Satellite magnetic anomalies over subduction zones: The Aleutian Arc anomaly

Clark, Sherren C.; Frey, Herbert; Thomas, H. H.

doi:10.1029/gl012i001p00041

Cited by 32 publications

(20 citation statements)

References 12 publications

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“…Once again, the base model has a weak signal along the trend of the subduction boundary with the opposite sign to that observed in the MF7 anomaly map. The spur visible in the observations north of the boundary is thought to be a result of earlier subduction, dating from before 60 Ma (Clark et al, ).…”

Section: Resultsmentioning

confidence: 99%

Origin of Long‐Wavelength Magnetic Anomalies at Subduction Zones

Williams

Gubbins

2019

JGR Solid Earth

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Most subduction zones have associated long‐wavelength anomalies in the lithospheric magnetic field observed at satellite altitude. We model the 13 subduction zones defined by seismicity and seismic tomography using vertically integrated magnetizations that are increasing, level, or decreasing away from the trench. These mimic end members of a magnetized mantle wedge, a uniform layer, and a magnetized dipping lithospheric slab. They are added to a global model of vertically integrated magnetization based on continental and oceanic geology. We find the dipping slab places the anomaly too close to the trench, while the other two fit the data equally well and use the level model in the main part of the study. Anomalies at the Sunda, Aleutians, Cascadia, Central American, and Kamchatka‐Japan zones are well modeled by uniform magnetization of differing susceptibilities and spatial extents. We show the South American anomaly is weak because the magnetization lies mainly in the null space that produces no external potential magnetic field. There is no anomaly associated with the Ryukyu system, possibly because the present subduction started too recently for magnetization to have formed. The magnetic anomaly stretching down the Baja California peninsula is not present in the prediction because there is no seismicity on which to base a slab geometry, but recent tomography suggests a fossil slab there and we propose historic subduction as the origin of the Baja magnetic anomaly. Finally, we discuss the mineralogical origins of the magnetization and favor serpentinization of the region above the subducted plate.

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Section: Resultsmentioning

confidence: 99%

Origin of Long‐Wavelength Magnetic Anomalies at Subduction Zones

Williams

Gubbins

2019

JGR Solid Earth

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“…• C) and surrounding non-magnetic mantle (Clark et al, 1985;Vasicek et al, 1988). The setting of the 550…”

Section: Configuration Of the Plate Interfacementioning

confidence: 99%

Propagation of the 2001–2002 silent earthquake and interplate coupling in the Oaxaca subduction zone, Mexico

et al. 2005

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The aseismic slow slip event of [2001][2002] in Guerrero, Mexico, with an equivalent magnitude M W ∼ 7.5, is the largest silent earthquake (SQ) among many recently recorded by GPS in different subduction zones (i.e. Japan, Alaska, Cascadia, New Zealand). The sub-horizontal and shallow plate interface in Central Mexico is responsible for specific conditions for the ∼100 km long extended transient zone where the SQs develop from ∼80 to ∼190 km inland from the trench. This wide transient zone and relatively large slow slips of 10 to 20 cm displacements on the subduction fault result in noticeable surface displacements of 5-6 cm during the SQs. Continuous GPS stations allow one to trace the propagation of SQs, and to estimate their arrival time, duration and geometric attenuation. These propagation parameters must be accounted in order to locate source of slow slips events and to understand the triggering effect that they have on large subduction earthquakes. We use longbaseline tiltmeter data to define new time limits This modeling shows that the SQ ceased gradually in the central part of the Oaxaca segment of the subduction zone (west of Puerto Angel, PUAN) and then it apparently triggered another SQ in SE Oaxaca (between PUAN and Salina Cruz, SACR). The estimated horizontal velocities for inter-event epochs at each GPS site are used to assess an average interplate coupling in the Central Oaxaca subduction zone.

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“…The predicted anomaly map is free of such contaminations and thus helps to distinguish anomaly features over the C-O boundary. There are also anomaly features over the oceans, flanked by Phanerozoic con- tinental regions, which are due to either, subduction zones, viz., Aleutian arc (Clark et al, 1985) in the northern Pacific region, and southwest coast of Mexico (Counil and Achache, 1987) or with oceanic plateaus, especially off the eastern coast of Australia and southern coast of Africa. The strong negative anomaly features over the Labrador Sea, situated between Greenland and the North American craton, could be a result of higher VIS value on both sides of the continents as compared to the smaller value of the Labrador Sea (Bradley and Frey, 1991).…”

Section: Preliminary Resultsmentioning

confidence: 99%