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| Titel |
Seismic signature of crustal magma and fluid from deep seismic sounding data across Tengchong volcanic area |
| VerfasserIn |
Z. M. Bai, Z. Z. Zhang, C. Y. Wang, S. L. Klemperer |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062058
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| Zusammenfassung |
| The weakened lithosphere around eastern syntax of Tibet plateau has been revealed by the
Average Pn and Sn velocities, the 3D upper mantle velocity variations of P wave and S wave,
and the iimaging results of magnetotelluric data. Tengchong volcanic area is neighboring to
core of eastern syntax and famous for its springs, volcanic-geothermal activities and
remarkable seismicity in mainland China. To probe the deep environment for the Tengchong
volcanic-geothermal activity a deep seismic sounding (DSS) project was carried out across
the this area in 1999. In this paper the seismic signature of crustal magma and fluid is
explored from the DSS data with the seismic attribute fusion (SAF) technique, hence
four possible positions for magma generation together with some locations for
porous and fractured fluid beneath the Tengchong volcanic area were disclosed from
the final fusion image of multi seismic attributes. The adopted attributes include
the Vp, Vs and Vp/Vs results derived from a new inversion method based on the
No-Ray-Tomography technique, and the migrated instantaneous attributes of central
frequency, bandwidth and high frequency energy of pressure wave. Moreover, the
back-projected ones which are mainly consisted by the attenuation factor Qp , the delay-time
of shear wave splitting, and the amplitude ratio between S wave and P wave + S
wave were also considered in this fusion process. Our fusion image indicates such a
mechanism for the surface springs: a large amount of heat and the fluid released by the
crystallization of magma were transmitted upward into the fluid-filled rock, and the fluid
upwells along some pipeline since the high pressure in deep, thus the widespread
springs of Tengchong volcanic area were developed. Moreover, the fusion image,
regional volcanic and geothermal activities, and the seismicity suggest that the
main risk of volcanic eruption was concentrated to the south of Tengchong city,
especially around the shot point (SP) Tuantian. There are typical tectonic and deep
origin mechanisms for the moderate-strong earthquakes nearby SP Tuantian, and
precaution should be added on this area in case of the potential earthquake. Our fusion
image also clearly revealed that there exist two remarkable positions on the Moho
discontinuity through which the heat from the upper mantle was transmitted upward, and
this is attributed to the widely distributed hot material within the crust and upper
mantle.
We acknowledge the financial support of the Ministry of Land and Resources of China
(SinoProbe-02-02), and the National Nature Science Foundation of China (No. 41074033 and
No. 40830315).
Key Words: Seismic Signature, Magma, Tengchong Volcanic Area, Deep Seismic
Sounding, Seismic Attribute Fusion
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