Toward Waveform‐Based Characterization of Slab &amp; Mantle Wedge (SAM) Earthquakes

Halpaap, Felix; Rondenay, S.; Liu, Qinya; Millet, F.; Ottemöller, Lars

doi:10.1029/2020jb021573

Cited by 2 publications

(18 citation statements)

References 108 publications

(178 reference statements)

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“…This is also where hydrous minerals should be concentrated, within the subducting slab (Kirby et al, 1996). Additionally, intermediate-depth earthquakes also tend to be concentrated along dehydration reaction boundaries which exist in the slab crust and slab mantle, which give rise to DSZs (Yamasaki and Seno, 2003;Halpaap et al, 2021). The earthquakes which will be located with high accuracy in this thesis will give us reliable insight into where hydrous minerals are constrained within the subducting slab and therefore where fluids are likely to be released from the slab.…”

Section: Mechanisms For Intermediate-depth Seismicity and Dszsmentioning

confidence: 90%

“…Often, intermediate-depth earthquakes occur within the top few kilometres of the subducting slab, however, double seismic zones (DSZs) are also common with seismicity being prominent to as deep as ∼40 km in the slab (Hasegawa et al, 1978a;Hacker et al, 2003;Yamasaki and Seno, 2003;Nakajima et al, 2013). Studies have shown that intermediate-depth earthquakes may occur in the slab mantle, in the subducting crust, on the plate interface (down to ∼90 km), or in the mantle wedge (Hacker et al, 2003;Yamasaki and Seno, 2003;Boneh et al, 2019;Halpaap et al, 2021). In cold subduction zones earthquakes are more likely to occur in the slab crust and mantle, while in warm subduction zones, earthquakes often only occur in the slab mantle (Abers et al, 2013).…”

Section: Occurrence Of Intermediate-depth Seismicitymentioning

confidence: 99%

“…In cold subduction zones earthquakes are more likely to occur in the slab crust and mantle, while in warm subduction zones, earthquakes often only occur in the slab mantle (Abers et al, 2013). It is possible for earthquakes to occur in the mantle wedge, but this is rare (Halpaap et al, 2021). Some studies have been able to distinguish mantle wedge earthquakes from those in the slab, although this is a select few (Davey and Ristau, 2011;Malusà et al, 2017;Halpaap et al, 2019).…”

Section: Occurrence Of Intermediate-depth Seismicitymentioning

confidence: 99%

“…In DSZs the seismicity occurs in two distinct planes which are separated vertically by an aseismic layer in which anhydrous minerals persist in the thermally cold core of the slab (Hacker et al, 2003). The upper plane usually exists in the upper portion of the oceanic crust and uppermost mantle and is separated by 20-40 km from the lower plane (Wei et al, 2017;Chu et al, 2019;Ciaccio et al, 2021;Halpaap et al, 2021). The lower plane lies parallel, much deeper in the slab, in the subducting oceanic mantle (Manning, 2004;Wei et al, 2017).…”

Section: Mechanisms For Intermediate-depth Seismicity and Dszsmentioning

confidence: 99%

“…Earthquake locations can be further constrained by reflected and converted phases which are produced at various discontinuities below Earth's surface (Figure 1.5) (Halpaap et al, 2021). Discontinuities in Earth's subsurface may represent phase mic ray paths (Halpaap et al, 2019).…”

Section: Seismic Phase Conversion and Reflectionmentioning

confidence: 99%

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Exploring the Nature and Influence of Intermediate-Depth Seismicity Beneath the Taupō Volcanic Zone

