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At least 109 records · Page 6Linked to original sources
USGS1988

Forecasting California’s earthquakes

The first official earthquake forecast for California emphasizes the broad extent of the hazard and the uncertainties involved in predicting the next quakes. For the first time, researchers have reached to a consensus on the threat of large earthquakes to California, things look no worse for Los Angles than before. It still has about a 60 percent chance of being shaken by a large earthquake sometime during the next 30 years. But other heavily populated areas of California, such as San Bernardino and the East Bay area of San Francisco, are now getting their fair share of attention. The new consensus also points up the considerable uncertainties invloved in earthquake forecasting.

California↗
USGS1988

What is worse than the “big one”?

The Whittier Narrows California earthquake sequence (local magnitude, Ml=5.9 or 1 October, 1987), which caused over $358 million damage, indicates that assessments of earthquake hazards in Los Angeles metropolitan area may be underestimated. the sequence ruptured a previously unidentified thrust fault that may be part of a large system of thrust faults that extends across the entire east-west length of the northern margin of the Los Angeles basin. Peak horizontal accelerations from the main shock, which were measured at ground level and in structures, were as high as 0.6g (where g is acceleration of gravity at sea level) within 50 kilometers of the epicenter The first thought in the minds of many residents of the city of Whittier when the first shock hit them was "Is this the big one?" the San Andreas' once-in-150-years great shaker? It might as well have been for Whittier, which is 20 kilometers east of downtown Los Angeles. The ground shook harder there this month than it will when the big one does strike the distant San Andreas, which lies 50 kilometers on the other side of the mountains. And this was only a moderate, magnitude 6.1 shock. Earthquake of magnitude 7 and large 30 times more powerful, could rupture faults beneath the feet of Angelenos at any time. The loss of life and destruction could exceed that caused by the big one.

California↗
USGS1989

New fault picture points toward San Francisco Bay area earthquakes

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.

California↗
USGS1989

Notes about the Armenia earthquake, 7 December 1988

The Earth's crust is a jigsaw of rigid plates like huge paving stones. According to the theory of plate tectonics, these lithosphere plates are constantly in motion, slowly realigning themselves with the passage of time. Ninety to niety-five percent of all earthquakes occur where the plates collide with each other. In Armenia, the Arabian plate abuts against the Eurasian (Europe-Asia) plate. As a result, the region has been plagued by sever earthquakes for thousands of years: an earthquake in 893 A.D. took an estimated 20,000 lives; another in 1667 took 80,000 lives. Whenever the plates moving beneath Armenia interlock, pressure builds. The stress increases, the pressure continues to climb and finally there is a fracture-a sudden release of energy we know as an earthquake.

Earthquakes & Volcanoes (USGS)↗
USGS1989

Taking the pulse of the San Andreas Fault

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.

California↗
USGS1989

The Moon; twenty years later

The 20th anniversary of the first landing on the Moon occurred on July 21, 1989. The vast majority of the Moon rocks collected by the Apollo mission astronauts await further study in the continuing effort to unravel the origin and evolution of Earth's nearest neighbor. Not that the 382-kilogram treasure trove of lunar samples has been gathering dust in the Planetary Materials Laboratory at the Johnson Space Center in Houston. It is just that lunar scientists are being very sparing in their use of the rocks.

Earthquakes & Volcanoes (USGS)↗
USGS1989

Triumph of the Voyager mission

It had been a long, productive trip. Launched in 1977, the two Voyager spacecraft had visited three giant planets, a dozen major Moons, three ring systems with thousands of rings composed of a myriad of tiny Moonlets. The spacecraft had returned 5 trillion bits of data and over 100,000 photographs. The last encounter in our Solar System by Voyager 2 with Neptune was to be a spectacular finale to the 12-year drama.

