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  • 21 Aug, 2019

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1979 Yapen Earthquake
The 1979 Yapen earthquake occurred on September 12 at 05:17:51 UTC. It had an epicenter near the coast of Yapen Island in Irian Jaya, Indonesia. Measuring 7.5 on the moment magnitude scale and having a depth of 20 km (12 mi), it caused severe damage on the island. At least 115 were killed due to shaking and a moderate tsunami.

Tectonic setting

The northern coast of New Guinea is situated in a region of east–west oblique plate convergence between the Australian and Pacific plates. The oceanic crust of the Pacific plate subducts obliquely beneath New Guinea and nearby islands along the New Britain Trench and Manokwari Trough. A large component of this oblique convergence is accommodated by east–west left-lateral shear at a rate of 80 mm/yr. The shear zone is approximately 300 km (190 mi) long and is a complex zone of faults. The Sorong, Koor, Ransiki and Yapen faults are the largest structures forming the shear zone.

Earthquake

The earthquake occurred due to left-lateral strike-slip faulting on the 420 km (260 mi) long Yapen Fault. The Yapen Fault is the fastest-slipping fault in the shear zone, estimated to move at a rate of 46 ± 12 mm/yr. It crosses east–west through Cenderawasih Bay. Seismologist Emile A. Okal estimated that the rupture produced up to 2 m (6 ft 7 in) of displacement on an east-southeast–west-northwest fault. The total rupture length was 75 km (47 mi) × 35 km (22 mi). A study in 2002 estimated the rupture to be 80 km (50 mi) × 15 km (9.3 mi) and producing up to 7 m (23 ft) of slip. It was followed by an aftershock sequence trending east–west. A cluster of aftershocks occurred north of the mainshock, at Pandaidori, displayed reverse faulting. This aftershock sequence is thought to be triggered by stress transfer.

Damage

Shaking from the mainshock killed 15 people and demolished at least 1,000 homes. Despite being a strike-slip earthquake, slip of up to 2 m (6 ft 7 in) was sufficient to generate a moderate tsunami near the coastline. Waves measuring 2 m (6 ft 7 in) was recorded at Biak. The tsunami killed at least 100 people on Yapen Island. A fisherman on Biak was among the fatalities after being swept away by the waves. In West Yapen District, 76 homes were destroyed and flooded by the tsunami. Many residents had to hold themselves onto stable objects during the shaking. Ground cracks occurred. Many churches and homes collapsed. In two villages, all homes were destroyed. A large fissure up to 1.5 km (0.93 mi) was reported in Serui. In Menawi, 254 homes were seriously damaged. A further 90 homes and a school were destroyed at Randawaya II.

After the earthquake, local government officials in Jayapura were not notified about the earthquake due to a local event. It was only after news was transmitted to Garuda Indonesia in Sentani were they informed. The Indonesian Minister of Home Affairs appointed the Governor of Irian Jaya to respond immediately to the affected area. A total of 16,500 residents were displaced.

See also

References

  1. ^ ISC (2022), ISC-GEM Global Instrumental Earthquake Catalogue (1904–2018), Version 9.0, International Seismological Centre, doi:10.31905/D808B825
  2. ^ "M 7.9 – 55 km S of Biak, Indonesia". United States Geological Survey. Retrieved 17 June 2022.
  3. ^ Okalyear=1999, E. (1999), "Historical Seismicity and Seismotectonic Context of the Great 1979 Yapen and 1996 Biak, Irian Jaya Earthquakes" (PDF), Pure and Applied Geophysics, 154 (3–4): 633–675, Bibcode:1999PApGe.154..633O, doi:10.1007/s000240050247, S2CID 128554047{{citation}}: CS1 maint: numeric names: authors list (link)
  4. ^ "Katalog Gempabumi Signifikan dan Dirasakan". Meteorology, Climatology, and Geophysical Agency. Retrieved 11 August 2021.
  5. ^ National Geophysical Data Center / World Data Service (NGDC/WDS), Global Historical Tsunami Database (Data Set), NOAA National Centers for Environmental Information, doi:10.7289/V5PN93H7, retrieved 10 June 2022
  6. ^ National Geophysical Data Center / World Data Service (NGDC/WDS): NCEI/WDS Global Significant Earthquake Database. NOAA National Centers for Environmental Information (1972), Significant Earthquake Information (Data Set), NOAA National Centers for Environmental Information, doi:10.7289/V5TD9V7K, retrieved 10 June 2022
  7. ^ Tregoning, P.; Gorbatov, A. (2004). "Evidence for active subduction at the New Guinea Trench". Geophysical Research Letters. 31 (13). Bibcode:2004GeoRL..3113608T. doi:10.1029/2004GL020190. S2CID 26940540.
  8. ^ Watkinson, Ian M.; Hall, Robert (2016). "Fault systems of the eastern Indonesian triple junction: evaluation of Quaternary activity and implications for seismic hazards" (PDF). Geological Society, London, Special Publications. 441 (1): 71–120. Bibcode:2017GSLSP.441...71W. doi:10.1144/SP441.8. S2CID 132297395.
  9. ^ Henry, C.; Das, S. (2002). "The Mw 8.2, 17 February 1996 Biak, Indonesia, earthquake: Rupture history, aftershocks, and fault plane properties" (PDF). Journal of Geophysical Research. 107 (B11): ESE 11-1-ESE 11–16. Bibcode:2002JGRB..107.2312H. doi:10.1029/2001JB000796.
  10. ^ Seno, Tetsuzo; Kaplan, David E. (1988). "Seismotectonics of western New Guinea". Journal of Physics of the Earth. 36 (3): 107–124. doi:10.4294/jpe1952.36.107.
  11. ^ Retia Kartika Dewi (12 September 2020). Rizal Setyo Nugroho (ed.). "Hari Ini dalam Sejarah: Gempa Yapen, Papua 8,1 M, 16.500 Warga Kehilangan Rumah" [Today in History: Yapen Earthquake, Papua 8.1 M, 16,500 Residents Lost Their Homes]. Kompas (in Indonesian). Retrieved 17 June 2022.
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