HR: 0800h
AN: V21A-0595    [Abstracts]
TI: Effective Elastic Thickness Beneath the Japanese Islands, and its Relationship to Seismogenic Layer and Magnetic Crustal Thickness
AU: * Tanaka, A
EM: akiko-tanaka@aist.go.jp
AF: Geological Survey of Japan, AIST, AIST Tsukuba Central 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AU: Nakano, T
EM: tsukasa.nakano@aist.go.jp
AF: Geological Survey of Japan, AIST, AIST Tsukuba Central 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AB: We estimated `lithospheric` thicknesses from different sources. The effective elastic thickness of the lithosphere (Te) is estimated from the coherence between Bouguer gravity and topography. Te reflects the integrated brittle, elastic and ductile strength of the lithosphere over geological time scales, and depends on many geophysical properties, such as thermal structure, crustal composition, and plate geometry. The bottom depth of the magnetized crust (Zb), Curie-isotherm depth, determined from the spectral analysis of residual magnetic anomalies, is interpreted as a proxy for lithospheric thermal structure. Local maximum depth of earthquakes (D₉₀), defined as the depth above which 90% of the earthquakes occur, is interpreted to mark the onset of plastic behavior. We showed spatial distributions of these three kinds of `lithospheric` thicknesses in square windows of 2.125^o x 2.125^o beneath the Japanese Islands. These values represent the average values over a wide area and may not characterize detailed lithospheric structure, while these spatial variations show similar trends. Because both Te and D₉₀ are indicative of strength, variations in Te correlate with those in D₉₀, both of them having similar values, although Te is usually smaller than D₉₀. On the other hand Zb provides information on the thermal properties of the lithosphere, both variations in Te and D₉₀ are broadly correlated with those in Zb. These values may have the potential to provide information on mechanical and thermal properties beneath the Japanese Islands.
DE: 1236 Rheology of the lithosphere and mantle (7218, 8160)
DE: 7218 Lithosphere (1236)
DE: 8031 Rheology: crust and lithosphere (8159)
DE: 8138 Lithospheric flexure
DE: 8159 Rheology: crust and lithosphere (8031)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005