On the Depth Extent of Coseismic Rupture

Beeler, N. M.; Hirth, Greg; Tullis, Terry E.; Webb, Charles Harper

doi:10.1785/0120160295

Cited by 12 publications

(9 citation statements)

References 71 publications

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“…Many factors including temperature, strain rate, pore fluid pressure, lithology, water content, fault geometry, and stress regime (Scholz, 1998; Sibson, 1984; Zoback & Townend, 2001) affect the depth of the BDT zone, which roughly corresponds to the maximum depths of low‐ and moderate‐magnitude seismicity (Chen & Molnar, 1983; Scholz, 1988; Sibson, 1982, 1984) and the depth to which rupture extends in large earthquakes (Jackson, 2002; Magistrale & Zhou, 1996; Sibson, 1982, 1984). Recent studies however have suggested that large earthquakes sometimes or always also rupture the deeper creeping section of the fault zone (Beeler et al., 2018; Jiang & Lapusta, 2016; Shaw & Wesnousky, 2008).…”

Section: Introductionmentioning

confidence: 99%

Crustal Thermal Structure and Exhumation Rates in the Southern Alps Near the Central Alpine Fault, New Zealand

Michailos

Sutherland

Townend

et al. 2020

Geochem Geophys Geosyst

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We investigate orogenic uplift rates and the thermal structure of the crust in the hanging wall of the Alpine Fault, New Zealand, using the hypocenters of 7,719 earthquakes that occurred in the central Southern Alps between late 2008 and early 2017, and previously published thermochronological data. We assume that the base of the seismogenic zone corresponds to a brittle‐ductile transition at some fixed temperature, which we estimate by fitting the combined thermochronological data and distribution of seismicity using a multi‐1‐D approach. We find that exhumation rates vary from 1 to 8 mm/yr, with maximum values observed in the area of highest topography near Aoraki/Mount Cook, a finding consistent with previous geologic and geodetic analyses. We estimate the temperature of the brittle‐ductile transition beneath the Southern Alps to be 410–430°C, which is higher than expected for Alpine Fault rocks whose bulk lithology is likely dominated by quartz. The high estimated temperatures at the base of the seismogenic zone likely reflect the unmodeled effects of high fluid pressures or strain rates.

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Section: Introductionmentioning

confidence: 99%

Crustal Thermal Structure and Exhumation Rates in the Southern Alps Near the Central Alpine Fault, New Zealand

Michailos

Sutherland

Townend

et al. 2020

Geochem Geophys Geosyst

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“…Indeed, aftershocks are sometimes recorded at depths slightly greater than those of the mainshock and of the background seismicity during 'quiescence' periods. Considering that the seismotectonic setting discussed by Rolandone et al [2004] and Beeler et al [2018] certainly smaller (and hence the coseismic slip is comparably shorter), iii) slip-and strain-rate are both more diffuse within the investigated crustal volumes than the only 100 m-thick shear zone assumed by the authors, a reasonable value of a sufficiently thick interposed ductile layer is 500 m.…”

Section: Methodological Approachmentioning

confidence: 82%

“…At this regard, seismological evidences [e.g. Rolandone et al, 2004] and mechanical-rheological modelling [Beeler et al, 2018] have proved that the embrittlement caused by the temporary increase of the strain rate after a major seismic event may result in a sudden and transient deepening of the BDT, with respect to the interseismic period depth, in the range of 1-3 km. Indeed, aftershocks are sometimes recorded at depths slightly greater than those of the mainshock and of the background seismicity during 'quiescence' periods.…”

Section: Methodological Approachmentioning

confidence: 99%

Sensitivity analysis for crustal rheological profiles: examples from the Aegean Region

