Rupture directivity, stress drop, and hypocenter migration of small earthquakes in the Yamagata-Fukushima border swarm triggered by upward pore-pressure migration after the 2011 Tohoku-Oki earthquake

Yoshida, Keisuke; Saito, Tatsuhiko; Emoto, Kentaro; Urata, Yumi; Sato, D.

doi:10.1016/j.tecto.2019.228184

Cited by 18 publications

(16 citation statements)

References 55 publications

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“…4b). Recent observations of rupture directivity in small earthquakes also suggest that propagation directions have preferred directions affected by material properties (Kane et al 2013) and by states of stress and fault strength (Folesky et al 2016;Yoshida et al 2019a).…”

Section: Discussionmentioning

confidence: 99%

“…For estimation of rupture directivity and stress drop, a method similar to Yoshida et al (2019a) was used as detailed in "A generalized rupture model" section. Under this approach, the durations of apparent moment rate functions (AMRFs) were inverted for rupture parameters.…”

Section: Methodsmentioning

confidence: 99%

“…The dominant frequency of the waveform is used for the estimation of stress drop based on simple symmetrical circular source models (Brune 1970;Sato and Hirasawa 1973;Madariaga 1976). However, if the real source process is asymmetrical or has a significant directivity, the assumption of symmetrical rupture evolution can lead to a large error in the estimated stress drop (Kaneko and Shearer 2015;Yoshida et al 2019a). It has been reported that a significant proportion of large earthquake ruptures are predominantly unilateral (McGuire et al 2002).…”

Section: Introductionmentioning

confidence: 99%

“…It has been reported that a significant proportion of large earthquake ruptures are predominantly unilateral (McGuire et al 2002). Recently, directivity effects have been observed in seismic waves for moderate-sized (e.g., Abercrombie et al 2017;Boatwright 2007;McGuire 2004) and even smaller earthquakes (e.g., Kane et al 2013;Folesky et al 2016;Yamada et al 2005;Yoshida et al 2019a). Rupture directivity is of interest itself, but is also important for unbiased estimation of other geophysical parameters, including stress drop.…”

Section: Introductionmentioning

confidence: 99%

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Prevalence of asymmetrical rupture in small earthquakes and its effect on the estimation of stress drop: a systematic investigation in inland Japan

Yoshida

2019

Geosci. Lett.

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Stress drops of small earthquakes have been estimated under the assumption that the rupture propagates symmetrically within a circular fault. However, recent studies have observed directivity effects on seismic waves even for small earthquakes. In this study, rupture directivity was investigated systematically for small-to-moderate-sized earthquakes (M 3.5-5.5) that occurred beneath inland Japan from 2004 to April 2019. Apparent moment rate functions were determined for 1463 earthquakes, and their corner frequencies were inverted for their rupture parameters. The results indicate that most of the analyzed earthquakes (1217 of 1463) are characterized by significantly asymmetrical rupture propagation. The stress drops of the earthquakes estimated by considering asymmetrical rupture propagation were 16.8 MPa, which are almost twice the estimates based on the commonly used symmetrical rupture model. This shows the importance of recognizing the diversity of ruptures, even for small earthquakes, for extracting information about earthquake sources and the Earth's structure. The prevailing rupture directivity can provide useful information on source parameters including the fault size, fault geometry, and rupture velocity of small earthquakes.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prevalence of asymmetrical rupture in small earthquakes and its effect on the estimation of stress drop: a systematic investigation in inland Japan

Yoshida

2019

Geosci. Lett.

