Lithospheric structure beneath Mt. Fuji inferred from grid search inversion of teleseismic receiver functions and surface wave dispersion
Abstract
The average eruption rate of Mt. Fuji has been much larger than most other island-arc volcanoes in Japan. The typical eruption product from an island-arc volcano is andesitic, while Mt. Fuji has erupted basaltic products. To understand the magma-plumbing system, we have to reveal the structure below Mt. Fuji. Even though the region around Mt. Fuji is a very active tectonic zone, the seismicity below Mt. Fuji is quiet, resulting in little knowledge about the structure of the Philippine Sea (PHS) Plate below Mt. Fuji. In this study, we estimate the structure below Mt. Fuji using a receiver function (RF) technique. This method is an effective tool in the seismic investigation of velocity gaps. First, we calculate RFs using multiple taper correlation (MTC) method and draw cross sections of the RF’s amplitude. Then, we perform grid search inversion and construct the detailed structure below Mt. Fuji. In the grid search inversion, we assume a simple structure model that has only six parameters v1, v2, v3, DA, DB and DC. DA, DB and DC are the boundary depths of sedimentary layer, upper crust and lower crust, respectively. We define the top velocity of sedimentary layer as v1, and v2 and v3 are the velocity of the upper crust and lower crust. The velocity structure in the sedimentary layer is linearly interpolated between v1 and v2. The conditions of constraint are as follows; we change v1, v2, v3 every 0.5 km/s and the parameter interval of DA, DB, DC is 1 km, and we fix vp/vs ratio as 1.73. In this way, we calculate 989472 synthetic waveforms using the propagator matrix method and RFs using MTC method. We sort out good velocity models from comparing these synthetic RFs to observed RFs. Then, we select a S velocity model that is consistent with surface wave dispersion models of Nishida et al., 2008. As a result, we find a high velocity boundary coming up from beneath the Moho-boundary of the surrounding PHS plate. The shape of this layer is similar to the low resistivity zone obtained from magnetotelluric data. We interpret this region as part of the magma- plumbing path of Mt. Fuji.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.T11C2102M
- Keywords:
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- 7218 SEISMOLOGY / Lithosphere;
- 8413 VOLCANOLOGY / Subduction zone processes