Source and path of magma for volcanoes in the subduction zone of northeastern Japan

Wyss, Max; Hasegawa, Akira; Nakajima, Jun

doi:10.1029/2000gl012558

Cited by 69 publications

(59 citation statements)

References 32 publications

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“…This observation is consistent with the dehydration embrittlement hypothesis for intra-slab seismicity beneath NE Japan. A recent study on the b-value mapping down to a depth of 150 km within the subducting slab beneath NE Japan revealed high-b values in the slab, which are caused by the presence of fluids supplied by dehydration reactions of the minerals in the slab [Wyss et al, 2001]. Dehydration of the subducting oceanic crust increases pore-pressure, lowering the effective stress and thus increasing the b-value of the frequency-magnitude distribution [Scholz, 1968;Schorlemmer et al, 2003].…”

Section: Resultsmentioning

confidence: 99%

Seismic evidence for dehydration embrittlement of the subducting Pacific slab

Mishra

Zhao

2004

Geophysical Research Letters

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[1] We determined a fine 3-D P-wave velocity structure of the subducting Pacific slab by inverting a large number of high-quality P-arrival times to better understand the genesis of the 26 May 2003 Miyagi-oki earthquake (Mw 7.0) and its aftershock sequence, which occurred within the subducting Pacific slab beneath northeast (NE) Japan. Lateral and depth-ward heterogeneities are imaged up to several tens of kilometers beneath the upper boundary of the subducting slab. The main shock and its aftershocks occurred in a distinct zone characterized by a lower velocity anomaly than its surroundings within the slab. The reduced velocity anomaly within the slab is attributed to the process of dehydration embrittlement resulting from the dehydration of hydrous minerals in the subducting Pacific slab, which may have induced the main shock and its aftershock sequence by enhancing pore pressures along the pre-existing faults/fractures in the subducting slab beneath the NE Japan forearc region.

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Section: Resultsmentioning

confidence: 99%

Seismic evidence for dehydration embrittlement of the subducting Pacific slab

Mishra

Zhao

2004

Geophysical Research Letters

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“…Schorlemmer et al [2003] interpreted a high b value anomaly 90-200 km below the Aeolian volcanic district as related with the origin of the magma. The study of Wyss et al [2001] compares b value analysis of microseismicity with published results of seismic body wave tomography for the Tohoku region, suggesting that the b value anomaly at 150 km is connected to a low S wave velocity anomaly originating at that depth. This would suggest that, in fact, magma genesis takes places at greater depth, and the magma travels a curved path through the mantle wedge.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, melts or aqueous fluids will penetrate upward into the crust of the overlying plate. Depending on mantle wedge dynamics, these melts may either flow vertically or be deviated by mantle wedge flow [Wyss et al, 2001;Manea et al, 2005]. Direct geophysical evidence for slab dehydration at depth beneath arc volcanoes and its relation to melt in the mantle wedges and fluid conduits through the overriding lithosphere, however, remain sparse.…”

Section: Introductionmentioning

confidence: 99%

“…Wiemer and Benoit [1996] found significant changes in b value at depths of 90-100 km on the upper side of the WBZ in New Zealand, Cook Inlet, and the Shumagin Island region. Wyss et al [2001] found a high b value at 150 km depth in the subduction zone beneath the Tohoku area (northern Japan). Schorlemmer et al [2003] interpreted a high b value anomaly 90-200 km below the Aeolian volcanic district as related with the origin of the magma.…”

Section: Introductionmentioning

confidence: 99%

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Magmatic processes in the Alaska subduction zone by combined 3‐D b value imaging and targeted seismic tomography

et al. 2009

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[1] We combine two complementary seismological methods to study the deep roots of arc volcanism in the Alaskan subduction zone: targeted seismic body wave tomography and imaging of the relative size distribution (b value) of earthquakes. For the tomography we apply a staggered inversion scheme, starting with the minimum 1-D velocity model, progressing to a 3-D velocity model. Inversions are based on traveltime data from about 5500 events with approximately 100,000 P and 50,000 S high-quality arrivals, allowing us to resolve the 3-D velocity field on a 20 Â 20 km grid. For the b value imaging we have introduced a new 3-D sampling approach to map the b values on surfaces in the Wadati-Benioff zone (WBZ). Our b value study is based on 12,474 relocated events of magnitude of completeness !2.4 and depth >40 km. We observe anomalously high b values at depths around 100 km, appearing locally concentrated beneath active subduction volcanoes. We believe that these zones are associated with dehydration of the slab and subsequent magma generation. The analysis of V P /V S ratios likewise shows indications of the presence of fluids: significantly higher V P /V S ratios rising in columns from the top of the WBZ at 100 km depth below active volcanic centers. On the basis of the joint interpretation, we propose that our images track fluids from their genesis at 100 km depth at the top of the subducting plate to the bottom of the crust below volcanoes.Citation: van Stiphout, T., E. Kissling, S. Wiemer, and N. Ruppert (2009), Magmatic processes in the Alaska subduction zone by combined 3-D b value imaging and targeted seismic tomography,

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“…The b-value in the present study has been estimated by maximumlikelihood method (Bender 1983) (Wiemer et al 1998), Montserrat (Power et al 1998), Etna (Murru et al 1999), Katmai (Jolly and McNutt 1999) and East rift zone of Kilauea (Wyss et al 2001).…”

Section: Variations In Spatio-temporal B-valuesmentioning

confidence: 99%

Incipient status of dyke intrusion in top crust – evidences from the Al-Ays 2009 earthquake swarm, Harrat Lunayyir, SW Saudi Arabia

Mukhopadhyay

Mogren

Mukhopadhyay

et al. 2013

Geomatics, Natural Hazards and Risk

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The 2009 earthquake-swarm in the Al-Ays volcanic zone in Harrat-Lunayyir in NW Saudi-Arabia is unique because of its intense character and focal-depth distribution at two depth bands (5-10 and 15-20 km) in upper crust without volcanic eruption. We investigate an anatomy of the dyke-intrusion model that supports the mechanism for the swarm itself with seismotectonics, pore pressure diffusion process and inference model. Inferred dyke-intrusion initially started at depth had a five-day peak period (15-20 May 2009) since inception of eventrecordings, following which the activity diminished. The process of pore pressure perturbation and resultant ''r-t plot'' with modelled diffusivity (D ¼ 0.01) relates the diffusion of pore pressure to seismic sequence in a fractured poro-elastic fluidsaturated medium. The spatio-temporal b-values show high b-values (41.3) along the zone of dyke intrusion (length 10 km and height 5 km) at *20km depth. The main-shock and other prominent earthquakes originated on a moderate b-value zone (*1.0). Temporal b-value analysis indicates an exceptionally low b-value (*0.4) during the main-shock occurrence. The AlAys lava-field is inferred to underlie a seismic volume trending NW-SE bounded on both sides by two NW-SE trending fault systems, dipping 40-508 opposite to each other within a proposed nascent rift setting.

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Source and path of magma for volcanoes in the subduction zone of northeastern Japan

Cited by 69 publications

References 32 publications

Seismic evidence for dehydration embrittlement of the subducting Pacific slab

Seismic evidence for dehydration embrittlement of the subducting Pacific slab

Magmatic processes in the Alaska subduction zone by combined 3‐D b value imaging and targeted seismic tomography

Incipient status of dyke intrusion in top crust – evidences from the Al-Ays 2009 earthquake swarm, Harrat Lunayyir, SW Saudi Arabia

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