Episodic stress and fluid pressure cycling in subducting oceanic crust during slow slip

Warren‐Smith, Emily; Fry, Bill; Wallace, Laura; Chon, E.; Henrys, S. A.; Sheehan, A. F.; Mochizuki, Kimihiro; Schwartz, S. Y.; Webb, Spahr C.; Lebedev, Sergei

doi:10.1038/s41561-019-0367-x

Cited by 134 publications

(186 citation statements)

References 56 publications

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“…In the north they find that SH max is oriented NE‐SW, parallel to the Hikurangi trench in a strike‐slip stress regime. The NE‐SW orientation of SH max in this area is also observed by Warren‐Smith et al (), though they observe a normal faulting stress regime in the subducting plate. In contrast, in the southern forearc Townend et al () find that SH max is oriented ENE‐WSW, sub‐parallel to the Hikurangi plate motion in a normal stress regime.…”

Section: Discussionsupporting

confidence: 84%

Mapping Stress and Structure From Subducting Slab to Magmatic Rift: Crustal Seismic Anisotropy of the North Island, New Zealand

Illsley‐Kemp

Savage

Wilson

et al. 2019

Geochem Geophys Geosyst

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We use crustal seismic anisotropy measurements in the North Island, New Zealand, to examine structures and stress within the Taupō Volcanic Zone, the Taranaki Volcanic Lineament, the subducting Hikurangi slab, and the Hikurangi forearc. Results in the Taranaki region are consistent with NW‐SE oriented extension yet suggest that the Taranaki volcanic lineament may be controlled by a deep‐rooted, inherited crustal structure. In the central Taupō Volcanic Zone anisotropy fast orientations are predominantly controlled by continental rifting. However at Taupō and Okataina volcanoes, fast orientations are highly variable and radial to the calderas suggesting the influence of magma reservoirs in the seismogenic crust (≤15 km depth). The subducting Hikurangi slab has a predominant trench‐parallel fast orientation, reflecting the pervasive presence of plate‐bending faults, yet changing orientations at depths ≥120 km beneath the central North Island may be relics from previous subduction configurations. Finally, results from the southern Hikurangi forearc show that the orientation of stresses there is consistent with those in the underlying subducting slab. In contrast, the northern Hikurangi forearc is pervasively fractured and is undergoing E‐W compression, oblique to the stress field in the subducting slab. The north‐south variation in fore‐arc stress is likely related to differing subduction‐interface coupling. Across the varying tectonic regimes of the North Island our study highlights that large‐scale tectonic forces tend to dictate the orientation of stress and structures within the crust, although more localized features (plate coupling, magma reservoirs, and inherited crustal structures) can strongly influence surface magmatism and the crustal stress field.

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Section: Discussionsupporting

confidence: 84%

Mapping Stress and Structure From Subducting Slab to Magmatic Rift: Crustal Seismic Anisotropy of the North Island, New Zealand

Illsley‐Kemp

Savage

Wilson

et al. 2019

Geochem Geophys Geosyst

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“…We applied our model to real pressure data collected by the HOBITSS project in New Zealand between June 2014 and March 2015, during which at least two SSEs have been identified (Muramoto et al, 2019; Wallace et al, 2016; Warren‐Smith et al, 2019). Before application, we built a synthetic data set with mixed SNRs and ramp durations to train our model.…”

Section: Resultsmentioning

confidence: 99%

Detecting Slow Slip Events From Seafloor Pressure Data Using Machine Learning

Wei

Watts

et al. 2020

Geophysical Research Letters

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Detecting slow slip events (SSEs) at offshore subduction zones is important to understand the slip behavior on offshore subduction megathrusts, where tsunamis can be generated. The most widely used method to detect SSEs is to measure the vertical seafloor deformation caused by SSEs using seafloor pressure data. However, due to the small signal‐to‐noise ratio and instrumental drift, such detection is very difficult. In this study, we trained a machine learning model using synthetic data to detect SSEs and applied it to real pressure data in New Zealand between 2014 and 2015. Our method detected five events, two of which are confirmed by the onshore GPS records. Besides, our model performs better than the traditional matched filter method. We conclude that machine learning could be used to detect SSEs in real seafloor pressure data. The method can be applied to other regions, especially where near trench GPS is not available.

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“…Thus, we prefer that the high‐ν anomalies in the lowermost portion of the crust and the cold nose of the mantle wedge in the Upper and Lower Cook Inlet are probably related to ascending fluids released from slab dehydration. High pore pressure induced by the fluids may lower the effective normal stress, promote the failure of the plate interface, and finally contribute to repeating occurrences of the SSEs as revealed by the observations and numerical modeling (Audet & Bürgmann, ; Y. Liu & Rice, ; Wannamaker et al, ; Warren‐Smith et al, ). Our results indicate that the existence of the localized fluids on the megathrust interface is probably one of the key factors resulting in the along‐strike SSE segmentation in south‐central Alaska, in addition to a lateral transition from the buoyant, flat subduction to the normal subduction (H. Li et al, ).…”

Section: Discussionmentioning

confidence: 99%

Structural Heterogeneity in Source Zones of the 2018 Anchorage Intraslab Earthquake and the 1964 Alaska Megathrust Earthquake

Gou

Zhao

Huang

et al. 2020

Geochem Geophys Geosyst

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Structural heterogeneities in subduction zones can affect slip behaviors of the megathrust faults and the generation of intraslab earthquakes. In this work we study the 3‐D seismic structures (Vp, Vs, and Poisson's ratio) in and around the source zones of the 2018 Anchorage intraslab earthquake (Mw 7.1) and the 1964 Alaska megathrust earthquake (Mw 9.2). The Anchorage earthquake occurred in an anomalous zone within the subducting Yakutat/Pacific plate with a higher Poisson's ratio than the normal slab. Above the source zone, the overriding North American plate shows a low Vs and a high Poisson's ratio. These features indicate that strong dehydration occurs in the source zone and released fluids ascend into the overlying crust. Two areas with long‐term slow slip events in the Upper and Lower Cook Inlet predominantly exhibit a high Poisson's ratio in the lowermost portion of the crust and the cold nose of the mantle wedge, whereas a low Poisson's ratio zone is revealed between them, suggesting that their segmentation is possibly related to localized slab‐releasing fluids. In the Prince William Sound, the rupture of the 1964 Great Alaska earthquake initiated beneath a high‐V and high Poisson's ratio zone of the overlying crust and the large slips occurred beneath a low‐Vs and high Poisson's ratio zone, suggesting that lateral heterogeneities of the overriding plate may have played an important role in the nucleation and rupture processes of the Great Alaska earthquake.

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Episodic stress and fluid pressure cycling in subducting oceanic crust during slow slip

Cited by 134 publications

References 56 publications

Mapping Stress and Structure From Subducting Slab to Magmatic Rift: Crustal Seismic Anisotropy of the North Island, New Zealand

Mapping Stress and Structure From Subducting Slab to Magmatic Rift: Crustal Seismic Anisotropy of the North Island, New Zealand

Detecting Slow Slip Events From Seafloor Pressure Data Using Machine Learning

Structural Heterogeneity in Source Zones of the 2018 Anchorage Intraslab Earthquake and the 1964 Alaska Megathrust Earthquake

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