The Modified Mercalli intensity scale measures the effects of an earthquake at a given location. This is in contrast with the seismic magnitude usually reported for an earthquake.
Seismology is the scientific study of earthquakes and the generation and propagation of elastic waves through the Earth or other planetary bodies. It also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, glacial, fluvial, oceanic microseism, atmospheric, and artificial processes such as explosions and human activities. A related field that uses geology to infer information regarding past earthquakes is paleoseismology. A recording of Earth motion as a function of time, created by a seismograph is called a seismogram. A seismologist is a scientist working in basic or applied seismology.
Seismic moment is a quantity used by seismologists to measure the size of an earthquake. The scalar seismic moment is defined by the equation , where
Bruce Alan Bolt was an Australian-born American seismologist and a professor of earth and planetary science at the University of California, Berkeley. Professor Bolt was known as a pioneer of engineering seismology. He served for 15 years on the California Seismic Safety Commission leading public debate on earthquake safety in that state, and acted as a consultant on major projects throughout the world. As well, Bolt published a number of popular and technical books on seismology.
Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. Magnitudes are usually determined from measurements of an earthquake's seismic waves as recorded on a seismogram. Magnitude scales vary on what aspect of the seismic waves are measured and how they are measured. Different magnitude scales are necessary because of differences in earthquakes, the information available, and the purposes for which the magnitudes are used.
The 1891 Mino–Owari earthquake struck the Japanese provinces of Mino and Owari in the Nōbi Plain in the early morning of October 28 with a surface wave magnitude of 8.0 and moment magnitude of 7.5. The event, also referred to as the Nōbi earthquake, the Great Gifu earthquake, or the Great Nōbi earthquake, is the largest known inland earthquake to have occurred in the Japanese archipelago.
The 1999 Athens earthquake occurred on September 7 at near Mount Parnitha in Greece with a moment magnitude of 6.0 and a maximum Mercalli intensity of IX (Violent). The proximity to the Athens metropolitan area resulted in widespread structural damage, mainly to the nearby suburban towns of Ano Liosia, Acharnes, Fyli, Thrakomakedones, Kifissia, Metamorfosi, Kamatero and Nea Filadelfeia. More than 100 buildings across those areas collapsed trapping scores of victims under their rubble while dozens more were severely damaged. With damage estimated at $3–4.2 billion, 143 people were killed, and up to 1,600 were treated for injuries in Greece's deadliest natural disaster in almost half a century.
Body-waves consist of P-waves that are the first to arrive, or S-waves, or reflections of either. Body-waves travel through rock directly.
The Richter scale, also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale, is a measure of the strength of earthquakes, developed by Charles Francis Richter and presented in his landmark 1935 paper, where he called it the "magnitude scale". This was later revised and renamed the local magnitude scale, denoted as ML or ML .
This list of 20th-century earthquakes is a list of earthquakes of magnitude 6 and above that occurred in the 20th century. Sone smaller events which nevertheless had a significant impact are also included. After 1900 most earthquakes have some degree of instrumental records and this means that the locations and magnitudes are more reliable than for earlier events.
Carl Allin Cornell was an American civil engineer, researcher, and professor who made important contributions to reliability theory and earthquake engineering and, along with Luis Esteva, developed the field of probabilistic seismic hazard analysis by publishing the seminal document of the field in 1968.
The concept of Earthquake Duration Magnitude – originally proposed by E. Bisztricsany in 1958 using surface waves only - is based on the realization that on a recorded earthquake seismogram, the total length of the seismic wavetrain – sometimes referred to as the CODA – reflects its size. Thus larger earthquakes give longer seismograms [as well as stronger seismic waves] than small ones. The seismic wave interval measured on the time axis of an earthquake record - starting with the first seismic wave onset until the wavetrain amplitude diminishes to at least 10% of its maximum recorded value - is referred to as "earthquake duration". It is this concept that Bisztricsany first used to develop his Earthquake Duration Magnitude Scale employing surface wave durations.
The 1981 Playa Azul earthquake occurred on October 24, 1981, at 21:22 local time. It was located near Playa Azul, Michoacán, Mexico. The magnitude of the earthquake was 7.2, or 7.3. Three deaths were reported, two from Michoacán and one from Mexico City. Some buildings were damaged in both Michoacán and Mexico City. A small tsunami was registered in Acapulco with a maximum height of 9 cm.
Harry Oscar Wood (1879–1958) was an American seismologist who made several significant contributions in the field of seismology in the early twentieth-century. Following the 1906 earthquake in San Francisco, California, Wood expanded his background of geology and mineralogy and his career took a change of direction into the field of seismology. In the 1920s he co-developed the torsion seismometer, a device tuned to detect short-period seismic waves that are associated with local earthquakes. In 1931 Wood, along with another seismologist, redeveloped and updated the Mercalli intensity scale, a seismic intensity scale that is still in use as a primary means of rating an earthquake's effects.
The 1914 Senboku earthquake occurred on March 15, 1914, at 04:59 or 05:00 local time according to various sources in northern Japan. The earthquake had a magnitude of 7.0.
The World-Wide Standardized Seismograph Network (WWSSN) – originally the World-Wide Network of Seismograph Stations (WWNSS) – was a global network of about 120 seismograph stations built in the 1960s that generated an unprecedented collection of high quality seismic data. This data enabled seismology to become a quantitative science, elucidated the focal mechanisms of earthquakes and the structure of the Earth's crust, and contributed to the development of plate tectonic theory. The WWSSN is credited with spurring a renaissance in seismological research.
Ernst von Rebeur-Paschwitz was a German astronomer, geophysicist and seismologist. He is best known for the first recording of teleseism with the use of his sensitive self-registering horizontal pendulums in 1889. He proposed to create an international network of seismological stations. His ideas led to the founding of the International Seismological Association.
International Association of Seismology and Physics of the Earth's Interior (IASPEI) is an international organization promoting the study of earthquakes and other seismic sources, the propagation of seismic waves, and the internal structure, properties and processes of the Earth.
The 1858 Prome earthquake occurred on August 24 at 15:38 local time in British Burma. The earthquake occurred with a magnitude of 7.6–8.3 on the moment magnitude scale. It had an epicenter in near the city of Pyay (Prome), Bago. The shock was felt with a maximum Modified Mercalli intensity of XI (Extreme) for about one minute. Severe damage was reported in Bago, and off the coast of Rakhine, an island sunk.
Kate E. Allstadt is a geologist and seismologist employed by the U.S. Geological Survey (USGS) who works out of Golden, Colorado. She is a self-described "present-day geologist" for her interest in connections between geology of the Pacific Northwest and the people in its local communities. She is a published expert on the 2014 Oso landslide.
