1994 offshore Sanriku earthquake
UTC time | 1994-12-28 12:19:23 |
---|---|
ISC event | 137333 |
USGS-ANSS | ComCat |
Local date | December 28, 1994 |
Local time | 21:19 |
Magnitude | 7.7 Mw 7.5 MJMA |
Depth | 33 km |
Epicenter | 40°27′04″N 143°29′28″E / 40.451°N 143.491°E |
Areas affected | Japan |
Max. intensity | MMI IX (Violent)[1] JMA 6+ |
Peak acceleration | 0.69 g 673.5 Gal |
Tsunami | 55 cm |
Casualties | 3 killed, 788 injured |
The 1994 offshore Sanriku earthquake (
Geology
The northern part of
In 1999, an investigation was conducted in the source regions of the 1968 offshore Tokachi earthquake and the 1994 offshore Sanriku earthquake. It was found that the structures of crust are heterogeneous in the north and south of 40°10' N. The thickness of the crust is 21 km in the north and 15 km in the south. The P wave velocity in the north is 7% slower than that in the south.[11]
Earthquake
This was an
The slip caused by this earthquake can be divided into a coseismic slip that occurred immediately before, during and immediately after the event, and a long period of slow post-seismic slip that continued for more than a year after the original event. The slow post-seismic slip following this earthquake had a large seismic moment compared with the coseismic slip associated with the main event. The post-seismic slip occurred in two phases; an initial faster short-term phase that lasted for about ten days, terminating with the largest aftershock, followed by a long-term slower phase. The slip area of the initial phase matches the rupture area for the main event. The second phase migrated significantly further down-dip and to the south, along the plate boundary.[7]
The main event released a seismic moment of about 3×1020 Nm, corresponding to magnitude Mw 7.59. However, the total seismic moment released by the main event and the following slow slip events up to about 1 year thereafter was about 8×1020 Nm, which corresponds to magnitude Mw 7.84.[14] The seismic moment of the earthquake was put at 4.3×1020 Nm by the USGS. The slow slip in the landward side of the source region was found to be larger than that in the trenchward side of the source region.[15]
The maximum accelerations recorded in Hachinohe were 602.3 cm/s2 in NS, 488.4 cm/s2 in EW, and 94.1 cm/s2 in UD.[4]
Tsunami
A local tsunami was triggered by this earthquake. The recorded maximum height of the tsunami was in
Aftershocks
The locations of the most part of the aftershocks were within a 170 km × 84 km region west of the initial break of the main shock. Most of the aftershocks occurred in the region of small slip in the main rupture.
The strongest aftershock occurred on January 6, 1995, at 22:37 UTC (January 7, 1995, at 07:37 local time) with magnitude Mw 6.9, leaving 29 people injured. It was located at 40.246 N, 142.175 E with a depth of 27 km. The intensity reached shindo 5 in Hachinohe, Aomori.[18] This aftershock could be felt in Tokyo with shindo 2.
Damage
The felt intensity of the earthquake reached Shindo 6 in Hachinohe and
See also
References
- )
- ^ USGS (5 January 2010). "Significant Earthquakes of the World 1994". Archived from the original on 2011-07-14. Retrieved 13 July 2011.
- ^ a b Disaster Prevention Aomori Prefecture. "Summary of earthquake" (in Japanese). Archived from the original on 2012-01-31. Retrieved 13 July 2011.
- ^ a b "強震波形(三陸沖)" (in Japanese). Archived from the original on 2011-09-28. Retrieved 2011-08-09.
- ^ Sato, Y.; Ichii K.; Miyata M. Morita T. & Iai S (1997). "Strong-motion earthquake records on the 1994 Sanriku-Haruka-Oki earthquake in port areas" (PDF). Technical Note of the Port and Harbour Research Institute, Ministry of Transport, Japan. 892: 5. Archived from the original (PDF) on 26 March 2012. Retrieved 13 July 2011.
- ^ . Retrieved 13 July 2011.
- ^ .
- .
- doi:10.1016/0031-9201(71)90013-6. Archived from the original(PDF) on 2012-03-19. Retrieved 13 July 2011.
- .
- .
- ^ Nishimura, T.; Nakahara H.; Sato H. & Ohtake M. (1996). "Source Process of the 1994 Far East Off Sanriku Earthquake, Japan, as Inferred from a Broad-Band Seismogram" (PDF). Tohoku Geophysical Journal. 34 (4): 121–134. Archived from the original (PDF) on 2012-06-02. Retrieved 13 July 2011.
- ^ Kawasaki, I. "Silent earthquake – what is the origin of slow earthquakes?" (PDF) (in Japanese). Retrieved 13 July 2011.
- ^ Uchida, N.; Igarashi T.; Matsuzawa T. & Hasegawa A. (2002). "Spatio-temporal distribution of afterslip of the 1994 Far-off-Sanriku earthquake, Japan, estimated from repeating earthquake analyses" (PDF). Retrieved 13 July 2011.[permanent dead link]
- ^ "平成6年(1994年)三陸はるか沖地震(1994年12月28日、M7.5)". hp1039.jishin.go.jp (in Japanese).
- ^ NGDC. "Tsunami Event". Retrieved 13 July 2011.
- ^ USGS (5 January 2010). "Significant Earthquakes of the World 1995". Archived from the original on 8 June 2011. Retrieved 13 July 2011.
- ^ "今月の災害・事故 --(平成6年)1994年12月" (in Japanese). Archived from the original on 2011-09-19. Retrieved 2012-03-31.
- ^ a b NGDC. "Comments for the Significant Earthquake". Retrieved 13 July 2011.
- ^ Disaster Prevention Aomori Prefecture. "Summary of damage" (in Japanese). Archived from the original on 2011-03-24. Retrieved 13 July 2011.
External links
- The International Seismological Centre has a bibliography and/or authoritative data for this event.