Induced seismicity studies in Soviet Central Asia
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Earthquake Information Bulletin (USGS)↗
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Soviet prediction of a major earthquake
On November 1, 1978, a magnitude 7 earthquake occurred north of the Pamir Mountains near the Tadjiskistan-Kirghizia border, 150 kilometers east of Garm in Soviet Central Asia. Although the earthquake was felt in Tashkent, Dushanbe, and the Fergana Valley, the epicentral area was uninhabited at that time of year, and no damage was reported.
Earthquake Information Bulletin (USGS)↗
Evaluating the intensity of U.S. earthquakes
The intensity scale based on the Modified Mercalli Scale of 1931 (MM scale) measures the effects of seismic shaking. Intensity estimations are often the only representation of the size of an earthquake when small shocks occur in areas far removed from seismograph stations that can record them instrumentally. The impossibility of setting up and maintaining instruments to measure ground motion everywhere that earthquakes occur makes the intensity scale a necessary and useful method to estimate earthquake effects. The effects of seismic shaking are objective. All observers can agree these are real occurences and not subjective speculation. Reliable intensity evaluations are based not on a single factor on any scale but on consistent combinations.
Earthquake Information Bulletin (USGS)↗
Krakatau 1883
This year marks the 100th anniversary of the eruption of Krakatau, perhaps the most famous volcanic event in recorded history. During a 23-hour period on August 26 and 17, 1883, more than 4 cubic miles of volcanic debris exploded upward from Krakatau, resulting in the death of more than 36,000 people and producing catastrophic devastation. The 1883 events at Krakatau caused phenomena that were recorded around the world that lingered for several years after the main eruption.
Earthquake Information Bulletin (USGS)↗
Seismology program; California Division of Mines and Geology
The year 1980 marked the centennial of the California Division of Mines and Geology (CDMG) and a decade of the Division's involvement in seismology. Factors which contributed to the formation of a Seismology Group within CDMG included increased concerns for environmental and earthquake safety, interest in earthquake prediction, the 1971 San Fernando earthquake and the 1973 publication by CDMG of an urban geology master plan for California. Reasons to be concerned about California's earthquake problem are demonstrated by the accompanying table and the figures. Recent seismicity in California, the Southern California uplift reflecting changes in crustal strain, and other possible earthquake precursors have heightened concern among scientific and governmental groups about the possible occurrence of a major damaging earthquake )M>7) in California.
Earthquake Information Bulletin (USGS)↗
Earthquake predictions using seismic velocity ratios
Since the beginning of modern seismology, seismologists have contemplated predicting earthquakes. The usefulness of earthquake predictions to the reduction of human and economic losses and the value of long-range earthquake prediction to planning is obvious. Not as clear are the long-range economic and social impacts of earthquake prediction to a speicifc area. The general consensus of opinion among scientists and government officials, however, is that the quest of earthquake prediction is a worthwhile goal and should be prusued with a sense of urgency.
Earthquake Information Bulletin (USGS)↗
Can animals help to predict earthquakes?
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Earthquake Information Bulletin (USGS)↗
Climbing in the high volcanoes of central Mexico
A chain of volcanoes extends across central Mexico along the 19th parallel, a line just south of Mexico City. The westernmost of these peaks is Nevado de Colima at 4,636 feet above sea level. A subsidiary summit of Nevado de Colima is Volcan de Colima, locally called Fuego (fire) it still emits sulphurous fumes and an occasional plume of smoke since its disastrous eruption in 1941. Parictuin, now dormant, was born in the fall of 1943 when a cornfield suddenly erupted. Within 18 months, the cone grew more than 1,700 feet. Nevado de Toluca is a 15,433-foot volcanic peak south of the city of Toluca. Just southeast of Mexico City are two high volcanoes that are permanently covered by snow: Iztaccihuatl (17,342 fet) and Popocatepetl (17,887 feet) Further east is the third highest mountain in North America: 18,700-foot Citlateptl, or El Pico de Orizaba. North of these high peaks are two volcanoes, 14, 436-foot La Malinche and Cofre de Perote at 14,048 feet. This range of mountains is known variously as the Cordillera de Anahuac, the Sierra Volcanica Transversal, or the Cordillera Neovolcanica.
Central Mexico↗
Geodimeter measurements and the Southern California uplift
Modern surveying instruments, such as geodimeters, are capable of measuring distances in the range of 1 to 30 kilometers with remarkable precision. Indeed, the present limitation upon the precision of measurement is not the resolution of the instruments themselves but rather the uncertainty introduced by variations in the velocity of light in the atmosphere between the two endpoints of the measured distance. This capability in precise distance measurement can be applied to earthquake studies by using repeated distance measurements to determine changes in the distance between monuments located along the major faults. Such measurements have been made along the San Andreas fault since late 1959, and, as a result, a wealth of data on crustal deformation in that area is now available. In fact, geodimeter measurements of this type furnish a more stable measure of secular strain (change in the ratio of length to length) than any continuously recording strain meter. The superiority of the geodimeter measurement stems principally from the long base line measured which averages over local inhomogeneities (cracks and joints in the rock, inclusions, and so forth). This article describes the important features of the measurement technique as well as some results for the region of the southern California uplift.
