A Discussion of the Depth Extent of Rupture in Large Continental Earthquakes

Strehlau, Jurgen

doi:10.1029/gm037p0131

Cited by 50 publications

(14 citation statements)

References 71 publications

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“…Similarities between earthquake depth frequency distributions and predicted yield strength envelopes have been interpreted for several decades to indicate that the seismic‐aseismic transition is governed by the gradual onset of temperature and strain rate‐dependent ductile deformation mechanisms of rocks [e.g., Chen and Molnar , ; Meissner and Strehlau , ; Scholz , ; Sibson , ; Strehlau , ]. In this model, earthquake nucleation and stress drop peak close to the bottom of the brittle unstable domain.…”

Section: Discussionmentioning

confidence: 99%

Structural heterogeneity of the midcrust adjacent to the central Alpine Fault, New Zealand: Inferences from seismic tomography and seismicity between Harihari and Ross

Bourguignon

Bannister

Henderson

et al. 2015

Geochem Geophys Geosyst

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Determining the rates and distributions of microseismicity near major faults at different points in the seismic cycle is a crucial step toward understanding plate boundary seismogenesis. We analyze data from temporary seismic arrays spanning the central section of the Alpine Fault, New Zealand, using doubledifference seismic tomography. This portion of the fault last ruptured in a large earthquake in 1717 AD and is now late in its typical 330 year cycle of Mw8 earthquakes. Seismicity varies systematically with distance from the Alpine Fault: (1) directly beneath the fault trace, earthquakes are sparse and largely confined to the footwall at depths of 4-11 km; (2) at distances of 0-9 km southeast of the trace, seismicity is similarly sparse and shallower than 8 km; (3) at distances of 9-20 km southeast of the fault trace, earthquakes are much more prevalent and shallower than 7 km. Hypocenter lineations here are subparallel to faults mapped near the Main Divide of the Southern Alps, confirming that those faults are active. The region of enhanced seismicity is associated with the highest topography and a high-velocity tongue doming at 3-5 km depth. The low-seismicity zone adjacent to the Alpine Fault trace is associated with Vp and Vs values at midcrustal depths about 8 and 6% lower than further southeast. We interpret lateral variations in seismicity rate to reflect patterns of horizontal strain rate superimposed on heterogeneous crustal structure, and the variations in seismicity cutoff depth to be controlled by temperature and permeability structure variations.

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Section: Discussionmentioning

confidence: 99%

Structural heterogeneity of the midcrust adjacent to the central Alpine Fault, New Zealand: Inferences from seismic tomography and seismicity between Harihari and Ross

Bourguignon

Bannister

Henderson

et al. 2015

Geochem Geophys Geosyst

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“…A possible physical explanation for this observation is nonuniform distribution of frictional resistance (fault strength) and stress concentrations (e.g., Rivera and Kanamori, 2002). The influence of varying fault strength on sourcescaling properties has been discussed often (e.g., Das and Scholz, 1983;Strehlau, 1986;Bodin and Brune, 1996;Mai and Beroza, 2000;Shaw and Scholz, 2001;Miller, 2002;Wesnousky, 2006;Lozos et al, 2015). The fault strength tends to increase with depth, which in turn would restrict down-dip seismic slip (Das and Scholz, 1983;Strehlau, 1986).…”

Section: Variability Of Source-scaling Propertiesmentioning

confidence: 99%

“…The influence of varying fault strength on sourcescaling properties has been discussed often (e.g., Das and Scholz, 1983;Strehlau, 1986;Bodin and Brune, 1996;Mai and Beroza, 2000;Shaw and Scholz, 2001;Miller, 2002;Wesnousky, 2006;Lozos et al, 2015). The fault strength tends to increase with depth, which in turn would restrict down-dip seismic slip (Das and Scholz, 1983;Strehlau, 1986). On the other hand, longer ruptures are associated with along-strike zones of low fault strength or high shear stress (Wesnousky, 2006;Lozos et al, 2015).…”

