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 2006 Kuril Islands earthquake occurred on November 15 at with a magnitude of 8.3 and a maximum Mercalli intensity of VII and a maximum Shindo intensity of JMA 2. This megathrust earthquake was the largest event in the central Kuril Islands since 1915 and generated a small tsunami that affected the northern Japanese coast. The tsunami crossed the Pacific Ocean and damaged the harbor at Crescent City, California. Post-tsunami surveys indicate that the local tsunami in the central Kuril Islands reached runups of 21.9 metres (72 ft) or higher.
The 1938 Banda Sea earthquake occurred on February 2 with an estimated magnitude of 8.5–8.6 on the moment magnitude scale and a Rossi–Forel intensity of VII. This oblique-slip event generated destructive tsunamis of up to 1.5 metres in the Banda Sea region, but there were no deaths.
The 2007 Kuril Islands earthquake occurred east of the Kuril Islands on 13 January at . The shock had a moment magnitude of 8.1 and a maximum Mercalli intensity of VI (Strong). A non-destructive tsunami was generated, with maximum wave amplitudes of 0.32 meters. The earthquake is considered a doublet of the 8.3 magnitude 2006 Kuril Islands earthquake which occurred two months prior on 15 November 2006 approximately 95 km to the southeast.
The 1992 Landers earthquake occurred on Sunday, June 28 with an epicenter near the town of Landers, California, in San Bernardino County. The shock had a moment magnitude of 7.3 and a maximum Mercalli intensity of IX (Violent).
The 1990 Manjil–Rudbar earthquake occurred on Thursday, June 21, 1990 at in northern Iran. The shock had a moment magnitude of 7.4 and a Mercalli Intensity of X (Extreme).
The 1992 Big Bear earthquake occurred at on June 28 in Big Bear Lake, California, with a moment magnitude of 6.5 and a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale. The earthquake occurred at a relatively shallow depth of 5 kilometers (3.1 mi).
The Dasht-e Bayaz and Ferdows earthquakes occurred in Dashte Bayaz, Kakhk and Ferdows, Iran in late August and early September 1968. The mainshock measured 7.4 on the moment magnitude scale and had a maximum perceived intensity of X (Extreme) on the Mercalli intensity scale. Damage was heavy in the affected areas with thousands of lives lost in the first event and many hundreds more in the second strong event.
In the early morning hours of August 16, 1931, a powerful earthquake occurred in West Texas with a maximum Mercalli intensity of VIII (Severe). Estimates of its magnitude range between 5.8–6.4 mb, making it the most powerful earthquake ever recorded in Texas history. Its epicenter was near the town of Valentine, Texas; there, the earthquake caused damage to many homes and buildings. The earthquake may have been caused by movement along oblique-slip faulting in West Texas, the most seismically-active region in the state. Shaking from the earthquake was perceptible within a 400 mi (640 km) radius of the epicenter, affecting four U.S. states and northern Mexico. Several foreshocks and aftershocks accompanied the primary temblor, with the aftershocks continuing until at least November 3, 1931. The main earthquake caused no fatalities, though several people sustained minor injuries; the damage in Valentine amounted to $50,000–$75,000.
This list of 20th-century earthquakes is a global list of notable earthquakes that occurred in the 20th century. 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. To prevent this list becoming unmanageable, only those of magnitude 6 and above are included unless they are notable for some other reason.
On 13 March, the 1992 Erzincan earthquake struck eastern Turkey with a moment magnitude of 6.7 and a maximum Mercalli intensity of VIII (Severe). Originating on the North Anatolian Fault, it rocked the country, leaving at least 498 people dead, roughly 2,000 injured, and an unknown amount missing. Total financial losses were between $13.5 million and $750 million.
The 1872 North Cascades earthquake occurred at in central Washington Territory. A maximum Mercalli intensity of VIII (Severe) was assessed for several locations, though less intense shaking was observed at many other locations in Washington, Oregon, and British Columbia. Some of these intermediate outlying areas reported V (Moderate) to VII shaking, but intensities as high as IV (Light) were reported as far distant as Idaho and Montana. Due to the remote location of the mainshock and a series of strong aftershocks, damage to structures was limited to a few cabins close to the areas of the highest intensity.
The Sagaing Fault is a major fault in Burma, a mainly continental right-lateral transform fault between the Indian Plate and Sunda Plate. It links the divergent boundary in the Andaman Sea with the zone of active continental collision along the Himalayan front. It passes through populated cities of Mandalay, Yamethin, Pyinmana, the capital Naypyidaw, Toungoo and Pegu before dropping off into the Gulf of Martaban, running for a total length of over 1200 kilometers.
The 2011 Fergana Valley earthquake affected Uzbekistan, Kyrgyzstan and Tajikistan at 01:35 local time on 20 July. The dip-slip shock had a moment magnitude of 6.1 and a maximum Mercalli intensity of VIII (Severe). Its epicenter was located just inside Kyrgyzstan's border in the Fergana Valley region. Fourteen were killed and eighty-six were injured.
The 2014 Murmuri earthquake occurred on August 18 in the Zagros Mountains of Iran with a moment magnitude of 6.2 and a maximum Mercalli intensity of VIII (Severe). The thrust earthquake injured 60–330 people and was followed by a number of high intensity aftershocks.
On December 7, 2015, an earthquake measuring 7.2 on the moment magnitude scale struck Tajikistan 105 km (65 mi) west of Murghab at 07:50 UTC at a depth of 26.0 km (16.2 mi). The earthquake was also felt in neighboring Xinjiang in China, India, Afghanistan, Pakistan and Kyrgyzstan.
The 1941 Gloria Fault earthquake occurred at 18:03:57 UTC in the northern Atlantic Ocean on 25 November 1941. It had a magnitude of about 8.0 on the moment magnitude scale and a maximum perceived intensity of IX (Violent) on the Mercalli intensity scale. It was caused by movement on the Gloria Fault, part of the Azores–Gibraltar Transform Fault. It triggered a small tsunami, which was observed at Newlyn, Cornwall.
On November 2 of 1946, west Kyrgyzstan was struck by a magnitude 7.5–7.6 earthquake, the largest in the republic since 1911. The earthquake's hypocenter is probably located beneath the Tian Shan Mountains, near the border with Uzbekistan and north of Namangan.
The second shock in the 1962 Irpinia earthquake sequence was the largest and most destructive in a series of earthquakes in the southern Apennines. It occurred on 21 August at 18:19 CET, measuring 6.15 and assigned a maximum intensity of IX (Violent). It was preceded by an Mw 5.68 foreshock, and followed by a 5.34 aftershock. The earthquakes resulted in nearly 20 fatalities and significant property losses.
The 1997 Bojnurd earthquake occurred on 4 February at 14:07 IRST in Iran. The epicenter of the 6.5 earthquake was in the Kopet Dag mountains of North Khorasan, near the Iran–Turkmenistan border, about 579 km (360 mi) northeast of Tehran. The earthquake is characterized by shallow strike-slip faulting in a zone of active faults. Seismic activity is present as the Kopet Dag is actively accommodating tectonics through faulting. The earthquake left 88 dead, 1,948 injured, and affected 173 villages, including four which were destroyed. Damage also occurred in Shirvan and Bojnord counties. The total cost of damage was estimated to be over US$ 30 million.
