcanoes and the distribution of past eruptive products. Volcanic-hazards studies in the U.S Geological Survey began in the 1960's primarily to provide data useful for hazard mitigation during future eruptions. Worldwide interest in volcanic-hazards assessments was greatly stimulated by the 1980 eruption of Mount St. Helens, just 2 years after a hazards assessment of the volcano was published in U.S Geological Survey Bulletin 1383-C. Many climactic eruption on May 18, although the extent of the unprecedented and devastating lateral blast was not anticipated.

Earthquakes & Volcanoes (USGS)↗