Compound fault rupture during the 2004 off the Kii Peninsula earthquake (M 7.4) inferred from highly resolved coseismic sea-surface deformation

Baba, Toshitaka; Cummins, Phil R.; Hori, Takane

doi:10.1186/bf03351810

Cited by 47 publications

(40 citation statements)

References 21 publications

(27 reference statements)

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“…Another group proposes that the mainshock occurred on a NW-SE striking reverse fault extending between the trough axis and the forearc basin and dipping to the southwest. This model is based on the aftershock distribution corresponding to cluster A and the initial seawater uplift estimated from tsunami observations (e.g., Yamanaka 2004;Baba et al 2005;Matsumoto and Mikada 2005;Saito et al 2010), although the reverse fault of this model is in conflict with the CMT solution.…”

Section: Discussionmentioning

confidence: 99%

“…Some researchers consider that this event was a composite of movements on both a dip-slip fault below the trough axis and a strike-slip fault below the Kumano forearc basin (e.g., Yagi 2004;Satake et al 2005;Hara 2005). Other researchers have proposed a model in which the mainshock ruptured a reverse fault below the forearc basin (e.g., Yamanaka 2004;Baba et al 2005;Matsumoto and Mikada. 2005;Saito et al 2010).…”

Section: Introductionmentioning

confidence: 99%

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Seismic activity beneath the Nankai trough revealed by DONET ocean-bottom observations

2013

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We conducted a detailed investigation of seismic activity from January 2011 to February 2013 along the Nankai trough off the Kii Peninsula, central Japan, by using data obtained from the DONET ocean-bottom observation network. The hypocenters are mostly within the subducting Philippine Sea (PHS) plate, although a few are along the plate boundary or in the sedimentary wedge below the Kumano forearc basin. The seismic activity can be separated into events above and below 20 km depth, which corresponds approximately to the Moho. The hypocenter distributions are distinctly different for these groups. The seismic activity in the oceanic crust can be further separated into three clusters. Most of the seismic activity recorded in our data represents aftershocks of the 2004 off the Kii Peninsula earthquakes (M JMA = 7.1, 7.4, and 6.5), which occurred in the PHS plate. The hypocenter distribution in the oceanic crust correlates well with the location of the Paleo-Zenisu ridge, which is formed by a chain of seamounts that is subducting beneath the forearc basin. The hypocenters in the uppermost mantle are aligned on a plane dipping to the southeast, consistent with the existence of a thrust fault cutting through the lithosphere of the oceanic plate. The focal mechanisms of the earthquakes show that the axis of compressive stress in the PHS plate is oriented N-S, almost perpendicular to the direction of plate convergence, indicating a complex tectonic regime in this region. These results suggest that intraplate shortening may be occurring in the subducting oceanic plate.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Seismic activity beneath the Nankai trough revealed by DONET ocean-bottom observations

2013

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“…Without a smoothing constraint, the result of the tsunami waveform inversion might be bumpy and non-physical, especially for cases with high spatial resolution (Wu and Ho, 2011). In other studies on tsunami waveform inversion by Baba et al (2005) and Wu and Ho (2011), an equality constraint was imposed to maintain the smoothness of the inverted parameters to satisfy the long wave assumption, while by Saito et al (2010) and Gusman et al (2010) Figure 8. Scatter plots of each inversion method with respect to the waveforms of the target source at all gauges.…”

Section: Resultsmentioning

confidence: 99%

“…The basic premise is to replace the fault model by an auxiliary basis function on unit sources, which is equivalent to the sub-fault approach by Satake (1987). For instances, Baba et al (2005) used a simplified fault model by disregarding actual earthquake parameters to produce the initial profile on each unit source, whereas Satake et al (2005) proposed a more direct approximation using a pyramidal shape with a flat top. Other studies by Liu and Wang (2008) and Saito et al (2010) demonstrated attempts to use Gaussian function, whereas Wu and Ho (2011) adopted a top-hat small unit source to represent the initial profile.…”

Section: Introductionmentioning

confidence: 99%

Randomly distributed unit sources to enhance optimization in tsunami waveform inversion

Mulia

Asano

2015

Nat. Hazards Earth Syst. Sci.

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Abstract. In tsunami waveform inversion using the conventional Green's function technique, an optimal solution is sometimes difficult to obtain because of various factors. This study proposes a new method to both optimize the determination of the unknown parameters and introduce a global optimization method for tsunami waveform inversion. We utilize a genetic algorithm that further enhanced by a pattern search method to find an optimal distribution of unit source locations prior to the inversion. Unlike the conventional method that characterized by equidistant unit sources, our method generates a random spatial distribution of unit sources inside the inverse region. This leads to a better approximation of the initial profile of a tsunami. The method has been tested using an artificial tsunami source with real bathymetry data. Comparison results demonstrate that the proposed method has considerably outperformed the conventional one in terms of model accuracy.

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“…His method was further used on the tsunami forecast (Wei et al, 2003;Yamazaki et al, 2005) and exploration of earthquake events with sea surface deformation (Pires and Miranda 2001;Baba et al, 2002Baba et al, , 2005Satake et al, 2005;Piatanesi and Lorito 2007). However, those implementations used very large unit sources such that the details of the tsunami profiles could not be described.…”

Section: Introductionmentioning

confidence: 99%

High resolution tsunami inversion for 2010 Chile earthquake

2011

Nat. Hazards Earth Syst. Sci.

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Abstract. We investigate the feasibility of inverting highresolution vertical seafloor displacement from tsunami waveforms. An inversion method named "SUTIM" (small unit tsunami inversion method) is developed to meet this goal. In addition to utilizing the conventional least-square inversion, this paper also enhances the inversion resolution by Grid-Shifting method. A smooth constraint is adopted to gain stability. After a series of validation and performance tests, SUTIM is used to study the 2010 Chile earthquake. Based upon data quality and azimuthal distribution, we select tsunami waveforms from 6 GLOSS stations and 1 DART buoy record. In total, 157 sub-faults are utilized for the highresolution inversion. The resolution reaches 10 sub-faults per wavelength. The result is compared with the distribution of the aftershocks and waveforms at each gauge location with very good agreement. The inversion result shows that the source profile features a non-uniform distribution of the seafloor displacement. The highly elevated vertical seafloor is mainly concentrated in two areas: one is located in the northern part of the epicentre, between 34 • S and 36 • S; the other is in the southern part, between 37 • S and 38 • S.

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Compound fault rupture during the 2004 off the Kii Peninsula earthquake (M 7.4) inferred from highly resolved coseismic sea-surface deformation

Cited by 47 publications

References 21 publications

Seismic activity beneath the Nankai trough revealed by DONET ocean-bottom observations

Seismic activity beneath the Nankai trough revealed by DONET ocean-bottom observations

Randomly distributed unit sources to enhance optimization in tsunami waveform inversion

High resolution tsunami inversion for 2010 Chile earthquake

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