On 16 August 2005, at 11:46:28 JST, a earthquake struck off the coast of the Oshika Peninsula in Miyagi Prefecture, Japan. It injured 100 people and damaged nearly 1,000 homes primarily in the Tōhoku Region.
Tectonic setting The Pacific plate, made of oceanic lithosphere, subducts beneath the Okhotsk Sea plate along a convergent boundary located off the east coast of the northern half of Japan. It runs from the Boso triple junction and ends near Hokkaido, where it joins the Kuril–Kamchatka Trench. At this location, the Pacific plate moves approximately westward relative to the North American plate at a velocity of /yr, subducting beneath Japan at the Japan Trench. This subduction zone is capable of producing megathrust earthquakes with magnitudes greater than 8.5, evident in the historical records. It was on the subduction interface where the 2011 Tōhoku earthquake nucleated. That event involved a rupture by on the subduction zone.
Earthquake Both the United States Geological Survey (USGS) and Japan Meteorological Agency (JMA) recorded a magnitude of and , respectively. Its offshore epicenter was located east of the island of Kinkasan in Miyagi Prefecture. The focal mechanism corresponded to thrust faulting on the Japan Trench. A rupture area of x was estimated, with a maximum slip of west of the epicenter. The observed source time function gives a 20 second duration for the earthquake, with the greatest phase of seismic moment release occurring about five seconds after initiation.
On the Modified Mercalli intensity scale (MMI), a maximum intensity of VII (Very strong) was recorded at Ishinomaki and areas along the Oshika Peninsula, while in Sendai, the MMI reached VI (Strong). A maximum peak ground acceleration of 0.52 g was recorded at Kurihara, Miyagi, while a station at Yamamoto recorded a peak velocity of /s.
By the end of 2005, 19 aftershocks of or higher were recorded by the USGS; the largest aftershock measured , striking on 2 December with an epicenter southeast of the mainshock.
A tsunami advisory was issued by the JMA, but was lifted shortly after. A high tsunami struck the Tōhoku Region's coastline.
+Locations with a seismic intensity of Shindo 5- and higher IntensityPrefectureLocations6-MiyagiKawasaki5+MiyagiSendai, Natori, Higashimatsushima, Ishinomaki, Wakuya, Misato, Ōsaki, Kurihara, TomeFukushimaKunimi, Sōma, Shinchi, MinamisōmaIwateIchinoseki5-MiyagiYamamoto, Kakuda, Watari, Iwanuma, Shibata, Ōsato, Murata, Shiogama, Ōhira, Kami, Minamisanriku, Onagawa FukushimaFukushima City, Nakajima, Tamura, Nihonmatsu, Iitate, Date, KooriIwateRikuzentakata, Hiraizumi, Ōshū, Kanegasaki, Kitakami, Hanamaki, Yahaba, NinoheIbarakiHitachi
Impact At least 100 people were injured, 12 of them seriously, including 79 in Miyagi, 11 in Iwate, 5 in Fukushima, 4 in Saitama and 1 in Yamagata. One house partially collapsed in Saitama, while 984 other households suffered partial damage across Honshu, including 590 in Fukushima, 383 in Miyagi, 9 in Iwate and 2 in Akita.
Some people were injured after the roof of an auditorium collapsed in Sendai. One landslide was also reported at an unspecified location. Bullet trains were suspended, three nuclear power stations were shut down automatically for safety checks, and flights at Haneda Airport in Tokyo were temporarily halted as a precaution. Some 17,000 households were reported to have lost power.
See also List of earthquakes in 2005 List of earthquakes in Japan March 2021 Miyagi earthquake
References
Further reading
External links
Headquarters for Earthquake Research Seismological notes from the Earthquake Research Institute, The University of Tokyo