Double pincer movement: Encircling rupture splitting during the 2015 Mw 8.3 Illapel earthquake

Meng, Lingsen; Bao, Huang; Huang, Hui; Zhang, Ailin; Bloore, Andrew; Liu, Zhipeng

doi:10.1016/j.epsl.2018.04.057

Cited by 31 publications

(54 citation statements)

References 51 publications

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“…McFadden et al 1986) was used to enhance the signalto-noise ratio of the image, and the data were filtered in the 0. the kinematic BP and HBP methods. The source models of the 2015 Illapel earthquake showed a complex rupture evolution along both the up-dip and down-dip directions (Melgar et al 2016;An et al 2017;Yin et al 2018;Meng et al 2018), which is more consistent with the image obtained by the kinematic BP and HBP methods. The increased signal in the shallow part should reflect the source of high-frequency radiation from the up-dip rupture propagation.…”

Section: Application To the Real Datasupporting

confidence: 74%

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Backprojection to image slip

Okuwaki¹,

Kasahara²,

Yagi³

et al. 2018

Preprint

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SUMMARYWaveform backprojection is a key technique of earthquake-source imaging, which has been widely used for extracting information of earthquake source evolution that cannot be obtained by kinematic source inversion. The technique enjoys considerable popularity, owing to the simplicity of its implementation and the robustness of its processing, but the physical meaning of backprojection images has remained elusive. In this study, we reviewed the mathematical representation of backprojection (BP) and hybrid backprojection (HBP) methods, following the pioneering work of Fukahata et al. (Geophys. J. Int. (2014) 196, 552-559), to clarify the physical implications of BP images. We found that signal intensity in BP and HBP images is scaled with the amplitude of the Green's function that corresponds to a unit-step slip, which results in the signal intensity being depth dependent. We propose variants of BP and HBP, which we call kinematic BP and HBP, 2 R. Okuwaki, A. Kasahara, Y. Yagi, S. Hirano, and Y. Fukahata respectively, to relate the BP signal intensity to slip motion of an earthquake by modifying the normalizing factors used in the original BP and HBP methods. The original BP and HBP images remain useful for assessing the spatiotemporal strength of the wave radiation, which scales with the amplitude of the Green's function, whereas the kinematic BP and HBP methods are suitable for imaging the slip motion that is responsible for the high-frequency radiation produced during the source-rupture process.

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Section: Application To the Real Datasupporting

confidence: 74%

“…M W 9.0 2011 Tohoku-oki, Japan and M W 8.3 2015 Illapel, Chile, earthquakes;Meng et al 2011;Melgar et al 2016;Meng et al 2018), it is plausible that there exist kinematic features around the rupture tip or the healing front (e.g. Madariaga et al 2006) even at shallow.…”

Section: Introductionmentioning

confidence: 99%

Backprojection to image slip

Okuwaki¹,

Kasahara²,

Yagi³

et al. 2018

Preprint

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“…Here, in addition to the hypocenter correction, we also applied a slowness correction that accounts for the spatial derivatives of the travel times in the source region. The SEBP reduces the spatial bias and improves the consistency between BP using different arrays (Bao et al, 2019;Meng et al, 2016;Meng et al, 2018). The slowness correction term can be inferred using the relocated locations of aftershocks.…”

Section: Bp Of the Coseismic Rupture Processmentioning

confidence: 99%

Nucleation and Kinematic Rupture of the 2017 Mw 8.2 Tehuantepec Earthquake

Meng

Huang

Xie

et al. 2019

Geophysical Research Letters

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Integrated observations from the 2017 Mw 8.2 Tehuantepec, Mexico, earthquake probe one of the largest normal‐faulting events inside a subducting slab. In this study, we utilize a template matching approach to detect possible missing earthquakes within a 2‐month period before the mainshock. The seismicity rate shows an abrupt increase in the last day around the mainshock hypocenter. The large distance between most of the foreshocks and the mainshock is not consistent with static stress triggering but suggests alternative mechanisms such as delayed dynamic triggering or aseismic transients. Back‐projection using the USArray network reveals that the rupture propagated northwestward unilaterally at a speed of 3.6 km/s and terminated north of the Tehuantepec Ridge. Towards the end of the rupture, a wide step‐over occurred onto an adjacent fault parallel to the main fault plane. The mainshock is likely a reactivation of subducted outer‐rise faults, supported by the similarity of fault‐strike angles. The surprisingly large magnitude is consistent with exceedingly large dimensions of outer‐rise faulting in this segment of the central Mexican trench.

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“…Similarly, Chen et al () study two deep earthquakes ( M > 5) near the 2015 M w 7.9 Bonin earthquake and estimate the spatial error around 15 km. Besides, Meng et al () perform the slowness‐enhanced BP based on the aftershocks of 2015 M w 8.3 Illapel earthquake and reduce the spatial error from 24 to 8 km. Here we consider that HFR location error and therefore R hf error are on the order of 20 km, which is reasonably small comparing to the dimension of megathrust events ( M > 7) and the gaps between HF and LF sources.…”

Section: High‐frequency Distance Metricmentioning

confidence: 99%

A High‐Frequency Distance Metric in Ground‐Motion Prediction Equations Based on Seismic Array Backprojections

Feng

Meng

2018

Geophysical Research Letters

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Typical ground‐motion prediction equations (GMPEs) measure source‐to‐site distances relative to the closest point on the rupture plane (Rrup). However, for megathrust earthquakes (Mw > 8), the oversimplification of the earthquake source characteristics in distance metrics results in significant bias. Recent studies suggest that the high‐frequency (HF) and low‐frequency (LF) energy tend to emanate from different portions of the megathrusts. This phenomenon motivates an alternative distance metric based on the array backprojection imaging technique that effectively captures regions releasing HF energy. Herein, we define an HF distance metric (Rhf) as the distance from the site to the high‐frequency radiation zone. We study five Mw > 7.2 megathrust earthquakes in Japan and Chile and find that Rhf outperforms Rrup in predicting the ground shaking intensity between 0.5 and 4 Hz. We consider Rhf as a complementary measure to conventional GMPE distance metrics and a more accurate ground‐motion predictor in many cases.

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Double pincer movement: Encircling rupture splitting during the 2015 Mw 8.3 Illapel earthquake

Cited by 31 publications

References 51 publications

Backprojection to image slip

Backprojection to image slip

Nucleation and Kinematic Rupture of the 2017 Mw 8.2 Tehuantepec Earthquake

A High‐Frequency Distance Metric in Ground‐Motion Prediction Equations Based on Seismic Array Backprojections

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