Earthquakes & Volcanoes (USGS)↗
USGS1986

Volcanoes and atmospheres; catastrophic influences on the planets

For a rare and brief instant in geologic time, we can imagine that the sulfurous, chromatic surface of Io (one of the satellites of Jupiter) lies quiet. Perhaps stars glisten brilliantly through the tenuous nigh sky. Here and there, thick icy fogs enshroud fumaroles where sulfur dioxide leaks from the underworld. Suddenly, a fissure splits the surface and billowing clouds of sulfurous gases and ice hurl orange and black ash into the atmosphere. Minute by minute, the intensity of the eruption builds; stars begin disappearing from the night sky. The rising plume inhales the nearby atmosphere, mixing it with the exhalations from the volcano. Particles of sulfur, sulfur dioxide snow and ash rise to 300 kilometers, later raining down across the planet a thousand kilometers away.

Earthquakes & Volcanoes (USGS)↗
USGS1987

Failure of a massive earthquake-induced landslide dam in Papua New Guinea

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). This article discusses the recent occurrence of a large earthquake-induced landslide that dammed the Bairaman River in the interior of the island of New Britian, Papua New Guinea, and the subsequent overtopping and failure of this landslide dam.

New Britain↗
USGS1990

Intermediate-term earthquake prediction

The problems in predicting earthquakes have been attacked by phenomenological methods from pre-historic times to the present. The associations of presumed precursors with large earthquakes often have been remarked upon. the difficulty in identifying whether such correlations are due to some chance coincidence or are real precursors is that usually one notes the associations only in the relatively short time intervals before the large events. Only rarely, if ever, is notice taken of whether the presumed precursor is to be found in the rather long intervals that follow large earthquakes, or in fact is absent in these post-earthquake intervals. If there are enough examples, the presumed correlation fails as a precursor in the former case, while in the latter case the precursor would be verified. Unfortunately, the observer is usually not concerned with the 'uniteresting' intervals that have no large earthquakes.

Earthquakes & Volcanoes (USGS)↗
USGS1992

The October 1992 Parkfield, California, earthquake prediction

A magnitude 4.7 earthquake occurred near Parkfield, California, on October 20, 992, at 05:28 UTC (October 19 at 10:28 p.m. local or Pacific Daylight Time).This moderate shock, interpreted as the potential foreshock of a damaging earthquake on the San Andreas fault, triggered long-standing federal, state and local government plans to issue a public warning of an imminent magnitude 6 earthquake near Parkfield. Although the predicted earthquake did not take place, sophisticated suites of instruments deployed as part of the Parkfield Earthquake Prediction Experiment recorded valuable data associated with an unusual series of events. this article describes the geological aspects of these events, which occurred near Parkfield in October 1992. The accompnaying article, an edited version of a press conference b Richard Andrews, the Director of the California Office of Emergency Service (OES), describes governmental response to the prediction.

California↗
USGS1991

Seismicity and volcanism; a global perspective

Earthquakes and volcanic eruptions are episodic, related phenomena, resulting from an unstable, evolving Earth. Earthquakes span at least 2 orders of magnitude of energy release (2 of Richter magnitude), and volcanic eruptions at least 3 orders of magnitude in both volume and energy. The largest known earthquakes, of magnitude about 9.5 (as in Chile in 1960), occur somewhere on Earth on average once in less than 100 years. By contrast, the largest volcanic eruptions may exceed 10,00 km 3 in volume, with intervals between them averaging more than 1 million years. The largest documented eruptions have ejected some 3,000 km 3 of material and occur globally on average once in 50,000 to 100,000 years. No known seismic phenomenon has a comparable return interval.

Earthquakes & Volcanoes (USGS)↗
USGS1991

The nature of earthquake prediction

Earthquake prediction is inherently statistical. Although some people continue to think of earthquake prediction as the specification of the time, place, and magnitude of a future earthquake, it has been clear for at least a decade that this is an unrealistic and unreasonable definition. the reality is that earthquake prediction starts from the long-term forecasts of place and magnitude, with very approximate time constraints, and progresses, at least in principle, to a gradual narrowing of the time window as data and understanding permit. Primitive long-term forecasts are clearly possible at this time on a few well-characterized fault systems. Tightly focuses monitoring experiments aimed at short-term prediction are already underway in Parkfield, California, and in the Tokai region in Japan; only time will tell how much progress will be possible.

