Precise aftershock distribution of the 2005West Off Fukuoka Prefecture Earthquake (Mj=7.0) using a dense onshore and offshore seismic network

Uehira, Kenji; Yamada, Tomoaki; Shinohara, Masanao; Nakahigashi, Kazuo; Miyamachi, Hiroki; Iio, Yoshihisa; Okada, Tomomi; Takahashi, Hiroaki; Matsuwo, Norimichi; Uchida, Kazunari; Kanazawa, Toshihiko; Shimizu, Hiroshi

doi:10.1186/bf03352669

Cited by 22 publications

(23 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In addition, the area of high seismicity within 1 week after the mainshock did not overlap with the large coseismic slip area, although some aftershocks with relatively small magnitude (M < 3) occurred on R1. The feature that aftershocks are not active where coseismic slips are large in the mainshock has also been found in other crustal strike-fault-type earthquakes in Japan: the 1995 south Hyogo (Kobe) earthquake (M JMA 7.2) (e.g., Hirata et al 1996;Ide et al 1996), the 2000 western Tottori earthquake (e.g., Ohmi et al 2002;Semmane et al 2005), the 2005 west off Fukuoka earthquake (M JMA 7.0) (e.g., Nishimura et al 2006;Uehira et al 2006), and the first large event (M JMA 6.5, April 14, 2016, JST) of the 2016 Kumamoto earthquakes (e.g., Asano and Iwata 2016; Kubo et al 2016). In the largest event (M JMA 7.3, April 16, 2016, JST) of the 2016 Kumamoto earthquakes, some aftershocks occurred in the area with large coseismic slips along the Futagawa fault, while the number of the aftershocks was relatively small compared to other regions such as the Hinagu fault and the Aso area (e.g., Asano and Iwata 2016; Kubo et al 2016).…”

Section: Methodsmentioning

confidence: 99%

Source rupture process of the 2016 central Tottori, Japan, earthquake (M JMA 6.6) inferred from strong motion waveforms

Kubo

Suzuki

Aoi

et al. 2017

Earth Planets Space

View full text Add to dashboard Cite

The source rupture process of the 2016 central Tottori, Japan, earthquake (M JMA 6.6) was estimated from strong motion waveforms using a multiple-time-window kinematic waveform inversion. A large slip region with a maximum slip of 0.6 m extends from the hypocenter to the shallower part, caused by the first rupture propagating upward 0-3 s after rupture initiation. The contribution of this large slip region to the seismic waves in the frequency band of the waveform inversion is significant at all stations. Another large slip region with smaller slips was found in northnorthwest of the hypocenter, caused by the second rupture propagating in the north-northwest direction at 3-5 s. Although the contribution of this slip region is not large, seismic waveforms radiating from it are necessary to explain the later part of the observed waveforms at several stations with different azimuths. The estimated seismic moment of the derived source model is 2.1 × 10 18 Nm (M w 6.1). The high-seismicity area of aftershocks did not overlap with largeslip areas of the mainshock. Two wave packets in the high frequency band observed at near-fault stations are likely to correspond to the two significant ruptures in the estimated source model.

show abstract

Section: Methodsmentioning

confidence: 99%

Source rupture process of the 2016 central Tottori, Japan, earthquake (M JMA 6.6) inferred from strong motion waveforms

Kubo

Suzuki

Aoi

et al. 2017

Earth Planets Space

View full text Add to dashboard Cite

show abstract

“…The accuracy of the hypocenter locations therefore improved with time, and the most precise hypocenters were obtained from March 27 to April 13 because of the OBS observations. Since details of the hypocenter distribution in the period of OBS observation are discussed by Uehira et al (2006), we limit our discussion in this article to the distribution of aftershocks in the sequence and the fault system inferred from aftershock activity. Figure 2 shows the hypocenter of the mainshock of March 20 and aftershocks from March 20 to April 20.…”

Section: Hypocenter Distribution Of Aftershocksmentioning

confidence: 99%

“…Event detection and the picking of P-and S-wave arrival times were performed using the WIN system (Urabe and Tsukada, 1991), and a maximumlikelihood method was used in the calculation of hypocenter locations (Hirata and Matsu'ura, 1987). In the calculation of hypocenters and focal mechanisms, we assumed the onedimensional velocity structure model used in the data processing at SEVO (see figure 2 of Uehira et al, 2006). The magnitudes of aftershocks were determined using maximum amplitudes of velocity seismograms, which are empirically consistent with JMA magnitudes (Watanabe, 1971).…”

