1993 Okushiri earthquake
UTC time | 1993-07-12 13:17:11 |
---|---|
ISC event | 219326 |
USGS-ANSS | ComCat |
Local date | July 12, 1993 |
Local time | 22:17 |
Magnitude | 7.7 Mw |
Depth | 16.7 km (10.4 mi) |
Epicenter | 42°51′04″N 139°11′49″E / 42.851°N 139.197°E |
Areas affected | Japan, Hokkaido |
Max. intensity | JMA 5[1] VIII (Severe) |
Tsunami | yes |
Casualties | 230 dead |
The 1993 southwest-off Hokkaido earthquake (北海道南西沖地震, Hokkaidō Nansei Oki Jishin) or Okushiri earthquake occurred at 13:17:12
Tectonic setting
The northwestern side of Honshu lies on the southeastern margin of the
This region has been the location for several historical earthquakes, such as the 1964 Niigata and 1983 Sea of Japan earthquakes, with reverse fault mechanisms, on faults trending approximately north–south.
Damage
The earthquake shaking caused moderately severe damage, VIII on the Mercalli scale. The tsunami reached Okushiri between 2 and 7 minutes after the earthquake. A tsunami warning was given 5 minutes after the earthquake by the
The quake caused fires to start in the town of Okushiri, adding greatly to the total damage.Characteristics
Earthquake
The earthquake had two distinct shocks. The first lasted for 20 seconds, while the second lasted 35 seconds.[8]
The rupture occurred on a fault that dipped at 24 degrees to the east. It had an estimated length of 150 km with a displacement of 2.5 m. The island of Okushiri subsided by 5–80 cm.[dead link][3]
Tsunami
The resulting tsunami inundated large parts of Okushiri, despite its tsunami defences. Okushiri had been struck by another tsunami 10 years earlier. A maximum run-up of 32 m was recorded on the western part of the island near Monai. A tsunami was widely observed in the Sea of Japan with a run-up of 3.5 m at Akita in northern Honshu, up to 4.0 m in southeastern Russia and up to 2.6 m on the coast of South Korea.[9]
Landslide
The Okushiri-port landslide involved a volume of 1.5 x 105 m3 of rock. The slide failure occurred at the base of a volcanic breccia bed. The slide occurred in two phases that may match the two separate shocks recorded for the earthquake.[8]
Aftermath
The destructive power of this tsunami led to an overhaul of the sea defences on Okushiri involving the construction of tsunami sluices on a river and strengthened embankments. New escape routes were also provided and help was given for households to purchase emergency broadcast receivers.[10]
See also
References
- ^ "M 7.7 - 107 km W of Iwanai, Japan". United States Geological Survey.
- ^ Japan Meteorological Agency officially named this earthquake 平成5年(1993年)北海道南西沖地震 (Heisei 5 nen (1993 nen) Hokkaidō nansei-oki jishin, literally the 1993 Southwest-off Hokkaido Earthquake). 気象庁が命名した気象及び地震火山現象 Archived 2017-10-29 at the Wayback Machine
- ^ a b c NGDC. "Comments for the Significant Earthquake". Retrieved 6 November 2010.
- ISSN 0370-9868.
- ^ Kanamori, H.; Astiz L. (1985). "The 1983 Akita-Oki Earthquake (Mw=7.8) and its Implications for Systematics of Subduction Earthquakes" (PDF). Earthquake Prediction Research. 3: 305–317. Archived from the original (PDF) on 11 December 2013. Retrieved 21 June 2012.
- .
- ^ S2CID 106398949.
- ^ NGDC. "Comments for the Tsunami Event". Retrieved 6 November 2010.
- ^ Nakao, M. "Okushiri Tsunami Generated by southwest-off Hokkaido earthquake". Failure Knowledge Database. Retrieved 6 November 2010.[permanent dead link]
External links
- The International Seismological Centre has a bibliography and/or authoritative data for this event.