Source model composed of asperities for the 2003 Tokachi-oki, Japan, earthquake (M
                JMA
               = 8.0) estimated by the empirical Green’s function method

The source model of the 2011 Tohoku earthquake, which is composed of four strong motion generation areas (SMGAs), is estimated based on the broadband strong ground motion simulations in the frequency range 0.1-10 Hz using the empirical Green's function method. Two strong motion generation areas are identified in the Miyagioki region west of the hypocenter. Another two strong motion generation areas are located in the Fukushima-oki region southwest of the hypocenter. The strong ground motions in the frequency range 0.1-10 Hz along the Pacific coast are mainly controlled by these SMGAs. All the strong motion generation areas exist in the deeper portion of the source fault plane. The stress drops of the four SMGAs range from 6.6 to 27.8 MPa, which are similar to estimations for past M 7-class events occurring in this region. Compared with the slip models and aftershock distributions of past interplate earthquakes in the Miyagi-oki and Fukushima-oki regions since the 1930s, the SMGAs of the 2011 Tohoku earthquake spatially correspond to the asperities of M 7-class events in 1930s. In terms of broadband strong ground motions, the 2011 Tohoku earthquake is not only a tsunamigenic event with a huge coseismic slip near the trench but is also a complex event simultaneously rupturing pre-existing asperities.

Section: Introductionmentioning

confidence: 99%

Source model for strong ground motion generation in the frequency range 0.1–10 Hz during the 2011 Tohoku earthquake

Asano

Iwata

2012

“…Izutani (1998) examined the relationship between the amplitude of short-period source spectrum and the JMA magnitude for shallow earthquakes around Japan. He also compiled values of the stress-drop ratio assumed in the studies for earthquakes in and around Japan by Masui et al (1994), Harada et al (1995), Imanishi et al (1995), Kamae and Irikura (1995), and Tsurugi et al (1995) and obtained…”

Section: Discussionmentioning

confidence: 99%

“…Irikura (1986), Yokoi and Irikura (1991), and Irikura and Kamae (1994) introduced a parameter, the stress-drop ratio, into the EGF method to make a correction for the deviation from the similarity between a large and a small earthquake. Although the stress-drop ratio has been applied to the simulation of records for large earthquakes by using their aftershock records as empirical Green's functions (e.g., Masui et al, 1994;Harada et al, 1995;Imanishi et al, 1995;Kamae and Irikura, 1995;Tsurugi et al, 1995), it has not yet been clarified how we should assume the value of stressdrop ratio in synthesizing strong ground motion for future large earthquakes by the EGF method. Izutani (2005b) analyzed accelerograms observed at K-NET and KiK-net stations operated by the National Research Institute for Earth Science and Disaster Prevention, Japan (NIED) for earthquakes in the northwestern Kagoshima area, the western Tottori area, and the northern Miyagi area.…”

Section: Introductionmentioning

confidence: 99%

Scaling of short-period source spectrum for earthquakes in mid Niigata, Japan

Izutani

2007

Strong motion records at K-NET and KiK-net stations for earthquakes which occurred in the mid Niigata area are analyzed to examine the relationship between the amplitude of the short-period source spectrum and the seismic moment. Large earthquakes radiate more short-period seismic energy per unit seismic moment than small ones, which suggests a deviation from the similarity of earthquake source. Appropriate correction for the deviation from the similarity should be made when we synthesize strong ground motion for future large earthquakes by the empirical Green's function method.

“…This scaling relationship has been confirmed from more crustal earthquakes of either small or large magnitude (e.g., figure 7 of Suzuki and Iwata, 2006). Although some researchers have investigated the SMGAs of large subduction-zone interplate earthquakes, such as the 1994 Sanriku Haruka-Oki earthquake (Miyahara and Sasatani, 2004) and the 2003 Tokachi-Oki earthquake (Kamae and Kawabe, 2004), such studies are relatively few in comparison to the number carried out on crustal earthquakes. Suzuki and Iwata (2005) have estimated the SMGAs for moderate-sized interplate earthquakes that occurred at the subducting Pacific sea plate near Northeast Japan with a seismic moment ranging from 1.16 × 10 18 to 3.…”

Section: Introductionmentioning

confidence: 93%

“…1) was investigated by trial and error. Figure 17 shows the relationship between the combined size of SMGAs and the total seismic moment from the ten interplate earthquakes that we have analyzed and from the two large interplate events: the 1994 Sanriku Haruka-Oki earthquake (Miyahara and Sasatani, 2004) and the 2003 Tokachi-Oki earthquake (Kamae and Kawabe, 2004). The line is the self-similar relationship of the asperity size to the seismic moment for the crustal earthquakes obtained by Somerville et al (1999).…”

Section: Comparison With the 1978 Eventmentioning

confidence: 99%

Source model of the 2005 Miyagi-Oki, Japan, earthquake estimated from broadband strong motions

Suzuki

Iwata

2007

We estimate the source model of the 2005 Miyagi-Oki earthquake, which consists of two source patches called "strong motion generation areas (SMGAs)", to explain the broadband strong motions. The location of the first SMGA is determined from the arrival time differences between the first motion and the first pulse in the P-wave portion. Based on the broadband waveform modeling obtained using the empirical Green's function method, we estimate the parameters of the two SMGAs. The estimated location of the two SMGAs coincides with the two major large slip areas inferred from the inversion of strong-motion and teleseismic waveforms, which implies that the broadband strong motion of the 2005 Miyagi-Oki earthquake mainly radiates from the asperities. The deeper SMGA has a larger stress drop (34.1 MPa) than the shallower one (17.6 MPa). Comparison of the locations of SMGAs between the 2005 and 1978 Miyagi-Oki earthquakes suggests that they do not overlap with each other. The interplate earthquakes, including this event, were found to have smaller SMGAs than those predicted from the relationship of crustal earthquakes for a given seismic moment. This implies that the stress drop of the SMGAs for interplate earthquakes is larger than that for crustal earthquakes.