Temporal Stress Changes Caused by Earthquakes: A Review

Hardebeck, Jeanne L.; Okada, Tomomi

doi:10.1002/2017jb014617

Cited by 113 publications

(102 citation statements)

References 83 publications

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“…At such depths, brittle seismic failure of the dry anorthosite host rock requires differential stresses in excess of hundreds of megapascals (Figure a). Hence, even when the stress drop is nearly complete (i.e., for Δ τ / τ in the range of 0.6–0.9, where Δ τ is the earthquake stress drop and τ is the maximum shear stress on the seismogenic fault plane in the pre‐earthquake stress field; Hardebeck & Okada, ), residual differential stresses during the postseismic period could be expected to be on the order of 100 MPa after a ~1‐GPa coseismic stress drop. While long‐term, steady‐state viscous creep localized on the shear zones (including along the mylonitized pseudotachylytes) in Nusfjord may generally have taken place at more typical geological strain rates of 10 −15 –10 −13 s −1 (Fagereng & Biggs, ) under relatively low differential stresses during the interseismic period (i.e., blue curves in Figure a), transient higher differential stresses and strain rates, such as 10 −9 s −1 derived in this study, can also be supported by localized viscous creep in the same material (orange curve in Figure a).…”

Section: Discussionmentioning

confidence: 99%

Transient High Strain Rate During Localized Viscous Creep in the Dry Lower Continental Crust (Lofoten, Norway)

Campbell

Menegon

2019

JGR Solid Earth

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Understanding the ability of the lower crust to support transient changes in stresses and strain rates during the earthquake cycle requires a detailed investigation of the deformation mechanisms and rheology of deep crustal fault rocks. Here, we show that lower crustal pseudotachylyte-bearing shear zones are able to accommodate short-term episodes of high strain rate and high stress deformation by accelerated viscous creep, followed by a reduction in stresses to some ambient deformation condition. Quartz microstructure within pseudotachylyte-bearing shear zones in otherwise undeformed granulites from Lofoten, Norway, indicates that dynamic recrystallization occurred during viscous creep under rapid strain rates and high stresses of~10 −9 s −1 and~100 MPa, respectively. Lower stress microstructures (i.e., foam textures) are also recorded in the shear zones, indicating spatial and temporal variations of stress and strain rate during deformation cycles. Both the high and lower stress quartz recrystallization took place under granulite facies conditions of 650°C-750°C and 0.7-0.8 GPa and represented a record of highly localized viscous creep within the lower crust. This implies that lower crustal pseudotachylytes are potentially able to form extremely localized weak zones within strong lower crust, enabling a deep mechanical response to perturbations in stress and strain rate such as those experienced during the seismic cycle, for example, seismogenic loading followed by subsequent postseismic relaxation.Plain Language Summary Detailed investigation of the strength and deformation style of fault rocks sourced from the Earth's lower crust is important to understand how the lower crust reacts to shortterm variations in stress and strain rate, which can occur, for example, between earthquakes. Here, we show that solidified pseudotachylytes (initially melts produced due to frictional heating along the fault plane during an earthquake) occurring at depths of 25-30 km in the lower crust can accommodate deformation at particularly high strain rates and high stresses via solid-state creep. We look at pseudotachylytes formed in lower crustal shear zones that are now exhumed in Lofoten, Norway. Deformation microstructures in quartz within these pseudotachylytes have recorded rapid strain rates and high stresses. These microstructures are occasionally transformed into lower stress versions, indicating that during the deformation the stress and strain rate varied through both time and space. Both stages, however, record the same deformation temperatures and pressures, indicating that these are snapshots of ongoing deformation within the lower crust. We conclude that, when the lower crust is strong, pseudotachylytes will form important weak zones that accommodate deformation even during rapid variations in the deformation conditions, for example, as occurs during the postseismic period immediately after an earthquake.

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Section: Discussionmentioning

confidence: 99%

Transient High Strain Rate During Localized Viscous Creep in the Dry Lower Continental Crust (Lofoten, Norway)

Campbell

Menegon

2019

JGR Solid Earth

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“…A stress drop of E1 on the order of differential stress (i.e., σ 1 − σ 3 ) in the crust can produce a localized, transient rotation of the stress field (Hardebeck & Okada, and references therein), which can preferentially orient the local stress field temporarily to promote rupture on faults suboptimally oriented. Using Yin and Rogers' () equations and principal stress magnitudes estimated by Nelson et al () for the Gippsland Basin, we estimated that E1 rotated the local stress field by about 10° toward the normal to Fault 1.…”

Section: Discussionmentioning

confidence: 99%

Interacting Intraplate Fault Systems in Australia: The 2012 Thorpdale, Victoria, Seismic Sequences

