Abstract
Seismicity characteristics in the Cascadia subduction zone located west of North America are considered. It has been established that, since 1964, shallow (h = 0–33 km) ring-shaped seismicity structures with threshold magnitudes Mt of 4.4 and 4.6, respectively, have been formed prior to two large earthquakes (on August 17, 1991, Mw = 7.1 and April 25, 1992, Mw = 7.2). Note that, unlike many other subduction zones, deep ring-shaped structures (h = 34–70 km) have not been observed here. At the same time, deep seismicity strips are sometimes formed in this zone. Two new ring-shaped structures with Mt equal to 5.0 and 5.2, which began to form here since 1973, are distinguished. There are grounds to suppose that large earthquakes can be expected in the regions of these structures. We estimate the magnitudes of possible large earthquakes: Mw = 7.8 and 7.9 on the basis of the correlation dependences of the seismicity ring sizes and Mt values on the magnitudes of major events obtained earlier for the East Pacific. These data allowed us to conclude that processes of preparation for a great earthquake with Mw ~ 9.0, similar to the 1700 event, did not begin in the subduction zone. At the same time, a large earthquake (Mw = 7.9 ± 0.1) is possible in a few years in the region of Vancouver Island. We suppose that the formation of shallow rings and deep strips of seismicity is related to deep fluid migration, as occurs in other regions.
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REFERENCES
Abers, G., Nakajima, J., van Keken, P., Kita, S., and Hacker, B., Thermal–petrological controls on the location of earthquakes within subducting plates, Mar. Geol., 2013, vols. 369–370, pp. 178–187.
Goldfinger, C., Ikeda, Ya., Yeats, R., and Ren, J., Superquakes and supercycles, Seismol. Res. Lett., 2013, vol. 84, no. 1, pp. 24–32.
Kopnichev, Yu.F. and Sokolova, I.N., Ring seismicity in different depth ranges before large and great earthquakes in subduction zones, Dokl. Earth Sci., 2009a, vol. 425, no. 2, pp. 448–450.
Kopnichev, Yu.F. and Sokolova, I.N., Characteristics of ring seismicity in different depth ranges before large and great earthquakes in the Sumatra region, Dokl. Earth Sci., 2009b, vol. 429, no. 1, pp. 1385–1388.
Kopnichev, Yu.F. and Sokolova, I.N., On the correlation between seismicity characteristics and S-wave attenuation in the ring structures that appear before large earthquakes, J. Volkanol. Seismol., 2010, vol. 4, no. 6, pp. 396–411.
Kopnichev, Yu.F. and Sokolova, I.N., Annular seismicity structures and the March 11, 2011, earthquake (M w = 9.0) in Northeast Japan, Dokl. Earth Sci., 2011a, vol. 440, no. 1, pp. 1324–1327.
Kopnichev, Yu.F. and Sokolova, I.N., Inhomogeneities in the field of short-period S-wave attenuation at the source of the Maule (Chili, February 27, 2010; M w = 8.8) earthquake and their correlation with seismicity and the regional volcanism, Geofiz. Issled., 2011b, vol. 12, no. 3, pp. 22–33.
Kopnichev, Yu.F. and Sokolova, I.N., Ring seismicity structures in different depth ranges before large and greatest earthquakes in the Aleutian and Alaska regions, Vestn. Nats. Yad. Tsentra Resp. Kaz., 2012, no. 1, pp. 137–146.
Kopnichev, Yu.F. and Sokolova, I.N., Characteristics of ring structures of seismicity generated before large and greatest earthquakes in the Pacific periphery, Vestn. Nats. Yad. Tsentra Resp. Kaz., 2013, no. 2, pp. 131–140.
Kopnichev, Yu.F. and Sokolova, I.N., Ring structures of seismicity in northern Chile and a successful forecast of the place and magnitude of the Iquique earthquake on April 1, 2014 (M w = 8.2), Vestn. Nats. Yad. Tsentra Resp. Kaz., 2015, no. 4, pp. 153–159.
Kopnichev, Yu.F. and Sokolova, I.N., Ring structures of seismicity in Southern Mexico: Possible preparation of a large earthquake, Vestn. Nats. Yad. Tsentra Resp. Kaz., 2016, no. 4, pp. 24–29.
Kulkarni, R., Wong, I., Zachariasen, J., Goldfinger, C., and Lawrence, M., Statistical analysis of great earthquake recurrence along the Cascadia subduction zone, Bull. Seismol. Soc. Am., 2013, vol. 103, no. 6, pp. 3205–3221.
Letnikov, F.A., Sinergetika geologicheskikh sistem (Synergetics of Geological Systems), Novosibirsk: Nauka, 1992.
Satake, K., Wang, K., and Atwater, B., Fault slip and seismic moment of the 1700 Cascadia earthquake inferred from Japanese tsunami descriptions, J. Geophys. Res., 2003, vol. 108, no. B11. doi 10.1029/2003JB002521
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Translated by E. Morozov
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Kopnichev, Y.F., Sokolova, I.N. Ring-Shaped Seismicity Structures in the Cascadia Subduction Zone: Possible Upcoming Large Earthquakes. Izv. Atmos. Ocean. Phys. 54, 745–752 (2018). https://doi.org/10.1134/S0001433818070046
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DOI: https://doi.org/10.1134/S0001433818070046