Accelerated pacific plate subduction following interplate thrust earthquakes at the Japan trench

Abstract

Interplate thrust earthquakes are usually followed by afterslips, and they let the fore-arc move slowly trenchward. However, we do not know if the subducting oceanic plate is accelerated landward after such earthquakes. The westward velocity of Global Positioning System (GPS) stations in NE Japan show gradient decreasing from east to west reflecting the E-W contractional strain built up by the inter-plate coupling. Here we show that such coupling significantly enhanced (~1.5 times) after the 2003 Tokachi-Oki earthquake (M w 8.0), Hokkaido, in the segments adjacent to the ruptured fault. The coupling seems to be further enhanced (~3 times) after the 2011 Tohoku-Oki earthquake (M w 9.0). It is unlikely that interplate friction suddenly increased over such a large region, and relatively strong pre-2003 coupling there would not allow such enhancements even if full coupling is attained. Hence they are attributable to the temporary acceleration of the Pacific Plate subduction. We propose a simple 2-dimensional model in which down-dip acceleration of the slab let the force balance rapidly recover promoted by a thin low-viscosity layer on the slab surface. The accelerated subduction would account for temporary activations of regional interplate seismicity after megathrust earthquakes.

A very long-term transient event preceding the 2011 Tohoku earthquake

“…The northern source for the westward deviations was interpreted previously to be a result of recovery of plate coupling 10 or temporary acceleration of subduction 21 . These interpretations cannot be applied to the southern source, because this source generated deviations in the opposite direction.…”

Effect of the volcanic front migration on helium, nitrogen, argon, and carbon geochemistry of hydrothermal/magmatic fluids from Hokkaido volcanoes, Japan

“…The Tokachi-Oki earthquake (M8.0) was recorded in 2003. Studies show that this earthquake produced accelerated plate subduction, caused local concentration of strain and resulted in inland earthquakes in the Meakan Area (Heki and Mitsui, 2013;Ichihara et al, 2013). The measured SO 2 and CO 2 in 2003 from Tokachi are 2.4 kg/s and 3 kg/s, respectively.…”

Block motion changes in Japan triggered by the 2011 great Tohoku earthquake

“…At smaller spatial scales (1000 km) and shorter temporal scales (<10,000 years), earthquake and fault activity at some plate boundaries has also been found to be irregular in time [Bennett et al, 2004;Dolan et al, 2007Dolan et al, , 2016. A geodetically based inference of accelerated Pacific plate subduction following the 2011 Tohoku, Japan earthquake may provide an example of the direct observation of this type of behavior [Heki and Mitsui, 2013]. A geodetically based inference of accelerated Pacific plate subduction following the 2011 Tohoku, Japan earthquake may provide an example of the direct observation of this type of behavior [Heki and Mitsui, 2013].…”