Mark

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The central Taupō Volcanic Zone (TVZ) hosts the most productive rhyolitic volcanic system in the world. A link has been proposed between the composition of deep subduction fluids and the extreme productivity of the caldera volcanoes in the central TVZ (Taupō and Ōkataina), largely based on geochemical studies. It is hypothesised that fluids freed from dehydration reactions in the subducting slab facilitate intermediate-depth earthquakes through dehydration-related embrittlement. These fluids can migrate into the mantle wedge and contribute to partial melting of the primitive magma source, which influences the flux of magmas to the central TVZ calderas. In this thesis we aim to investigate the potential link between these earthquakes and the subduction fluid signature that is present in the central TVZ caldera volcanoes. Well-constrained earthquake locations and their faulting parameters can help us better understand this relationship. The new earthquake catalogue produced in this thesis contains 397 earthquakes between depths of 50–305 km. These were located with 40,266 manual P- and S-picks, a 3D velocity model, and relocated using relative relocation techniques. These locations are further refined by observations of converted and reflected seismic phases, unique to earthquakes nucleating in various regions of the subducting slab. We observe a double seismic zone (DSZ) beneath the central TVZ. This occurs in one section of the slab, at depths of 145–190 km and the seismic planes are separated by an aseismic plane <8 km wide. The stress state of the subducting slab, as determined by 47 focal mechanisms, has an upper seismic plane in down-dip extension and a lower seismic plane in down-dip compression. We also identify earthquakes occurring in the mantle wedge whose computed focal mechanisms indicate that they typically occur on near vertical faults. The pattern of intermediate-depth seismicity we observe is consistent with earthquakes being facilitated by dehydration reactions in the oceanic slab crust and mantle. The abundant fluids released from these reactions have distinct geochemical signatures, that have been previously identified in the eruptive products of the caldera volcanoes in the central TVZ. We therefore provide evidence of a link between intermediate-depth seismicity and magmatism in the central TVZ. Additionally, the uniqueness of the Hikurangi slab, which has an unusually high fracture permeability, its oblique subduction beneath the North Island and its thermo-mechanic structure, is likely a significant contributor to the anomalous rhyolitic volcanism observed in the central TVZ.

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Section: Mechanisms For Intermediate-depth Seismicity and Dszsmentioning

confidence: 90%

Section: Occurrence Of Intermediate-depth Seismicitymentioning

confidence: 99%

Section: Occurrence Of Intermediate-depth Seismicitymentioning

confidence: 99%

Section: Mechanisms For Intermediate-depth Seismicity and Dszsmentioning

confidence: 99%

Section: Seismic Phase Conversion and Reflectionmentioning

confidence: 99%

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Exploring the Nature and Influence of Intermediate-Depth Seismicity Beneath the Taupō Volcanic Zone

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Evidence From Intermediate‐Depth Earthquakes of Slab‐Derived Fluids Beneath the Taupō Volcanic Zone

Mark,

Illsley‐Kemp,

Townend

et al. 2024

JGR Solid Earth

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Ahi Tupua, the central section of the Taupō Volcanic Zone in the central North Island of New Zealand, encompasses Taupō and Ōkataina calderas and has been the most frequently active and productive silicic magma system worldwide during the Quaternary. The entire Taupō Volcanic Zone is underlain by the Hikurangi Subduction Zone where a Large Igneous Province, the Hikurangi Plateau, is being subducted, but Ahi Tupua exhibits much higher rates of magma output than either the northern or the southern sections. Trace element signatures of Ahi Tupua eruptive products suggest that both decompression melting and flux melting play a role in this rifted arc setting, with fluid flux signatures being more prevalent in regions of active caldera volcanism. Intermediate‐depth (50–300 km) earthquakes provide a means of studying faulting and fluid flow processes within and around the subducting slab beneath Ahi Tupua. Using data from the national seismic network and a 13‐station temporary network (“ECLIPSE”), we repick and relocate 397 intermediate‐depth earthquakes of magnitudes M2.5+ that occurred in a 29‐month interval, and compute focal mechanisms for a subset of 47 earthquakes. We observe some seismicity that may be within the mantle wedge but most of the relocated earthquakes occur within the crust and uppermost mantle of the subducted slab and exhibit a weak transition from predominantly normal‐faulting in the slab crust to predominantly reverse‐faulting in the slab mantle. No double seismic zone is observed beneath Ahi Tupua. These observations are consistent with dehydration of the slab and flow of slab‐derived fluids along existing faults into the mantle wedge, that drives flux melting and accounts for the distinctive geochemical signatures and voluminous output of Ahi Tupua calderas.

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Toward Waveform‐Based Characterization of Slab & Mantle Wedge (SAM) Earthquakes

Cited by 2 publications

References 108 publications

Exploring the Nature and Influence of Intermediate-Depth Seismicity Beneath the Taupō Volcanic Zone

Exploring the Nature and Influence of Intermediate-Depth Seismicity Beneath the Taupō Volcanic Zone

Evidence From Intermediate‐Depth Earthquakes of Slab‐Derived Fluids Beneath the Taupō Volcanic Zone

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