Rupture Directivity Effect and Stress Heterogeneity of the 2013 Nantou Blind-Thrust Earthquakes, Taiwan

Wen, Yi-Ying; Yen, Yin-Tung; Irikura, Kojiro; Ching, Kuo En

doi:10.1785/0120140109

Cited by 13 publications

(10 citation statements)

References 29 publications

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“…The estimated stress drops are then about 0.3, 3.7, and 0.3 MPa, respectively. These values are slightly lower than those in previous studies (Wen et al 2014;Lee et al 2015;Ross & Ben-Zion 2016;Yagi et al 2016), but still within a reasonable range considering the large uncertainties in stress drop estimates. More importantly, the derived stress drops here have taken directivity into account and do not rely on corner frequency estimates that depend on azimuth and source models (Kaneko & Shearer 2015).…”

Section: Directivity Moment Tensor Inversion 1073contrasting

confidence: 51%

Toward automated directivity estimates in earthquake moment tensor inversion

Huang

Aso

Tsai

2017

Geophysical Journal International

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S U M M A R YRapid estimates of earthquake rupture properties are useful for both scientific characterization of earthquakes and emergency response to earthquake hazards. Rupture directivity is a particularly important property to constrain since seismic waves radiated in the direction of rupture can be greatly amplified, and even moderate magnitude earthquakes can sometimes cause serious damage. Knowing the directivity of earthquakes is important for ground shaking prediction and hazard mitigation, and is also useful for discriminating which nodal plane corresponds to the actual fault plane particularly when the event lacks aftershocks or outcropped fault traces. Here, we propose a 3-D multiple-time-window directivity inversion method through direct waveform fitting, with source time functions stretched for each station according to a given directivity. By grid searching for the directivity vector in 3-D space, this method determines not only horizontal but vertical directivity components, provides uncertainty estimates, and has the potential to be automated in real time. Synthetic tests show that the method is stable with respect to noise, picking errors, and site amplification, and is less sensitive to station coverage than other methods. Horizontal directivity can be properly recovered with a minimum azimuthal station coverage of 180 • , whereas vertical directivity requires better coverage to resolve. We apply the new method to the M w 6.0 Nantou, Taiwan earthquake, M w 7.0 Kumamoto, Japan earthquake, and M w 4.7 San Jacinto fault trifurcation (SJFT) earthquake in southern California. For the Nantou earthquake, we corroborate previous findings that the earthquake occurred on a shallow east-dipping fault plane rather than a west-dipping one. For the Kumamoto and SJFT earthquakes, the directivity results show good agreement with previous studies and demonstrate that the method captures the general rupture characteristics of large earthquakes involving multiple fault ruptures and applies to earthquakes with magnitudes as small as M w 4.7.

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Section: Directivity Moment Tensor Inversion 1073contrasting

confidence: 51%

Toward automated directivity estimates in earthquake moment tensor inversion

Huang

Aso

Tsai

2017

Geophysical Journal International

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“…M the suggestion of Wen et al (2014) that the high stress drop of these eight Nantou events might be related to an immature buried fault. Since these adopted slip models were inverted from different data sets with various techniques in a lower frequency range of 0.02-0.5 Hz, it might be better to derive the slip models with consistent analysis procedure for the further investigation and examination, such as relationship between the SMGA Fig.…”

Section: Discussionmentioning

confidence: 93%

“…Over the past several decades, source modeling with the empirical Green's function method (EGFM) (e.g., Irikura 1986;Miyake et al 2003;Kurahashi and Irikura 2010;Wen et al 2014;Yen et al 2014) has been applied frequently to explore the near-source characters and to simulate the broadband strong ground motions with a frequency range up to approximately 10 Hz. In this study, using the EGFM, we estimate the strong motion generation area (SMGA) and the stress drop by sequence.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Source characteristics of moderate-to-strong earthquakes in the Nantou area, Taiwan: insight from strong ground motion simulations

Wen

Chao

Yen³

et al. 2017

Earth Planets Space

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In Taiwan, the Nantou area is a seismically active region where several moderate events have occurred, causing some disasters during the past century. Here, we applied the strong ground motion simulation with the empirical Green's function method to investigate the source characteristics for the eight moderate blind-fault events that struck the Nantou area in 1999 and 2013. The results show that for these Nantou events, a high stress drop and focal depth dependence were noted, which might be related to the immature buried fault in this area. From the viewpoint of seismic hazard prevention and preparation, future earthquake scenarios that include high stress drop should be applied to more analyses, especially the moderate-to-large events originating from the immature blind faulting.

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“…5, we noticed that some northern stations (e.g., HWA001, HWA032, and HWA033) display clearly smaller amplitudes of later pluses for synthetics. The recent 2013 Nantou earthquakes were both thrust events showing different rupture directivity effects, which could be observed through the differences in the source spectral characteristics between stations located in the directions of the forward and backward ruptures (Wen et al 2014b). Figure 3 shows the source spectral ratios of the 2013 Ruisui mainshock to the EGF event.…”

Section: Application Of Broadband Waveformsmentioning

confidence: 99%

Hybrid Ground Motion Simulation for the 2013 ML 6.4 Ruisui, Taiwan Earthquake

Wen

Yen

Wen

et al. 2016

Terr. Atmos. Ocean. Sci.

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The 2013 M L 6.4 Ruisui earthquake struck a seismic gap around the northern part of the Longitudinal Valley where rare earthquakes have occurred for at least two decades. Seismic data with different frequency bands connote a diverse scale of source characteristics. The slip model derived by a previous study using long-period seismic data provided us with the preliminary earthquake source properties in low-frequency energy radiation. However, the high-frequency part of the seismic energy needs to be considered for the strong motions in the comprehensive frequency band. As a case study, we carried out broadband strong motion simulations through the hybrid scheme, which simulated waveforms combining the low-frequency motions (frequency-wavenumber integration method) and high-frequency motions (empirical Green's function method) to reveal the strong ground motion and source characteristics of the 2013 Ruisui earthquake. The results show that even though the local structure is complicated this hybrid simulation can effectively rebuild the overall broadband strong ground motion characteristics for the 2013 Ruisui earthquake. Additional study issues are required to better understand the nature of localized high peak ground acceleration and the related seismic hazards for future earthquakes.

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Rupture Directivity Effect and Stress Heterogeneity of the 2013 Nantou Blind-Thrust Earthquakes, Taiwan

Cited by 13 publications

References 29 publications

Toward automated directivity estimates in earthquake moment tensor inversion

Toward automated directivity estimates in earthquake moment tensor inversion

Source characteristics of moderate-to-strong earthquakes in the Nantou area, Taiwan: insight from strong ground motion simulations

Hybrid Ground Motion Simulation for the 2013 ML 6.4 Ruisui, Taiwan Earthquake

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