Attanayake

Sandiford

Schleicher³

et al. 2019

JGR Solid Earth

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Using a new seismic waveform data set, we locate 234 earthquakes and estimate source parameters (focal mechanisms, magnitude, and stress drop) of the two largest earthquakes (E1 and E2) in the 2012 seismic sequence in Thorpdale, Victoria. The focal mechanisms suggest thrust faulting, consistent with previous observations in southeast Australia. The estimated magnitudes are M w 4.9 ± 0.14 (E1) and 4.3 ± 0.1 (E2). The estimates of stress drop 57 ± 7.4 MPa (E1) and 28 ± 2.4 MPa (E2) reflect strength of faults in an intraplate environment. By analyzing spatiotemporal distribution of aftershocks, we show that E1 and E2 reflect two separate seismic sequences about a month apart. E1 and E2 ruptured two adjacent faults with orientations 218°/78°/78°(Fault 1) and 134°/27°/171°(Fault 2), respectively, where angles indicate strike/dip/slip rake. To test causal mechanism of fault interaction, we performed Coulomb stress modeling, which shows very weak unloading of E2 by E1. Thus, we infer that fault interaction might instead reflect remotely triggered fluid diffusion. Also, a local rotation of the stress field proceeding E1 might have favorably reoriented Fault 2 for failure. Finally, we identify an apparent correlation between high heat flow and seismicity in southeastern Australia, suggesting a combination of mechanisms including transient stress perturbations and lithospheric thermal weakening associated with high heat flow as the principal factors localizing intraplate seismicity.Plain Language Summary The 2012 earthquake sequence in Thorpdale is the most recent and significant seismic activity in southeast Australia, during which two moderate-sized earthquakes were felt in the region with the second earthquake thought to be an aftershock of the first. Using a newly assembled data set, we estimate source parameters of these earthquakes and locate 232 smaller earthquakes associated with this seismic sequence. In this study, we show that faults ruptured with thrust motion, the moment magnitude of the two largest earthquakes are 4.9 and 4.3, and the stress release per fault length (57 and 28 MPa) is larger than the global average. By locating aftershocks, we also show that the two largest earthquakes ruptured two separate faults rather than one. The absence of any plausible Coulomb stress loading suggests that these different faults interacted with each other through other mechanisms such as a fluid diffusion. Key Points:• The two largest earthquakes (M w 4.9 and 4.3) in the seismic sequence indicate thrust faulting in southeast Australia • Higher than average stress drop (57 and 28 MPa) suggests the rupture of strong faults with longer recurrence intervals • Adjacent fault planes ruptured, implying fault interaction through interplay between stress conditions and fluid diffusion Supporting Information:• Supporting Information S1

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“…Except for the faulting style, the stress fields within the aftershock area, estimated from the two datasets (before and after the mainshock), have common characteristics. The difference in the faulting style is likely caused by coseismic stress perturbation (Hardebeck and Okada 2018). However, as shown later (Section 5.2), we infer that this temporal change in the stress field is an artifact caused by incomplete data sampling before the mainshock.…”

Section: Stress Field In and Around The Awaji Island Earthquakementioning

confidence: 52%

Driving Stress and Seismotectonic Implications of the 2013 Mw5.8 Awaji Island Earthquake, Southwestern Japan, Based on Earthquake Focal Mechanisms Before and After the Mainshock

Imanishi

Ohtani

Uchide

2020

Preprint

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Abstract A driving stress of the M w 5.8 reverse-faulting Awaji Island earthquake (2013), southwest Japan, was investigated using focal mechanism solutions of earthquakes before and after the mainshock. The seismic records from regional high-sensitivity seismic stations were used. Further, the stress tensor inversion method was applied to infer the stress fields in the source region. The results of the stress tensor inversion and the slip tendency analysis revealed that the stress field within the source region deviates from the surrounding area, in which the stress field locally contains a reverse-faulting component with ENE-WSW compression. This local fluctuation in the stress field is key to producing reverse-faulting earthquakes. The existing knowledge on regional-scale stress (tens to hundreds of km) cannot predict the occurrence of the Awaji Island earthquake, emphasizing the importance of estimating local-scale (< tens of km) stress information. It is possible that the local-scale stress heterogeneity has been formed by local tectonic movement, i.e., the formation of flexures in combination with recurring deep aseismic slips. The coseismic Coulomb stress change, induced by the disastrous 1995 M w 6.9 Kobe earthquake, increased along the fault plane of the Awaji Island earthquake; however, the postseismic stress change was negative. We concluded that the gradual stress build-up, due to the interseismic plate locking along the Nankai trough, overcame the postseismic stress reduction in a few years, pushing the Awaji Island earthquake fault over its failure threshold in 2013. The observation that the earthquake occurred in response to the interseismic plate locking has an important implication in terms of seismotectonics in southwest Japan, facilitating further research on the causal relationship between the inland earthquake activity and the Nankai trough earthquake. Furthermore, this study highlighted that the dataset before the mainshock may not have sufficient information to reflect the stress field in the source region due to the lack of earthquakes in that region. This is because the earthquake fault is generally locked prior to the mainshock. Further research is needed for estimating the stress field in the vicinity of an earthquake fault via seismicity before the mainshock alone.

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Temporal Stress Changes Caused by Earthquakes: A Review

Cited by 113 publications

References 83 publications

Transient High Strain Rate During Localized Viscous Creep in the Dry Lower Continental Crust (Lofoten, Norway)

Transient High Strain Rate During Localized Viscous Creep in the Dry Lower Continental Crust (Lofoten, Norway)

Interacting Intraplate Fault Systems in Australia: The 2012 Thorpdale, Victoria, Seismic Sequences

Driving Stress and Seismotectonic Implications of the 2013 Mw5.8 Awaji Island Earthquake, Southwestern Japan, Based on Earthquake Focal Mechanisms Before and After the Mainshock

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