Seismic characteristics of supershear and sub‐Rayleigh earthquakes: Implication from simple cases

Zhang, Zhenguo; Xu, Jiankuan; Huang, Hanqing; Chen, Xiaofei

doi:10.1002/2017gl074158

Cited by 10 publications

(6 citation statements)

References 32 publications

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“…Similar Mach front attenuation in 3D setups was observed in Ref. [52] and reduced ground motion amplitude was shown to occur near the free-surface of simulated supershear earthquakes [53]. Additionally, once the finite-thickness of the plates is taken into account, our simulations show that the limiting rupture speed is larger than the plane-stress approximation.…”

Section: Discussionsupporting

confidence: 82%

Dynamic fields at the tip of sub-Rayleigh and supershear frictional rupture fronts

Svetlizky

Albertini

Cohen

et al. 2020

Journal of the Mechanics and Physics of Solids

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The onset of frictional motion at the interface between two distinct bodies in contact is characterized by the propagation of dynamic rupture fronts. We combine friction experiments and numerical simulations to study the properties of these frictional rupture fronts. We extend previous analysis of slow and sub-Rayleigh rupture fronts and show that strain fields and the evolution of real contact area in the tip vicinity of supershear ruptures are well described by analytical fracture-mechanics solutions. Fracture-mechanics theory further allows us to determine long sought-after interface properties, such as local fracture energy and frictional peak strength. Both properties are observed to be roughly independent of rupture speed and mode of propagation. However, our study also reveals discrepancies between measurements and analytical solutions that appear as the rupture speed approaches the longitudinal wave speed. Further comparison with dynamic simulations illustrates that, in the supershear propagation regime, transient and geometrical (finite sample thickness) effects cause smaller near-tip strain amplitudes than expected from the fracturemechanics theory. By showing good quantitative agreement between experiments, simulations and theory over the entire range of possible rupture speeds, we demonstrate that frictional rupture fronts are classic dynamic cracks despite residual friction.

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Section: Discussionsupporting

confidence: 82%

Dynamic fields at the tip of sub-Rayleigh and supershear frictional rupture fronts

Svetlizky

Albertini

Cohen

et al. 2020

Journal of the Mechanics and Physics of Solids

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“…The surface traces of these faults are typically linear, continuous, and narrow, as evidenced by the optical satellite images [50], suggesting that stress-strength of the fault plane is mechanically homogeneous. What is more, supershear events tend to show a "quiet" aftershock potential, as revealed by both numerical simulations [51] and aftershock observations [49,52]. By contrast, aftershocks are likely to cluster on the secondary structures off the fault plane [52].…”

Section: An Early Supershear Rupture Of the Palu Earthquakementioning

confidence: 85%

“…Bouchon and Karabulut [52] also emphasized that friction is relatively uniform over the supershear segments deduced by the post-earthquake quiescence of the fault. As for the seismic hazard analysis of supershear ruptures, Zhang et al [51] reported that the supershear earthquake will bring in more strong shaking at large distance to the fault plane rather than intensive near-fault field ground motion, attributable to (1) the generation of S-wave Mach front, which can persist farther distance and (2) the seismic energy transmitted further with large amplitudes, which will definitely exacerbate the hazard [2,53,54].…”

Section: An Early Supershear Rupture Of the Palu Earthquakementioning

confidence: 99%

The 2018 Mw 7.5 Palu Earthquake: A Supershear Rupture Event Constrained by InSAR and Broadband Regional Seismograms

Fang

Wen

et al. 2019

Remote Sensing

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The 28 September 2018 Mw 7.5 Palu earthquake occurred at a triple junction zone where the Philippine Sea, Australian, and Sunda plates are convergent. Here, we utilized Advanced Land Observing Satellite-2 (ALOS-2) interferometry synthetic aperture radar (InSAR) data together with broadband regional seismograms to investigate the source geometry and rupture kinematics of this earthquake. Results showed that the 2018 Palu earthquake ruptured a fault plane with a relatively steep dip angle of ~85°. The preferred rupture model demonstrated that the earthquake was a supershear event from early on, with an average rupture speed of 4.1 km/s, which is different from the common supershear events that typically show an initial subshear rupture. The rupture expanded rapidly (~4.1 km/s) from the hypocenter and propagated bilaterally towards the north and south along the strike direction during the first 8 s, and then to the south. Four visible asperities were ruptured during the slip pulse propagation, which resulted in four significant deformation lobes in the coseismic interferogram. The maximum slip of 6.5 m was observed to the south of the city of Palu, and the total seismic moment released within 40 s was 2.64 × 1020 N·m, which was equivalent to Mw 7.55. Our results shed some light on the transtensional tectonism in Sulawesi, given that the 2018 Palu earthquake was dominated by left-lateral strike slip (slip maxima is 6.2 m) and that some significant normal faulting components (slip maxima is ~3 m) were resolved as well.

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“…Although sustained supershear ruptures exist on both fault steps, the area with a sub‐Rayleigh rupture speed is larger on the extensional step with the 1.5 km step width (Hu, Xu, et al, ). Zhang et al () noticed that the near‐field ground motion associated with a free‐surface‐induced supershear rupture is smaller than that associated with a sub‐Rayleigh rupture. According to our study, sub‐Rayleigh ruptures may generate stronger horizontal PGV values close to strike‐slip fault segments.…”

Section: Numerical Resultsmentioning

confidence: 99%

High Frequency Near‐Field Ground Motion Excited by Strike‐Slip Step Overs

Wen

Chen

2018

JGR Solid Earth

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We performed dynamic rupture simulations on step overs with 1–2 km step widths and present their corresponding horizontal peak ground velocity distributions in the near field within different frequency ranges. The rupture speeds on fault segments are determinant in controlling the near‐field ground motion. A Mach wave impact area at the free surface, which can be inferred from the distribution of the ratio of the maximum fault‐strike particle velocity to the maximum fault‐normal particle velocity, is generated in the near field with sustained supershear ruptures on fault segments, and the Mach wave impact area cannot be detected with unsustained supershear ruptures alone. Sub‐Rayleigh ruptures produce stronger ground motions beyond the end of fault segments. The existence of a low‐velocity layer close to the free surface generates large amounts of high‐frequency seismic radiation at step over discontinuities. For near‐vertical step overs, normal stress perturbations on the primary fault caused by dipping structures affect the rupture speed transition, which further determines the distribution of the near‐field ground motion. The presence of an extensional linking fault enhances the near‐field ground motion in the extensional regime. This work helps us understand the characteristics of high‐frequency seismic radiation in the vicinities of step overs and provides useful insights for interpreting the rupture speed distributions derived from the characteristics of near‐field ground motion.

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Seismic characteristics of supershear and sub‐Rayleigh earthquakes: Implication from simple cases

Cited by 10 publications

References 32 publications

Dynamic fields at the tip of sub-Rayleigh and supershear frictional rupture fronts

Dynamic fields at the tip of sub-Rayleigh and supershear frictional rupture fronts

The 2018 Mw 7.5 Palu Earthquake: A Supershear Rupture Event Constrained by InSAR and Broadband Regional Seismograms

High Frequency Near‐Field Ground Motion Excited by Strike‐Slip Step Overs

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