Temporal change of the vertical crustal movement on the western coast of Suruga Bay, central Japan

Correlating seismicity parameters and subsidence in the Tokai region, central Japan

“…A scatterplot of b value versus subsidence rate (Figure 2, inset) illustrates this coincidence further. The spatial correlation of the two observations is also reasonable: the strongest subsidence is located in the northeastern corner of their analyzed region [ Takayama and Yoshida , 2002, Figure 10], coinciding with part of the b value decrease (Figure 7c). However, because the geodetic measurements are limited to a subregion, we are not able to quantify this spatial correlation.…”

“…Long‐term monitoring of subsidence there has revealed a steady subsidence, interrupted by an accelerated episode around 1988–1989. This has been investigated in detail by Takayama and Yoshida [2002], whose findings we summarize in Figure 2. When the seasonally adjusted time series of subsidence obtained from Takayama and Yoshida [2002, Figure 3d] (averaging time window 1 year) is plotted along with the change in b value, coincidence between the two transients is very clear (Figure 2): Large subsidence corresponds to large b values.…”

“…From recent geodetic surveys, a fairly detailed model of the locked plate boundary between the subducting Philippine Sea and Eurasian plates [ Hirono , 2003; Kuroki et al , 2002; Sagiya , 1999] exists. Takayama and Yoshida [2002] suggested that the accelerated subsidence on the western coast of Suruga Bay in the late 1980s indicates a strengthened interplate coupling in its shallower part, which they have named a “slow stick” event. The observation of more thrust‐type earthquakes in the Suruga Bay region in the late 1980s (Figure 12) supports this hypothesis, because thrusting style faulting is observed in the locked zone and our results suggest either grows of the locked zone of stronger coupling within that zone.…”

“…Recent evidence for this is the slow slip event that started in 2001 and is clearly detected with the modern GPS network [ Fujii et al , 2001; Ozawa et al , 2002]. Besides that, recent reinvestigation of the spatial and temporal patterns of vertical crustal movement in the eastern Tokai region over the past 38 years has revealed significant changes in subsidence rate [ Takayama and Yoshida , 2002]. Their study was based on measurements by GSI along the leveling route between Kakegawa (BM140‐1) and Hamaoka (BM25951) (Figure 1).…”

“…The subsidence data are based on leveling measurements performed by the Geographical Survey Institute, showing subsidence at Hamaoka (BM25951) relative to Kakegawa (BM140‐1). Trend and seasonal effects were removed and data averaged for a 1‐year period (see Takayama and Yoshida [2002] for details).…”