Postseismic displacements following the 2007 Noto peninsula earthquake detected by dense GPS observation

Abstract

We have been conducting dense GPS observation in and around the epicentral region of the 2007 Noto peninsula earthquake since March 25, 2007, in order to detect postseismic displacements. Continuous observation has been underway at 12 sites to fill the gap of GEONET. Preliminary analysis of data up to early May shows that initial postseismic displacement rapidly decayed within 20 days after the occurrence of the mainshock. Horizontal displacements do not exceed 20 mm even at sites above the aftershock zone for this period. We also found a maximum uplift of about 20 mm there. Inversion of postseismic displacements with the variable slip model suggests a nearly right-lateral afterslip of less than 5 cm on the shallow portion of the source fault. Fitting a theoretical function to a time series of coordinate changes also suggests that the observed postseismic displacements might have been generated by afterslip.

Relation between similar aftershocks and ruptured asperity of a large inland earthquake: Example of the 2007 Noto Hanto earthquake

“…We cannot, however, find such a relationship between spatial distribution of the coseismic slip (Horikawa, 2008) and that of the afterslip (Hashimoto et al, 2008) for the 2007 Noto Hanto earthquake. One of the reasons why no relationship is found is a poor spatial resolution of the afterslip distribution of the 2007 Noto Hanto earthquake.…”

“…Nineteen groups are lying on the fault plane, and 11 groups are on the conjugate fault. Hereafter, we focus on the groups lying on the source fault plane to investigate spatial relationship among the similar earthquakes, the asperity (Horikawa, 2008), and the afterslip (Hashimoto et al, 2008). We use the source fault plane of Horikawa (2008), which has the same area as the aftershock distribution during the first day after the mainshock.…”

“…Inversion analyses of geodetic data (e.g. Fukushima et al, 2008) and strong motion data (e.g. Horikawa, 2008) showed that the dominant slip was on a reverse fault with right-lateral slip and that the area of large slip, or asperity, was distributed from the hypocenter to the shallow part of the fault plane.…”

“…Horikawa, 2008) showed that the dominant slip was on a reverse fault with right-lateral slip and that the area of large slip, or asperity, was distributed from the hypocenter to the shallow part of the fault plane. Hashimoto et al (2008) started GPS observations during the period from 25 to 29 March 2007 and continued these for about 40 days after the earthquake. They reported that the initial postseismic displacement rapidly decayed within 20 days after the occurrence of the mainshock and suggested a nearly pure right-lateral afterslip of less than Copyright c The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.…”

Postseismic slip associated with the 2007 Chuetsu-oki, Niigata, Japan, Earthquake (M 6.8 on 16 July 2007) as inferred from GPS data

“…This idea is also implied by the analysis of InSAR (Ozawa et al, 2005). Nakao et al (2006) and Hashimoto et al (2008) detected postseismic slip shallower than the main shock in the 2005 West Off Fukuoka Prefecture Earthquake (M 7.0) and the Noto Hanto Earthquake in 2007 (M 6.9), respectively. The postseismic slip associated with the COE possibly occurred also in the shallow part, and the results of our inversion analysis support this idea.…”