Average slip rate at the transition zone on the plate interface beneath the Kii Peninsula, Japan, estimated from deep low-frequency tremors

Ryosuke Ishida,Yoshihiro Hiramatsu,Kazushige Obara,Takanori Matsuzawa

doi:10.5047/eps.2013.04.003

Abstract

We investigated the average slip rate at the transition zone on the plate interface beneath the Kii Peninsula, Japan, using an empirical method based on a proportional relation of sizes between short-term slow slip events and nonvolcanic deep low-frequency tremors. The estimated average slip rates are 3.0±0.4 cm/yr, 2.6±0.4 cm/yr, and 2.4±0.4 cm/yr, in the northern, central, and southern Kii Peninsula, respectively. Values in the northern and the central areas compensate for the difference between the slip deficit rate at the transition zone and the convergence rate of the subducting Philippine Sea plate. The discrepancy among those rates is, however, large in the southern area, suggesting a lateral variation in the proportional relation or the existence of a steady, or quasi-steady, slip.

Highlights

Recent seismological and geodetic observations from dense networks have revealed various characteristic phenomena in subduction zones, especially during interseismic periods, such as nonvolcanic deep low-frequency (DLF) tremors (e.g. Obara, 2002), and short-term and long-term slow slip events (SSE) (e.g. Hirose and Obara, 2005)
We show the temporal variation in the cumulative seismic moment during January 2001–May 2009 at the transition zone on the plate interface in the northern, central, and southern areas estimated from the DLF tremors with projected on the plate interface with a dip of 20◦, which is the average dip of the source faults of the short-term SSEs observed geodetically (NIED, 2009; Sekine et al, 2010)
In terms of the slip rate at the transition zone, the slip deficit rate on the plate interface is an important parameter estimated from GPS data

Summary

Introduction

Recent seismological and geodetic observations from dense networks have revealed various characteristic phenomena in subduction zones, especially during interseismic periods, such as nonvolcanic deep low-frequency (DLF) tremors (e.g. Obara, 2002), and short-term and long-term slow slip events (SSE) (e.g. Hirose and Obara, 2005). SSEs (Obara et al, 2004) and have reported the cause of DLF tremors as the shear slip process (Shelly et al, 2006; Ide et al, 2007) Based on these features, Hiramatsu et al (2008) proposed an empirical method to estimate the average slip rate at the transition zone on the plate interface using the DLF tremors. We used a hypocenter catalog of the DLF tremors determined routinely using the envelope correlation method developed by NIED (Obara, 2002; Obara and Hirose, 2006) This catalogue was used for the estimation of the average slip rate in the transition zones on the plate interface in the Shikoku regions (Hirose et al, 2010). We adopted the conversion factor estimated in the northern area for use for DLF tremors in the central and southern areas

Average Slip Rate on the Plate Interface Estimated from DLF Tremors

Discussion and Concluding