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An earthquake is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from those that are so weak that they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. The word tremor is also used for non-earthquake seismic rumbling.
The modified Mercalli intensity scale, developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the effects of an earthquake at a given location, distinguished from the earthquake's inherent force or strength as measured by seismic magnitude scales. While shaking is caused by the seismic energy released by an earthquake, earthquakes differ in how much of their energy is radiated as seismic waves. Deeper earthquakes also have less interaction with the surface, and their energy is spread out across a larger volume. Shaking intensity is localized, generally diminishing with distance from the earthquake's epicenter, but can be amplified in sedimentary basins and certain kinds of unconsolidated soils.
The epicenter, epicentre or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates.
Charles Francis Richter was an American seismologist and physicist.
The moment magnitude scale is a measure of an earthquake's magnitude based on its seismic moment. It was defined in a 1979 paper by Thomas C. Hanks and Hiroo Kanamori. Similar to the local magnitude/Richter scale (ML ) defined by Charles Francis Richter in 1935, it uses a logarithmic scale; small earthquakes have approximately the same magnitudes on both scales. Despite the difference, news media often says "Richter scale" when referring to the moment magnitude scale.
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 1984 Llŷn Peninsula earthquake struck the Llŷn Peninsula in Gwynedd, northwest Wales on Thursday 19 July 1984 at 06:56 UTC. Measuring 5.4 on the Richter scale, it is the largest onshore earthquake to occur in the UK since instrumental measurements began.
Thomas C. Hanks is an American seismologist. He works for the US Geological Survey (USGS) in Menlo Park, California. Dr. Hanks is a member of the Seismological Society of America, the American Geophysical Union, the Earthquake Engineering Research Institute, the Geological Society of America, the Peninsula Geological Society at Stanford, and many related geological societies. Dr. Hanks has authored dozens of scholarly papers in strong-motion seismology and tectonic geomorphology.
The surface wave magnitude scale is one of the magnitude scales used in seismology to describe the size of an earthquake. It is based on measurements of Rayleigh surface waves that travel along the uppermost layers of the Earth. This magnitude scale is related to the local magnitude scale proposed by Charles Francis Richter in 1935, with modifications from both Richter and Beno Gutenberg throughout the 1940s and 1950s. It is currently used in People's Republic of China as a national standard for categorising earthquakes.
The successful development of the local-magnitude scale encouraged Gutenberg and Richter to develop magnitude scales based on teleseismic observations of earthquakes. Two scales were developed, one based on surface waves, , and one on body waves, . Surface waves with a period near 20 s generally produce the largest amplitudes on a standard long-period seismograph, and so the amplitude of these waves is used to determine , using an equation similar to that used for .
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 .
The 2014 Orkney earthquake occurred at 12:22:33 SAST on 5 August, with the epicentre near Orkney, a gold mining town in the Klerksdorp district in the North West province of South Africa. The shock was assigned a magnitude of 5.5 on the Richter scale by the Council for Geoscience (CGS) in South Africa, making it the biggest earthquake in South Africa since the 1969 Tulbagh earthquake, which had a magnitude of 6.3 on the Richter scale. The United States Geological Survey (USGS) estimated a focal depth of 5.0 km (3.1 mi). The CGS reported 84 aftershocks on 5 August and 31 aftershocks on 6 August, with a magnitude of 1.0 to 3.8 on the Richter scale. According to the CGS, the earthquake is the biggest mining-related earthquake in South African history.
Seismic intensity scales categorize the intensity or severity of ground shaking (quaking) at a given location, such as resulting from an earthquake. They are distinguished from seismic magnitude scales, which measure the magnitude or overall strength of an earthquake, which may, or perhaps may not, cause perceptible shaking.
At 23:50 (UTC+8) on 6 February 2018, an earthquake of magnitude 6.4 on the moment magnitude scale hit Taiwan. The epicenter was on the coastline near Hualien, which was the most severely affected area, with a maximum felt intensity of VIII (Severe) on the Mercalli intensity scale. At least 17 deaths were reported, with 285 injured. The maximum foreshock was recorded on 4 February 2018, at 21:56:40. The epicenter was located at Hualien County, Taiwan, reaching a scale of ML 5.8.
On March 3, 2021, 12:16:09 the 2021 Larissa earthquake had a magnitude of 6.3 Mw with an intensity of VIII (Severe) on the Mercalli Scale 9 kilometers west of Týrnavos, Greece. One person was confirmed dead with eleven other people injured. Light shaking was also felt as far as Albania, North Macedonia, Kosovo and Montenegro.
The 2010 Aguas Buenas earthquake, also referred to as the 2010 Christmas Eve earthquake, occurred on December 24 at 7:43 p.m. local time in Aguas Buenas, Puerto Rico. It measured 5.1 on the moment magnitude scale and had a maximum Mercalli intensity of VI (Strong). The event was the largest in Puerto Rico since May 16th of the same year, and the largest to impact the San Juan metropolitan area since 1975. The earthquake was felt throughout the island of Puerto Rico, the island municipalities of Vieques and Culebra, the American and British Virgin Islands, and even in the Dominican Republic across the Mona Passage.
The 2010 Moca earthquake, also referred to as the 2010 Puerto Rico earthquake, occurred on May 16 at 1:16 a.m. local time in Moca, Puerto Rico. The earthquake measured 5.8 on the moment magnitude scale and had a maximum Mercalli intensity of VI (Strong). This was the largest earthquake to strike Puerto Rico since the 1943 Puerto Rico earthquake which measured 7.7 on the Richter scale. This was also the first moderate to major earthquake in recorded history to originate on land in Puerto Rico, as earthquakes in the region usually have their epicenter in the ocean; another earthquake with an epicenter on land would occur later in December of the same year.
On 22 April 2022 at 23:07 local time, a magnitude 5.7 earthquake struck southern Bosnia and Herzegovina. The epicentre was in the Herzegovinian village of Strupići, roughly 10 km (6.2 mi) east of Stolac or 14 km (8.7 mi) from Ljubinje or Nevesinje. It is the country's fifth largest earthquake, as well as its most significant since the 1969 Banja Luka earthquake.
References
- 1 2 3 4 5 6 7 "Të gjitha tërmetet që kanë ndodhur në territorin e Kosovës -". Revista Monitor. September 24, 2019.
- ↑ "USGS Istog earthquake".
- ↑ "2002 Gjilan Earthquake USGS".
- ↑ "An earthquake measuring 5 on the Richter scale rocked..." UPI.
- ↑ "Kopaonik Earthquake USGS".