Supershear earthquake
Part of a series on |
Earthquakes |
---|
In
Rupture propagation velocity
During seismic events along a fault surface the displacement initiates at the focus and then propagates outwards. Typically for large earthquakes the focus lies towards one end of the slip surface and much of the propagation is unidirectional (e.g. the
Occurrence
Evidence of rupture propagation at velocities greater than S-wave velocities expected for the surrounding crust have been observed for several large earthquakes associated with strike-slip faults. During strike-slip, the main component of rupture propagation will be horizontal, in the direction of displacement, as a Mode II (in-plane) shear crack. This contrasts with a dip-slip rupture where the main direction of rupture propagation will be perpendicular to the displacement, like a Mode III (anti-plane) shear crack. Theoretical studies have shown that Mode III cracks are limited to the shear wave velocity but that Mode II cracks can propagate between the S and P-wave velocities[9] and this may explain why supershear earthquakes have not been observed on dip-slip faults.
Initiation of supershear rupture
The rupture velocity range between those of Rayleigh waves and shear waves remains forbidden for a Mode II crack (a good approximation to a strike-slip rupture). This means that a rupture cannot accelerate from Rayleigh speed to shear wave speed. In the "Burridge–Andrews" mechanism, supershear rupture is initiated on a 'daughter' rupture in the zone of high shear stress developed at the propagating tip of the initial rupture. Because of this high stress zone, this daughter rupture is able start propagating at supershear speed before combining with the existing rupture.[10] Experimental shear crack rupture, using plates of a photoelastic material, has produced a transition from sub-Rayleigh to supershear rupture by a mechanism that "qualitatively conforms to the well-known Burridge-Andrews mechanism".[11]
Geological effects
The high rates of strain expected near faults that are affected by supershear propagation are thought to generate what is described as pulverized rocks. The pulverization involves the development of many small microcracks at a scale smaller than the grain size of the rock, while preserving the earlier
Examples
Directly observed
- North Anatolian Fault Zone[13]
- 1999 Düzce earthquake, magnitude Mw 7.2 associated with strike-slip movement on the North Anatolian Fault Zone[13]
- 2002 Denali earthquake, magnitude Mw 7.9 associated with strike-slip movement on the Denali Fault[15][16]
- 2008 Sichuan earthquake, magnitude Mw 7.9 associated with strike-slip movement on the Longmenshan Fault[17]
- 2010 Yushu earthquake, magnitude Mw 6.9 associated with strike-slip movement on the Yushu Fault[18]
- 2012 Indian Ocean earthquakes, magnitude Mw 8.6 associated with strike-slip on several fault segments - the first supershear event recognised in oceanic lithosphere.[19]
- 2013 Craig, Alaska earthquake, magnitude Mw 7.6 associated with strike-slip on the Queen Charlotte Fault - the first supershear event recognised on an oceanic plate boundary.[20]
- 2013 Balochistan earthquake Mw 7.7 associated with strike-slip movement on a curved fault with supershear rupture speed.[21]
- 2014 Aegean Sea earthquake, magnitude Mw 6.9, supershear was recognised during the second sub-event.[22]
- 2015 Tajikistan earthquake, magnitude Mw 7.2, supershear slip on two segments, with normal slip at the restraining bend linking them.[23]
- 2016 Romanche fracture zone earthquake, magnitude 7.1, westwards-directed supershear rupture following an initial easterly-travelling phase on the Romanche ocean transform fault in the equatorial Atlantic[24]
- 2017 Komandorsky Islands earthquake, magnitude Mw 7.7, supershear transition followed a rupture jump across a fault stepover.[25]
- 2018 Swan Islands earthquake, Mw 7.5 earthquake consisted of three sub-events with a compact rupture area and large cosesimic slip.[26]
- 2018 Sulawesi earthquake, magnitude Mw 7.5, associated with strike-slip movement on the Palu-Koro Fault[27]
- 2020 Caribbean Sea earthquake, magnitude Mw 7.7, unilateral rupture propagation westward from the epicenter along a 300 km section of the Oriente transform fault with two episodes of supershear rupture[28]
- 2021 Maduo earthquake, Mw 7.4 earthquake in the Tibetan Plateau. This earthquake ruptured bilaterally for a length of 170 km within the Bayan Har block.[29]
Inferred
- 1906 San Francisco earthquake, magnitude Mw 7.8 associated with strike-slip movement on the San Andreas Fault[32]
- Imperial Fault[4]
- 1990 Sakhalin earthquake, Mw 7.2 earthquake at over 600 km depth inferred to have ruptured at supershear speeds.[33][34]
- 2013 Okhotsk Sea earthquake magnitude Mw 6.7 aftershock was an extremely deep (640 kilometers (400 miles)) supershear as well as unusually fast at "eight kilometers per second (five miles per second), nearly 50 percent faster than the shear wave velocity at that depth."[35]
See also
References
- ^ Levy D. (December 2, 2005). "A century after the 1906 earthquake, geophysicists revisit 'The Big One' and come up with a new model". Press release. Stanford University. Archived from the original on January 29, 2008. Retrieved June 12, 2008.