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“…We used the amplitudes of direct P and S waves (corrected by those of a reference earthquake whose focal mechanism was known) to calculate the focal mechanisms. We followed the procedure outlined in Yoshida, Saito, et al (2019), which utilizes the amplitude ratios of P, SH, and SV waves by assuming that the medium in the vicinity of the source is homogeneous and isotropic (Dahm, 1996). We limited the distance between target and reference events to less than 3 km.…”

Section: Methodsmentioning

confidence: 99%

Stress Release Process Along an Intraplate Fault Analogous to the Plate Boundary: A Case Study of the 2017 M5.2 Akita‐Daisen Earthquake, NE Japan

et al. 2020

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Stress accumulation and release inside the plate remains poorly understood compared to that at the plate boundaries. Spatiotemporal variations in foreshock and aftershock activities can provide key constraints on time‐dependent stress and deformation processes inside the plate. The 2017 M5.2 Akita‐Daisen intraplate earthquake in NE Japan was preceded by intense foreshock activity and triggered a strong sequence of aftershocks. We examine the spatiotemporal distributions of foreshocks and aftershocks and determine the coseismic slip distribution of the mainshock. Our results indicate that seismicity both before and after the mainshock was concentrated on a planar structure with N‐S strike that dips steeply eastward. We observe a migration of foreshocks toward the mainshock rupture area, suggesting the possibility that foreshocks were triggered by aseismic phenomena preceding the mainshock rupture. The mainshock rupture propagated toward the north, showing less slip beneath foreshock regions. The stress drop of the mainshock was 1.4 MPa, and the radiation efficiency was 0.72. Aftershocks were intensely triggered near the edge of large coseismic slip regions where shear stress increased. The aftershock region expanded along the fault strike, which can be attributed to the postseismic aseismic slip of the mainshock. We find that the foreshocks, mainshock, aftershocks, and postseismic slip released stress at different segments along the fault, which may reflect differences in frictional properties. Obtained results were similar to those observed for interplate earthquakes, which supports the hypothesis that the deformation processes along plate boundaries and intraplate faults are fundamentally the same.

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Empirical Green’s function analysis of some induced earthquake pairs from the Groningen gas field

Oates,

Schmitz,

Zurek

et al. 2024

J Seismol

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We have applied the empirical Green’s function (EGF) method to 53 pairs of earthquakes, with magnitudes ranging from M = 0.4 to M = 3.4, induced by gas production from the Groningen field in the Netherlands. For a subset of the events processed, we find that the relative source time functions obtained by the EGF deconvolution show clear indications of a horizontal component of rupture propagation. The earthquake monitoring network used has dense azimuthal coverage for nearly all events such that wavelet duration times can be picked as a function of source-station azimuth and inverted using the usual Doppler broadening model to estimate rupture propagation strike, distance, and velocity. Average slip velocities have also been estimated and found to be in agreement with typical published values. We have used synthetic data, from both a simple convolutional model of the seismogram and more sophisticated finite difference rupture simulations, to validate our data processing workflow and develop kinematic models which can explain the observed characteristics of the field data. Using a measure based on the L1-norm to discriminate results of differing quality, we find that the highest quality results show very good alignment of the rupture propagation with directions of the detailed fault map, obtained from the full-field 3D seismic data. The dip direction rupture extents were estimated from the horizontal rupture propagation distances and catalogue magnitudes showing that, for all but the largest magnitude event (the M = 3.4 event of 8th January 2018), the dip-direction extent is sufficiently small to be contained wholly within the reservoir.

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Rupture directivity, stress drop, and hypocenter migration of small earthquakes in the Yamagata-Fukushima border swarm triggered by upward pore-pressure migration after the 2011 Tohoku-Oki earthquake

Cited by 18 publications

References 55 publications

Prevalence of asymmetrical rupture in small earthquakes and its effect on the estimation of stress drop: a systematic investigation in inland Japan

Prevalence of asymmetrical rupture in small earthquakes and its effect on the estimation of stress drop: a systematic investigation in inland Japan

Stress Release Process Along an Intraplate Fault Analogous to the Plate Boundary: A Case Study of the 2017 M5.2 Akita‐Daisen Earthquake, NE Japan

Empirical Green’s function analysis of some induced earthquake pairs from the Groningen gas field

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