California↗
The California geodimeter network; measuring movement along the San Andreas Fault
Following the great California earthquake of 1906 H. F. Reid, a contemporary seismologist, proposed the elastic rebound theory which in effect says that earthquake potential arises from the accumulation of elastic strain within the Earth's crust, just as the stretching of a rubberband creates the potential for violent rebound upon rupture. A direct manifestation of this crustal strain accumulation is the change in distance between adjacent points along opposite sides of a fault. In order to measure the rate at which strain is accumulating along California's San Andreas fault, a netwrok of precise survey lines which criss-cross the fault along its entire lenght in the State is periodically resurveyed with very accurate electro-opitcal distance measuring devices called geodimeters.
California↗
Earthquake engineering research program in Chile
Earthquake engineering research in Chile has been carried out for more than 30 years. Systematic research is done at the university of Chile in Santiago. Other universities such as the Catholic University, university of Concepcion, and the Federico Santa Maria Technical University have begun to teach and conduct research in earthquake engineering in recent years. The fields of research at the University of Chile include the following: Theoretical and empirical characterization of strong round motion. Installation of strong-motion accelerographs. Capacity of strong ground motion to produce structural damage. Seismic risk. Seismic behavior of reinforced masonry houses and buildings. Seismic design of high-rise buildings. Soil dynamics with emphasis on soil liquefaction and soil stability.
Earthquake Information Bulletin (USGS)↗
Jack London and the San Francisco earthquake
After it was over, it seemed to many, and especially to eyewitnesses like Jack London, that the earthquake and fire had devastated San Francisco. However people were confident that, like the phoeniz, San Francisco would rise from the ashes and regain her palce as the "Imperial City of the West."
California↗
Some aspects of the early history of seismology
From the earliest times, people have been terrified yet fascinated by the workings of the Earth. Indeed records of earthquakes have been kept in China for over 3000 years and for 1500 years in Japan. because of the interior of the Earth is inaccessible, nothing about it could be known with any certainty. For thousands of years, thinkers and writers could base their conclusions on a limited number of observations, some of which were as follows; the Earth was not stable and sometimes shook violently; the earthquakes produced were more frequent in some localities than in others; they were sometimes accompanied by heavy rumblings, fissures in the ground, changes in the level of the land, and tidal waves. Oftentimes earthquakes were associated with volcanoes or "burning mountains."
Earthquake Information Bulletin (USGS)↗
Alaska seismic studies
Seismic monitoring in Alaska by the U.S Geological Survey consists of a network of 46 stations focused on the following four areas: Yakatut Bay to Prince William Sound, centered on the Yakatage seismic gap. Anchorage, and the surrounding region of rapid growth and development. The active Cook Inlet volcanoes-Iliamna,Redoubt and Spurr. (Two of three stations near Mount Spurr are funded by the State of Alaska as part of their geothermal program.) The region of the proposed Bradely Lake hydroelectric project on the Kenai Peninsula. (The area is monitored by five stations with funds from the Army Corps of Engineers.)
Alaska↗
Earthquake studies on Canada’s west coast; Pacific Geoscience Centre
On a global scale, Canada's west coast lies within the zone of a seismicity that stretches around the Pacific Ocean. In plate tectonic terms, it is dominated by the same right-lateral shearing between the Pacific and American plates that is responsible for the seismicity of California. However, in southern British Columbia the interaction is further complicated. Between the San Andreas fault in California and the Queen Charlotte fault off British Columbia, the Pacific and American plates are separated by the small independent Juan de Fuca plate system. This is spreading away from the Pacific plate and converging with the margin of the Pacific Northwest. The resulting Cascade volcanic chain and its extension into southern British Columbia are the topograhic expression of its subduction.
Pacific coast↗
The Pocatello Valley, Idaho, earthquake
A Richter magnitude 6.3 earthquake occurred at 8:31 p.m mountain daylight time on March 27, 1975, near the Utah-Idaho border in Pocatello Valley. The epicenter of the main shock was located at 42.094 ° N, 112.478° W, and had a focal depth of 5.5 km. This earthquake was the largest in the continental United States since the destructive San Fernando earthquake of February 1971. The main shock was preceded by a magnitude 4.5 foreshock on March 26.
Idaho; Utah↗
Earthquake prediction; new studies yield promising results
On Agust 3, 1973, a small earthquake (magnitude 2.5) occurred near Blue Mountain Lake in the Adirondack region of northern New York State. This seemingly unimportant event was of great significance, however, because it was predicted. Seismologsits at the Lamont-Doherty geologcal Observatory of Columbia University accurately foretold the time, place, and magnitude of the event. Their prediction was based on certain pre-earthquake processes that are best explained by a hypothesis known as "dilatancy," a concept that has injected new life and direction into the science of earthquake prediction. Although much mroe reserach must be accomplished before we can expect to predict potentially damaging earthquakes with any degree of consistency, results such as this indicate that we are on a promising road.
Earthquake Information Bulletin (USGS)↗
The eastern front of the Sierra Nevada; prone to earthquakes and volcanic eruption
On Sunday morning, May 25, 1980, the weather at Mammoth Lakes, Calif., was sunny and brisk. Suddenly, just before 9:33 a.m, the world became a jarring, lurching, unstable place. Along the front of the Sierra Nevada, the muffled thunder of rockfalls and avalanches prolonged the confusion of sound and motion and added the spectacle of large, rising dust clouds. Three geysers, one 30 ft high, suddenly roared into the air at Hot Creek, although none survived more than a few hours. Some new boiling pools appeared, while many existing hot springs and pools became hotter and more active.
California↗