Section: Hypocenter Distribution Of Aftershocksmentioning

confidence: 99%

Aftershock seismicity and fault structure of the 2005 West Off Fukuoka Prefecture Earthquake (MJMA7.0) derived from urgent joint observations

et al. 2006

Self Cite

View full text Add to dashboard Cite

On March 20, 2005, a large M JMA 7.0 earthquake occurred in the offshore area, west of Fukuoka prefecture, northern Kyushu, Japan. A series of joint observations were carried out by teams from several universities in Japan with the aim of investigating the aftershock activity. Six online telemetered and 17 offline recording seismic stations were installed on land around the aftershock area immediately followed the occurrence of the mainshock. Because aftershocks were located mainly in offshore regions, we also installed 11 ocean bottom seismometers (OBSs) just above the aftershock region and its vicinity in order to obtain accurate locations of hypocenters. The OBS observation was carried out from March 27 to April 13, 2005. We further conducted temporary GPS observations in which ten GPS receivers were deployed around the aftershock region. The aftershocks were mainly aligned along an approximately 25-km-long NW-SE trend, and the hypocenters of the main aftershock region were distributed on a nearly vertical plane at depths of 2-16 km. The mainshock was located near the central part of the main aftershock region at a depth of approximately 10 km. The largest aftershock of M JMA 5.8 occurred near the southeastern edge of the main aftershock region, and the aftershock region subsequently extended about 5 km in the SE direction as defined by secondary aftershock activity. Enlargement of the aftershock region did not occur after the peak in aftershock activity, and the aftershock activity gradually declined. The distribution of hypocenters and seismogenic stress as defined by aftershocks suggest that the 2005 West Off Fukuoka Prefecture Earthquake occurred on the fault that is the NW extension of the Kego fault, which extends NW-SE through the Fukuoka metropolitan area, and that the largest aftershock occurred at the northwestern tip of the Kego fault.

show abstract

“…It is widely known that an ocean bottom seismometer (OBS) observation is essential to obtain a high-resolution aftershock distribution associated with large earthquakes that occurred in the marine environment (e.g., Shinohara et al, 2004;Sakai et al, 2005;Yamada et al, 2005). In addition, a spatially dense OBS observation is also necessary for a precise distribution of aftershocks occurring near a coast line be- cause a seismic network must cover a whole source region (Uehira et al, 2006;Yamada et al, 2008). Nine days after the mainshock, we started the aftershock observation using pop-up type OBSs in order to obtain detailed aftershock lateral and depth distributions of the 2007 Chuetsu-oki Earthquake.…”

Section: Introductionmentioning

confidence: 99%

Precise aftershock distribution of the 2007 Chuetsu-oki Earthquake obtained by using an ocean bottom seismometer network

et al. 2008

Self Cite

View full text Add to dashboard Cite

The Chuetsu-Oki Earthquake occurred on July 16, 2007. To understand the mechanism of earthquake generation, it is important to obtain a detailed seismic activity. Since the source region of the 2007 Chuetsu-oki Earthquake lies mainly offshore of Chuetsu region, a central part of Niigata Prefecture, it is difficult to estimate the geometry of faults using only the land seismic network data. A precise aftershock distribution is essential to determine the fault geometry of the mainshock. To obtain the detailed aftershock distribution of the 2007 Chuetsu-oki Earthquake, 32 Ocean Bottom Seismometers (OBSs) were deployed from July 25 to August 28 in and around the source region of the mainshock. In addition, a seismic survey using airguns and OBSs was carried out during the observation to obtain a seismic velocity structure below the observation area for precise hypocenter determination. Seven hundred and four aftershocks were recorded with high spatial resolution during the observation period using OBSs, temporally installed land seismic stations, and telemetered seismic land stations and were located using the double-difference method. Most of the aftershocks occurred in a depth range of 6-15 km, which corresponds to the 6-km/s layer. From the depth distribution of the hypocenters, the aftershocks occurred along a plane dipping to the southeast in the whole aftershock region. The dip angle of this plane is approximately 40• . This single plane with a dip to the southeast is considered to represent the fault plane of the mainshock. The regions where few aftershocks occurred are related to the asperities where large slip is estimated from the data of the mainshock. The OBS observation is indispensable to determine the precise depths of events which occur in offshore regions even close to a coast.

show abstract

Precise aftershock distribution of the 2005West Off Fukuoka Prefecture Earthquake (Mj=7.0) using a dense onshore and offshore seismic network

Cited by 22 publications

References 17 publications

Source rupture process of the 2016 central Tottori, Japan, earthquake (M JMA 6.6) inferred from strong motion waveforms

Source rupture process of the 2016 central Tottori, Japan, earthquake (M JMA 6.6) inferred from strong motion waveforms

Aftershock seismicity and fault structure of the 2005 West Off Fukuoka Prefecture Earthquake (MJMA7.0) derived from urgent joint observations

Precise aftershock distribution of the 2007 Chuetsu-oki Earthquake obtained by using an ocean bottom seismometer network

Contact Info

Product

Resources

About