1978 Miyagi earthquake

Coordinates: 38°11′N 142°02′E / 38.19°N 142.03°E / 38.19; 142.03
Source: Wikipedia, the free encyclopedia.

1978 Miyagi earthquake
1978 Miyagi earthquake is located in Tohoku, Japan
1978 Miyagi earthquake
UTC time1978-06-12 08:14:28
ISC event680697
USGS-ANSSComCat
Local date12 June 1978 (1978-06-12)
Local time17:14:28
MagnitudeMs 7.7
Depth44 km (27 mi)
Epicenter38°11′N 142°02′E / 38.19°N 142.03°E / 38.19; 142.03
TypeOblique thrust[1]
Areas affectedJapan, Miyagi Prefecture
Max. intensityJMA 5+

MMI VIII (Severe)
Peak acceleration0.438 g
430 gal[2]
TsunamiYes (minor)
Casualties28 dead, 1,325 injured

The 1978 Miyagi earthquake (1978年宮城県沖地震, 1978 nen Miyagi-ken-oki jishin) occurred at 17:14 local time (08:14 UTC) on 12 June. The epicentre was offshore of

intensity of Shindo 5 in Sendai
and caused 28 deaths and 1,325 injuries.

Geology

The northeastern part of

Okhotsk Plate.[4]

The rupture of the plate interface that caused the earthquake, occurred in two distinct stages, from study of surface and body wave data and the distribution of aftershocks. The first stage of rupture propagated northwards, roughly parallel to the trench axis, along the upper of the two aftershock zones. The second stage began after about 11 seconds with a second shock, about 30 km westward of the first, at the base of the upper aftershock zone, propagating down dip. The cause of this rupture sequence is thought to be the presence of a barrier, a zone of higher strength, between the two aftershock zones.[1]

Earthquakes with similar magnitudes have occurred in this region periodically, about every 40 years. Such earthquakes include the ones that occurred in 1793, 1835, 1861, 1897, 1936, and 1978.

characteristic earthquake.[7]

The rupture zone of the 1978 earthquake occurred at the westernmost limit of known interplate earthquakes, some 150 km back from the trench. This deepest part of the rupture zone, about 40 km, is interpreted to represent the depth of transition to aseismic creep on the plate interface.[4]

The maximum peak ground acceleration recorded was 0.125g.[8]

There was a foreshock of magnitude Mj 5.8 at 17:06 local time, minutes before the main shock.[9]

Damage

There were widespread landslides that caused extensive damage to highways and one death in the area around Sendai.[10] 1,183 houses were completely destroyed within Miyagi Prefecture, with a further 5,574 partially destroyed.[11] Soil liquefaction was observed in lands claimed by embankment.[12] No damage was reported from the tsunami.[13]

Tsunami

A maximum wave height of about 60 cm (24 in) was recorded at

Onagawa, close to the epicenter.[14]

Aftermath

The extent of damage to buildings caused by the earthquake, led directly to a revision of the Japanese Building Standard Act in 1981.[15] The earthquake also led to a major revision in the Earthquake Insurance System, which had been set up by the Japanese government in 1966.[11]

2011 Tōhoku earthquake and tsunami

As of March 2011 it is not known if the 2011 Tōhoku earthquake and tsunami is related to the 1978 Miyagi quake periodic sequence. Some involved geological research will be required to see if there is a relationship between the quake events.

Notable linkages

  • The time difference between the quakes is 33 years – a number that is within the probability for being related to the 1978 Miyagi quake sequence.
  • There are some suggestions that the 2011 Tōhoku quake is part of a 1000-year sequence (that is not related to the 40-year Miyagi quake sequence) as a
    similar quake and tsunami hit the Sendai coast in 869 AD.[16]

See also

References

  1. ^
    doi:10.1016/0031-9201(80)90081-3
    .
  2. ^ Ellingwood, Bruce (1980). "An Investigation of the Miyagi-ken-oki, Japan, Earthquake of June 12, 1978".
  3. ^ USGS. "Significant Earthquakes of the World 1978". Archived from the original on 23 January 2010. Retrieved 6 July 2010.
  4. ^
    hdl:2027.42/95645
    .
  5. ^ "webpage on recurrent earthquakes at Miyagi" (in Japanese). Retrieved 6 July 2010.
  6. ^ "webpage on the 2005 Miyagi earthquake" (in Japanese). Retrieved 6 July 2010.
  7. doi:10.1186/BF03352657
    .
  8. ^ Brady, A. Gerald (1980). An investigation of the Miyagi-ken-oki, Japan, earthquake of June 12, 1978. National Bureau of Standards. p. 123.
  9. ^ "Archived copy" (PDF). Archived from the original (PDF) on 28 August 2020. Retrieved 26 April 2013.{{cite web}}: CS1 maint: archived copy as title (link)
  10. ISBN 978-0-87590-315-6
    .
  11. ^
    ISBN 978-92-64-00994-3
    .
  12. ^ "Archived copy" (PDF). Archived from the original (PDF) on 28 July 2011. Retrieved 6 July 2010.{{cite web}}: CS1 maint: archived copy as title (link)
  13. ^ NGDC. "Comments for the Tsunami Event". Retrieved 6 July 2010.
  14. ^ NGDC. "Tsunami Runups". Retrieved 6 July 2010.
  15. ISBN 978-0-415-47592-1
    .
  16. ^ Rincon, Paul (15 March 2011). "Japan tsunami 'could be 1,000-year event'". BBC News. Archived from the original on 17 March 2011. Retrieved 17 March 2011.

External links

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