Section: Variability Of Source-scaling Propertiesmentioning

confidence: 99%

New Empirical Earthquake Source‐Scaling Laws

Thingbaijam

Martin

Goda

2017

Bulletin of the Seismological Society of America

239

175

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We develop new empirical scaling laws for rupture width W, rupture length L, rupture area A, and average slip D, based on a large database of rupture models. The database incorporates recent earthquake source models in a wide magnitude range (M w 5.4-9.2) and events of various faulting styles. We apply general orthogonal regression, instead of ordinary least-squares regression, to account for measurement errors of all variables and to obtain mutually self-consistent relationships. We observe that L grows more rapidly with M w compared to W. The fault-aspect ratio (L=W) tends to increase with fault dip, which generally increases from reversefaulting, to normal-faulting, to strike-slip events. At the same time, subduction-interface earthquakes have significantly higher W (hence a larger rupture area A) compared to other faulting regimes. For strike-slip events, the growth of W with M w is strongly inhibited, whereas the scaling of L agrees with the L-model behavior (D correlated with L). However, at a regional scale for which seismogenic depth is essentially fixed, the scaling behavior corresponds to the W model (D not correlated with L). Selfsimilar scaling behavior with M w − log 10 A is observed to be consistent for all the cases, except for normal-faulting events. Interestingly, the ratio D=W (a proxy for average stress drop) tends to increase with M w , except for shallow crustal reversefaulting events, suggesting the possibility of scale-dependent stress drop. The observed variations in source-scaling properties for different faulting regimes can be interpreted in terms of geological and seismological factors. We find substantial differences between our new scaling relationships and those of previous studies. Therefore, our study provides critical updates on source-scaling relations needed in seismic-tsunami-hazard analysis and engineering applications. Electronic Supplement: Figures depicting regression analysis, normality probability plots, and comparisons between different source-scaling relationships; and tables listing rupture models and different earthquake source-scaling relationships.

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“…the 2018 Zakynthos earthquake produced a deep rupture whose downdip extent approached 38 km, which implies the presence of a low coefficient of dynamic friction (Strehlau, 1986). The fact that the rupture penetrated quite deep is also implied by the USGS W-phase moment tensor solution and the global CMT solution.…”

Section: Geophysical Research Lettersmentioning

confidence: 91%

Intraslab Deformation and Rupture of the Entire Subducting Crust During the 25 October 2018 Mw 6.8 Zakynthos Earthquake

Chousianitis

Konca

2019

Geophysical Research Letters

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We constrained the rupture process of the 25 October 2018 M w 6.8 Zakynthos earthquake by jointly inverting near-fault strong motion records, static, and high-rate GPS displacements along with teleseismic waveforms. The inverted slip distribution is characterized by two asperities with peak slip amplitude of 1.4 m, which is located at 17 km depth. The rupture essentially propagated unilaterally in the downdip direction after the initiation and to the north-northeast toward Zakynthos island. The earthquake produced a deep rupture whose downdip extent approached 38 km, indicating that this event broke the entire underthrust Ionian oceanic crust beneath the megathrust and penetrated into the top few kilometers of the solid uppermost mantle. The extent of the rupture implied the presence of a low coefficient of dynamic friction. The mainshock triggered a counterclockwise rotation of the stress field with respect to the long-term regional stress. Aftershocks occurred at shallower depths than the coseismic slip zone.Plain Language Summary On 25 October 2018 a major earthquake occurred 45 km SSW of Zakynthos Island at Western Greece. The region where the earthquake struck is one of the most active seismic zones in the country. It is where the active Hellenic subduction, that is, the interface along which the Nubia plate subducts under the Aegean plate, reaches the Cephalonia Transform Fault. We jointly used seismic and geodetic data sets to study the 2018 Zakynthos earthquake and revealed that it was not a typical subduction or a transform fault event; it was something different. By constraining the rupture process of the earthquake, we showed that this event did not slip the megathrust surface of the subduction zone but instead fractured the entire underthrust Ionian oceanic crust as it descends beneath the Aegean plate suggesting intraslab deformation and probably tearing of the subducting slab. Furthermore, the main shock induced a counterclockwise rotation of the stress field with respect to the long-term regional stress.

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A Discussion of the Depth Extent of Rupture in Large Continental Earthquakes

Cited by 50 publications

References 71 publications

Structural heterogeneity of the midcrust adjacent to the central Alpine Fault, New Zealand: Inferences from seismic tomography and seismicity between Harihari and Ross

Structural heterogeneity of the midcrust adjacent to the central Alpine Fault, New Zealand: Inferences from seismic tomography and seismicity between Harihari and Ross

New Empirical Earthquake Source‐Scaling Laws

Intraslab Deformation and Rupture of the Entire Subducting Crust During the 25 October 2018 Mw 6.8 Zakynthos Earthquake

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