Seismicity and focal mechanisms of the Arctic region and the North American plate boundary in Asia

Abstract

Although Arctic earthquakes have been recorded since 1908, detailed study of them has been hampered due to the lack of seismograph stations and the infrequent occurrence of large earthquakes north of the Arctic Circle. Detailed analysis of Arctic earthquakes began during the International Geophysical Year (IGY, 1957–1958), and subsequent studies have been facilitated by the development of the World-Wide Standardized Seismograph Network (WWSSN) starting in 1963. Many authors have published summaries of Arctic seismicity. The pre-IGY state of knowledge is summarized by Hodgson and others (1965), and epicentral coordinates and magnitude estimates of pre-WWSSN seismicity are given in Gutenberg and Richter (1954), Linden (1961), Hodgson and others (1965), and Rothe (1969). Overview summaries of the distribution and magnitude of Arctic seismicity are presented by Sykes (1965) and Wetmiller and Forsyth (1978). Numerous maps of Arctic seismicity have been published (e.g., Veis-Ksenofontova, 1962; Sykes, 1965; Barazangi and Dorman, 1970; Tarr, 1970; Wetmiller, 1978; Avetisov and Sokolova, 1980). Additional details about Arctic seismicity are given in international bulletins, national seismicity summaries, and annual reports. In this chapter we summarize the development of seismograph stations in the Arctic, the distribution of seismicity in the Arctic, focal mechanisms that have been determined for the Arctic seismic zone, including northeastern Siberia and Baffin Bay, and the implications of the seismic data for plate tectonic models of the region. In addition, we summarize inferences on crustal structure of the Arctic region based on the propagation characteristics of earthquake waves.

Seismotectonics of the Chersky Seismic Belt, eastern Sakha Republic (Yakutia) and Magadan District, Russia

“…All earthquakes on the shelf have extensional or transtensional mechanisms (Chapman and Solomon, 1976;Jemsek et al, 1986;Fujita et al, 1990aFujita et al, , 1990bAvetisov, 1993Avetisov, , 1996, with one or both nodal planes parallel to the strike of the grabens. Focal depths generally increase from 10 to 20 km towards the south (Jemsek et al, 1986).…”

“…From the Laptev Sea, some workers (e.g., Chapman and Solomon, 1976;DeMets, 1992;Steblov et al, 2003) favor extending the North America-Eurasia boundary south across northeast Russia to join with the seismicity of Sakhalin Island, then on to northern Japan, attaching the Okhotsk region to the North American plate. Others (e.g., Zonenshayn et al, 1978;Savostin and Karasik, 1981;Cook et al, 1986;Parfenov et al, 1988;Fujita et al, 1990aFujita et al, , 1997Riegel et al, 1993;Seno et al, 1996) prefer to have the North America boundary follow the band of earthquakes along the Chersky Range to northern Kamchatka and suggest that the Sea of Okhotsk, Kamchatka, northern Japan, eastern Sakhalin, and the area around Magadan comprise a separate Okhotsk microplate or block. The present-day geodynamics of northeast Asia is controlled by the interactions of the Eurasian, North American, and Pacific plates (Fig.…”

“…The present-day geodynamics of northeast Asia is controlled by the interactions of the Eurasian, North American, and Pacific plates (Fig. 1 inset; Cook et al, 1986;Parfenov et al, 1988;Fujita et al, 1990aFujita et al, , 1997, and possibly the presumed far-field effects of the Indian plate (e.g., Peltzer and Tapponnier, 1988;Worrall et al, 1996). The movement of these giant plates with respect to each other has resulted in the development of diffuse seismic zones between them and the apparent formation of at least three independent blocks or microplates (Fig.…”

“…2; Tarr, 1970;Savostin and Karasik, 1981;Cook et al, 1986;Parfenov et al, 1988;Imaev et al, 1990;Fujita et al, 1990a). In the Arctic Ocean, the seismicity forms a narrow band of primarily normal faulting earthquakes along the Arctic (Gakkel) Mid-Ocean Ridge (Savostin and Karasik, 1981;Cook et al, 1986;Jemsek et al, 1986;Fujita et al, 1990a;Avetisov, 1996), which represents the locus of sea-floor spreading (e.g., Wilson, 1963;Vogt et al, 1979;Cochran et al, 2003).…”

Minimal late Holocene sea level rise in the Chukchi Sea: arctic insensitivity to global change?

“…Sporadic 20th century seismic activity is documented adjacent the eastern Chukchi Sea, with only two earthquakes of magnitude 5.0 to 6.0 during the last 70 years (Fujita et al, 1990). Despite this activity, co-seismic elevation changes are not detectable during the Holocene, as indicated by the position (8-10 m above MSL) of the Last Interglacial (Isotope stage 5e) shoreline (Hamilton and Brigham-Grette, 1991, p. 64) that may reflect only several meters of uplift over 125,000 years.…”