- .
- S2CID 120086779.
- ^ a b Archuleta,R.J. 1984. A faulting model for the 1979 Imperial Valley earthquake, J. Geophys. Res., 89, 4559–4585.
- ^ Ellsworth,W.L. & Celebi,M. 1999. Near Field Displacement Time Histories of the M 7.4 Kocaeli (Izimit), Turkey, Earthquake of August 17, 1999, Am. Geophys. Union, Fall Meeting Suppl. 80, F648.
- .
- S2CID 29883938.
- ISSN 0012-821X.
- ISBN 978-0-521-65540-8.
- ISBN 9780444534637.
- ^ Xia, K.; Rosakis, A.J.; Kanamori, H. (2005). "Supershear and sub-Rayleigh to Supershear transition observed in laboratory earthquake experiments" (PDF). Experimental Techniques. Retrieved 28 April 2012.
- doi:10.1038/ngeo640.
- ^ a b [1] Archived 2006-02-14 at the Wayback Machine Bouchon, M., M.-P. Bouin, H. Karabulut, M. N. Toksöz, M. Dietrich, and A. J. Rosakis (2001), How Fast is Rupture During an Earthquake ? New Insights from the 1999 Turkey Earthquakes, Geophys. Res. Lett., 28(14), 2723–2726.]
- S2CID 26437293.
- ^ .
- .
- .
- ]
- .
- S2CID 3754158.
- S2CID 130332801.
- .
- .
- S2CID 221111789.
- .
- S2CID 241109747.[permanent dead link]
- S2CID 133771692.
- S2CID 230613656.
- S2CID 247485288.
- doi:10.31223/X5W95G.
- S2CID 257520761.
- ^ Song,S. Beroza,G.C. & Segall,P. 2005. Evidence for supershear rupture during the 1906 San Francisco earthquake. Eos.Trans.AGU, 86(52), Fall Meet.Suppl., Abstract S12A-05
- S2CID 26550100.
- ^ "M 7.2 - 16 km WSW of Uglegorsk, Russia". earthquake.usgs.gov. Retrieved 20 August 2021.
- ^ "Researchers find evidence of super-fast deep earthquake". Phys.org. July 10, 2014. Retrieved July 10, 2014.
Further reading
- Wang, Dun, Jim Mori, and Kazuki Koketsu. "Fast rupture propagation for large strike-slip earthquakes." Earth and Planetary Science Letters 440 (2016): 115-126.https://doi.org/10.1016/j.epsl.2016.02.022
- Bao, Han; Xu, Liuwei; Meng, Lingsen; Ampuero, Jean-Paul; Gao, Lei; Zhang, Haijiang (2022). "Global frequency of oceanic and continental supershear earthquakes". Nature Geoscience. 15 (11): 942–949. S2CID 253312187.
- Xu, Shiqing, Eiichi Fukuyama, Futoshi Yamashita, Hironori Kawakata, Kazuo Mizoguchi, and Shigeru Takizawa. "Fault strength and rupture process controlled by fault surface topography." Nature Geoscience (2023): 1-7.https://doi.org/10.1038/s41561-022-01093-z
- Richard Fisher (29 July 2009), "Seismic boom: Breaking the quake barrier", New Scientist