The 2006–2007 Kuril Islands great earthquake sequence

Abstract

The southwestern half of a ∼500 km long seismic gap in the central Kuril Island arc subduction zone experienced two great earthquakes with extensive preshock and aftershock sequences in late 2006 to early 2007. The nature of seismic coupling in the gap had been uncertain due to the limited historical record of prior large events and the presence of distinctive upper plate, trench and outer rise structures relative to adjacent regions along the arc that have experienced repeated great interplate earthquakes in the last few centuries. The intraplate region seaward of the seismic gap had several shallow compressional events during the preceding decades (notably an MS 7.2 event on 16 March 1963), leading to speculation that the interplate fault was seismically coupled. This issue was partly resolved by failure of the shallow portion of the interplate megathrust in an MW = 8.3 thrust event on 15 November 2006. This event ruptured ∼250 km along the seismic gap, just northeast of the great 1963 Kuril Island (Mw = 8.5) earthquake rupture zone. Within minutes of the thrust event, intense earthquake activity commenced beneath the outer wall of the trench seaward of the interplate rupture, with the larger events having normal‐faulting mechanisms. An unusual double band of interplate and intraplate aftershocks developed. On 13 January 2007, an MW = 8.1 extensional earthquake ruptured within the Pacific plate beneath the seaward edge of the Kuril trench. This event is the third largest normal‐faulting earthquake seaward of a subduction zone on record, and its rupture zone extended to at least 33 km depth and paralleled most of the length of the 2006 rupture. The 13 January 2007 event produced stronger shaking in Japan than the larger thrust event, as a consequence of higher short‐period energy radiation from the source. The great event aftershock sequences were dominated by the expected faulting geometries; thrust faulting for the 2006 rupture zone, and normal faulting for the 2007 rupture zone. A large intraplate compressional event occurred on 15 January 2009 (Mw = 7.4) near 45 km depth, below the rupture zone of the 2007 event and in the vicinity of the 16 March 1963 compressional event. The fault geometry, rupture process and slip distributions of the two great events are estimated using very broadband teleseismic body and surface wave observations. The occurrence of the thrust event in the shallowest portion of the interplate fault in a region with a paucity of large thrust events at greater depths suggests that the event removed most of the slip deficit on this portion of the interplate fault. This great earthquake doublet demonstrates the heightened seismic hazard posed by induced intraplate faulting following large interplate thrust events. Future seismic failure of the remainder of the seismic gap appears viable, with the northeastern region that has also experienced compressional activity seaward of the megathrust warranting particular attention.

Subduction zone megathrust earthquakes

“…Very shallow megathrust slip also occurred in the 2006 M w 8.3 Kuril earthquake, an area also lacking in previous interplate seismicity (Ammon et al, 2008;Lay et al, 2009). …”

“…Normal faulting aftershocks have been observed after many large megathrust ruptures (Fig. 18), particularly those that rupture very shallowly near a trench (e.g., Kanamori, 1971;Christensen and Ruff, 1988;Lin and Stein, 2004;Ammon et al, 2008;Lay et al, 2009;Asano et al, 2011;El Hariri and Bilek, 2011;Bilek et al, 2011;Ide et al, 2011;Kato et al, 2011;Lange et al, 2012;Rietbrock et al, 2012;Yue et al, 2014b;Wetzler et al, 2017;Sladen and Trevisan, 2018). Some of these intraplate extensional events are within the outer rise, seaward of the trench, or on plate-bending related faults below the megathrusts, while others are found within the upper plate adjacent to the zone of high slip (e.g., Farías et al, 2011;Hicks and Rietbrock, 2015).…”

“…In contrast, the Sumatra subduction zone has experienced several great thrust earthquakes since The Honshu, Japan, subduction zone has hosted three great thrust earthquakes since 1900, with the largest being the 2011 (Tohoku, M w 9.1) event in 2011, followed by the 1968 (Tokachi-oki, M w 8.2) and 1960 (Sanriku, M w 8.0; possibly an overestimated magnitude) earthquakes. The 2011 event appears to have reruptured a significant portion of the 1896 Meiji Sanriku tsunami earthquake zone on the shallow portion of the megathrust near the trench from 38°N to 40.3°N (e.g., Yamazaki et al, 2018;Lay, 2017 (Ammon et al, 2008;Lay et al, 2009), given that it immediately activated outer-rise faulting aftershocks. The 2003 Hokkaido rupture zone closely overlaps the 1952 zone.…”

Using centroid time-delays to characterize source durations and identify earthquakes with unique characteristics

“…Rupture duration measurements provided in the literature for ! ≥ 6.5 earthquakes are compared with duration estimated from our time--shift measurements (Abercrombie et al, 2003;Antolik et al, 2006;Houston et al, 1998;Lay et al, 2010a;2010b;Lay et al, 2009;Sladen, 2009a;2009b;2008a;2008b;2007a;2007b;Kikuchi, written communication, 2001;Tanioka and Ruff, 1997;Tocheport et al, 2006;Yagi, 2004;2003;2002). R o m a n c h e 1 9 9 4 S a n t a -C ru z Is .1 9 9 9…”

Some Preliminary Results on the Distribution of Aftershock Sequences in Japan-Kuril Islands and Kamchatka

“…A large number of studies which focus on the properties of aftershock sequences have been published during the last decades (Tsapanos, 1990(Tsapanos, , 1992Drakatos, 2000;Henry and Das, 2001;Felzer et al, 2004;Shcherbakov et al, 2005;Schorlemmer et al, 2005;Lay et al, 2009;Marsan and Lengliné, 2010;Goda, 2012;Scholz and Campos, 2012;Shcherbakov et al, 2013;MousaviBafrouei et al, 2014;among others). Moment release rates during mainshocks compared with moment release rates during aftershock sequences showed that the moment release rates of aftershock sequence are 30 times smaller than the maximum moment rate of the main shock (Kagan and Houston, 2005) It is well known that aftershock sequences follow statistical laws.…”