Sources of shaking and flooding during the Tohoku-Oki earthquake: A mixture of rupture styles

Wei, Shengji; Helmberger, Donald V.; Avouac, Jean Philippe; Jiang, Junle

doi:10.1016/j.epsl.2012.04.006

Cited by 130 publications

(165 citation statements)

References 41 publications

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“…Both the spatial extent and rupture history are consistent with the results of high-frequency teleseismic back projection (e.g., Ishii, 2011;Koper et al, 2011;Meng et al, 2011;Yao et al, 2011;Zhang et al, 2011). The along-strike rupture length is approximately 300 km, smaller than that of the low-frequency slip inversion (e.g., Wei et al, 2012) but consistent with the spatial extent of the source model from the high-frequency strong-motion data (Asano and Iwata, 2012). The southward rupture extent and directivity adequately explain the observed strong ground accelerations in the Kanto area.…”

Section: Methodssupporting

confidence: 71%

Application of Seismic Array Processing to Earthquake Early Warning

Meng¹,

Allen²,

Ampuero³

2014

Bulletin of the Seismological Society of America

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Earthquake early warning (EEW) systems that issue warnings prior to the arrival of strong shaking are essential in mitigating earthquake hazard. Currently operating EEW systems work on point-source assumptions and are of limited effectiveness for large events, for which ignoring finite-source effects result in magnitude underestimation. Here, we explore the concept of characterizing rupture dimensions in real time for EEW using small-aperture seismic arrays located near active faults. Back tracing array waveforms allow estimation of the extent of the rupture front (as a proxy of the rupture size) and directivity in real time, providing complementary EEW capabilities for M > 7 earthquakes to existing EEW systems. We implement it in a simulated realtime environment and analyze the 2004 M 6 Parkfield, California, earthquake recordings by the U.S. Geological Survey Parkfield dense Seismograph ARray (UPSAR) array and the 2010 M 7.2 El Mayor-Cucapah earthquake recordings by strong-motion sensors in San Diego, California. We find it important to correct for the bias in back azimuth induced by dipping structures beneath the UPSAR array, based on data from smaller events. Our estimated rupture length is 30% shorter than those inferred from other studies but still reasonable for EEW purposes. We attribute this difference to rupture directivity effects and the limited field of view of a single array. The accuracy of the approach may be improved with a network of arrays with overlapping fields of view. We demonstrate this by tracking the 2011 Tohoku earthquake rupture with two clusters of Hi-net stations in Kyushu and northern Hokkaido. The obtained results are consistent with teleseismic back-projection results and yield reasonable estimates of rupture length and directivity. Compared with other proposed finite-fault EEW approaches, the array method is less affected by the coarseness of a Global Positioning System or seismic network and provides a high-frequency characterization of the rupture that yields more suitable predictors of ground shaking for certain structures.

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Section: Methodssupporting

confidence: 71%

Application of Seismic Array Processing to Earthquake Early Warning

Meng¹,

Allen²,

Ampuero³

2014

Bulletin of the Seismological Society of America

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“…We find that this effect is significant for time-domain stacking but can be efficiently mitigated by MUSIC array processing with a reference window strategy. MUSIC back-projection of the Tohoku-Oki earthquake recordings at the USArray and European array show no significant tendency for the source (Wei et al, 2012). The beamforming results are dominated by the artifact at periods longer than 4 s. The MUSIC results are consistent over all frequency bands.…”

Section: Summary and Discussionsupporting

confidence: 69%

Mitigating artifacts in back-projection source imaging with implications for frequency-dependent properties of the Tohoku-Oki earthquake

et al. 2012

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Comparing teleseismic array back-projection source images of the 2011 Tohoku-Oki earthquake with results from static and kinematic finite source inversions has revealed little overlap between the regions of high-and low-frequency slip. Motivated by this interesting observation, back-projection studies extended to intermediate frequencies, down to about 0.1 Hz, have suggested that a progressive transition of rupture properties as a function of frequency is observable. Here, by adapting the concept of array response function to non-stationary signals, we demonstrate that the "swimming artifact", a systematic drift resulting from signal non-stationarity, induces significant bias on beamforming back-projection at low frequencies. We introduce a "reference window strategy" into the multitaper-MUSIC back-projection technique and significantly mitigate the "swimming artifact" at high frequencies (1 s to 4 s). At lower frequencies, this modification yields notable, but significantly smaller, artifacts than time-domain stacking. We perform extensive synthetic tests that include a 3D regional velocity model for Japan. We analyze the recordings of the Tohoku-Oki earthquake at the USArray and at the European array at periods from 1 s to 16 s. The migration of the source location as a function of period, regardless of the backprojection methods, has characteristics that are consistent with the expected effect of the "swimming artifact". In particular, the apparent up-dip migration as a function of frequency obtained with the USArray can be explained by the "swimming artifact". This indicates that the most substantial frequency-dependence of the Tohoku-Oki earthquake source occurs at periods longer than 16 s. Thus, low-frequency back-projection needs to be further tested and validated in order to contribute to the characterization of frequency-dependent rupture properties.

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“…Another striking feature is the distinct location of high-frequency (HF) and low-frequency (LF) slip. Teleseismic back-projection studies find that the HF energy around 1 Hz originates from the deeper region (Kanamori and Yomogida, 2011;Meng et al, 2011;Yao et al, 2011), while other studies point to the low-frequency radiation coming from the shallower region (Simons et al, 2011;Wei et al, 2012). The present work aims to provide a dynamic interpretation of the contrasted frequency content of slip in the deeper and shallower regions of the Tohoku-Oki earthquake rupture.…”

Section: Introductionmentioning

confidence: 99%

A dynamic model of the frequency-dependent rupture process of the 2011 Tohoku-Oki earthquake

2012

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We present a 2D dynamic rupture model that provides a physical interpretation of the key features of the 2011 Tohoku-Oki earthquake rupture. This minimalistic model assumes linear slip-weakening friction, the presence of deep asperities and depth-dependent initial stresses. It reproduces the first-order observations of the alongdip rupture process during its initial 100 s, such as large static slip and low-frequency radiation up-dip from the hypocenter, and slow rupture punctuated by high-frequency radiation in deeper regions. We also derive quantitative constraints on the ratio of shallow versus deep radiation from teleseismic back-projection source imaging. This ratio is explained in our model by the rupture of deep asperities surrounded by low stress drop regions, and by the decrease of initial stresses towards the trench.

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Sources of shaking and flooding during the Tohoku-Oki earthquake: A mixture of rupture styles

Cited by 130 publications

References 41 publications

Application of Seismic Array Processing to Earthquake Early Warning

Application of Seismic Array Processing to Earthquake Early Warning

Mitigating artifacts in back-projection source imaging with implications for frequency-dependent properties of the Tohoku-Oki earthquake

A dynamic model of the frequency-dependent rupture process of the 2011 Tohoku-Oki earthquake

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