Earthquakes & Volcanoes (USGS)↗
USGS1990

Volcanology and mineral deposits

Traditionally, volcanologists have focused on forecasting, observing, and interpreting events, processes, and products of eruptions at active volcanoes. Such work involves drama, beauty, fascination scientific problems, and the socially important aim of reducing risks to life and property. In contrast, old volcanic regions, which host many of the world's major hydrothermal-vein, porphyry, and massive-sulfide ore deposits, have been studied mainly by economic geologists, regional stratigraphers, and structural geologists who have limited familiarity with the complexities of volcanic processes. Such "dead" volcanoes, ranging in age from a few million million years (tertiary) to a few billion years (Precambrian), are commonly incompletely and discontinuously preserved due to rapid erosion of originally high-standing volcanic edifices. They can be difficult to date reliably, especially in terms of the time scales of individual volcanic events, and are variably hydrothermally altered-impeding high-resolution petrologic and geochemical studies. Many volcanologists, geochemists, and geophysicists who work on active volcanoes accordingly have been reluctant to become involved in studies of such less tractable rocks.

Earthquakes & Volcanoes (USGS)↗
USGS1987

Devastating tsunami inspires efforts to reduce future tsunami destruction

The beacon from landmark Scotch Cap lighthouse pierced the moonless night of April 1, 1946, in Alaska's remote Aleutain Island chain. In the reinforced concrete lighthouse, five men were engaged in various support operations connected with the maintenance of the 80,000 candlepower beam. Perched atop a building constructed 5 years earlier on a bluff 32 feet above sea level, the proud new light rose a total of 92 feet above the swirling restless seas. On a cliff behind the lighthouse, a second building housed the Coast Guard radio-direction-finding station.

Alaska↗
USGS1988

Volcanoes can generate devastating waves

Explosions. Noxious gases. Lava fountains and flows. Avalanches of superheated pyroclastics. Although volcanic eruptions can cause all these frightening phenomena, it is often the power of the sea that causes many volcano-related deaths. this destruction comes from tsunamis (huge volcano-generated waves) Roughly one-fourth of the deaths occurring during volcanic eruptions have been the result of tsunamis. Moreover a tsunami can transmit the volcano's energy to areas well outside the reach of the eruption itself.

Earthquakes & Volcanoes (USGS)↗
USGS1989

NEIC; the National Earthquake Information Center

Mexico was hit by one of the most devastating earthquakes in its history on September 19, 1985 at 7:18 a.m. MDT time. this earthquake, which was centered about 380 kilometers west-southwest of Mexico City, had a surface-wave magnitude of 8.1. In less than a minute, seismic waves from this earthquake had traveled to Mexico City. At this early hour, people were beginning to get ready for the day's work. Without warning, buildings in some sections of the city began to shake violently. A few minutes later, 412 buildings had collapsed and another 3,124 were badly damaged (figure 1). Most communication systems linking Mexico City to the rest of the world were damaged or rendered inoperable. At least 9,500 people were killed, 30,000 were injured and 100,000 were left homeless by this earthquake. According to some unconfirmed reports, the death toll from this earthquake may have been as high as 35,000. this earthquake is estimated to have seriously affected an area of 825,000 square kilometers, caused between 3 and 4 billion dollars in damage, and been felt by 20 million people.

Earthquakes & Volcanoes (USGS)↗
USGS1992

Correlation between atmospheric precipitation and recent explosions at Mount St. Helens, Washington

Scientists attribute the recent small explosion-like seismic signals at Mount St. Helens to either the geyser-like flashing of superheated groundwater to steam or the release of magmatic gas from the cooling magma system, or both. The contribution of magmaic gas in these events is not currently known. If meteoric water from rain or melting snow is the source, however, we might expect these events to occur most frequently during the rainy season, perhaps even during or immediately following individual storms.

Washington↗