Maggini

Caputo

2020

Annals of Geophysics

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We tested the validity of rheological profiles and their sensitivity to variations in the input parameters, with particular emphasis on the resulting BDT (brittle-ductile transition) depth and corresponding strength and temperature. For this purpose, we selected two test-sites from the Aegean Region, one in an extensional tectonic setting and the other in a strike-slip regime, and carefully realized the corresponding "reference" rheological profiles based on literature data and specific geological constraints. The reference envelopes have been then compared with a set of different profiles realized by varying the input parameters of the constitutive equations of the brittle and ductile behaviours within reasonable ranges. Firstly, tests were performed by changing the value of only one input parameter per time, with the aim of quantifying and comparing its influence on the BDT properties. The parameters exerting the greatest control are the activation energy, the power-law exponent and the surface heat flow (through its influence on the geothermal gradient), for the creep behaviour. As regards the brittle behaviour parameters, the friction coefficient and the pore fluid pressure could play a significant role especially in determining the maximum strength. In a second phase, we simultaneously varied all the input parameters in order to consider the possible synergistic effects on the resulting rheological profiles and to verify the likelihood and consistency of the reference models. For the statistical approach, one hundred thousand random combinations of the analysed parameters have been generated. The particular care spent on selecting the range of values of each parameter is reflected in the results of the statistical analyses, which show a good agreement with the reference profiles and allow estimating the overall uncertainties. Finally, the obtained strength envelopes have been compared with the accurately relocated depth distribution of recent seismic sequences that affected the two test areas. In both cases, the depth corresponding to the 95% of the total released energy nicely fits the BDT depth obtained from the rheological modelling, therefore confirming that this parameter could represent a reasonable and reliable approximation of the seismogenic layer thickness.

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“…In order to define this transition, in the event that a deeper second brittle layer occurs, it is assumed that an interposed ductile layer with a thickness of at least 0.5 km is sufficient to mechanically decouple the two brittle layers in terms of seismogenic behaviour and hence seismic potential. In other words, a 0.5-km-thick interposed ductile layer could be considered an adequate 'obstacle' for hindering the propagation of a coseismic rupture from one brittle layer to another one along a hypothetical fault (Rolandone et al, 2004;Beeler et al, 2018), thus making the two hypothetically aligned segments independent of each other in seismological terms.…”

Section: Thermo-rheological Modelling For Oceanic and Continental Litmentioning

confidence: 99%

Rheological behaviour in continental and oceanic subduction: inferences for the seismotectonics of the Aegean Region

2020

Turkish J Earth Sci

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We reconstructed several rheological transects across the Aegean Region, comparing the behaviour in collisional versus subducting settings. We interpolated closely spaced 1D strength envelopes, realized through a dedicated MATLAB script, for determining the shallow lithospheric distribution of brittle and ductile layers. We mainly used literature data and geodynamic considerations to fix the parameters for the rheological modelling and took particular care in reproducing reliable thermal models. The results of the mechanical-rheological model highlighted the following features and differences between the northern continental collision and the southern oceanic subduction settings: i) a slightly shallower brittle-ductile transition (BDT) in the western sectors of the northern transects (~30-33 km) with respect to the southern ones (~40 km); ii) on the contrary, in the central-eastern sectors of the investigated area, corresponding to an extensional tectonic regime, the northern transects have a relatively deeper BDT (about 20-25 km) compared with the southern ones (about 15 km); iii) the occurrence of a thick, deeper brittle layer below the shallowest BDT, in the centraleastern sectors of the northern transects. We suggest that such regional differences are mainly related and attributable to the surface heat flow distribution (which directly affects the geothermal gradient) and to the tectonic and geodynamic context. The results of the rheological modelling in terms of depth extent of the brittle layer(s) have been compared with the depth distribution of available relocated seismicity, showing good agreement with the rheological layering proposed here. Finally, the depth of the shallowest BDT along the transects has been adopted as a constraint for the seismogenic layer thickness. Such information has been used to improve the seismotectonic characterization of selected crustal seismogenic sources crossing the transects, by estimating their maximum potential magnitudes on the basis of their geometrical features and consistency with the rheological layering.

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On the Depth Extent of Coseismic Rupture

Cited by 12 publications

References 71 publications

Crustal Thermal Structure and Exhumation Rates in the Southern Alps Near the Central Alpine Fault, New Zealand

Crustal Thermal Structure and Exhumation Rates in the Southern Alps Near the Central Alpine Fault, New Zealand

Sensitivity analysis for crustal rheological profiles: examples from the Aegean Region

Rheological behaviour in continental and oceanic subduction: inferences for the seismotectonics of the Aegean Region

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