caa a22 4500 463172353 CHVBK 20180406164817.0 cr unu---uuuuu 170326e20070401xx s 000 0 eng 10.1007/s10950-007-9049-z doi (NATIONALLICENCE)springer-10.1007/s10950-007-9049-z Topography of the Moho and Conrad discontinuities in the Kyushu district, Southwest Japan [Elektronische Daten] [Hitoshi Oda, Takashi Ushio] The first P-arrival time data from local earthquakes are inverted for two-dimensional variation of the depths to the Conrad and Moho discontinuities in the Kyushu district, southwest Japan. At the same time, earthquake hypocenters and station corrections are determined from the data. The depths to the discontinuities are estimated by minimizing the travel time residuals of first P-arrival phases for 608 earthquakes observed at 57 seismic stations. In the land area of Kyushu, the Conrad and Moho discontinuities are located within the depth ranges of 16-18 and 34-40km, respectively. The Conrad discontinuity is not as largely undulated as the Moho discontinuity. The depth to the Moho is deep along the east coast of Kyushu, and the deepest Moho is closely related to markedly low velocity of P wave. We regard the deepest Moho as reflecting the Kyushu-Palau ridge subducting beneath the Kyushu district, together with the Philippine Sea slab. In western Kyushu, the shallow Moho is spreading in the north-northeast-south-southwest direction in the Okinawa trough region. Based on the presence of low-velocity anomaly in three-dimensional velocity structure and seismogenic stress field of shallow crustal earthquakes, the shallow Moho is interpreted as being due to lower crustal erosion associated with a small-scale mantle upwelling in the Okinawa trough region. The velocity discontinuity undulation basically has insignificant effect on hypocenter determination of the local earthquakes, but the Moho topography makes changes in focal depths of some upper mantle earthquakes. The depth variation of the Moho discontinuity has a good correlation with the Bouguer gravity anomaly map; i.e., the shallow Moho of western Kyushu and the deep Moho of eastern Kyushu closely correlate with the positive and negative Bouguer gravity anomalies, respectively. Springer Science+Business Media, Inc., 2007 Conrad and Moho discontinuities nationallicence Bouguer gravity anomaly nationallicence Three-dimensional velocity structure nationallicence Philippine Sea slab nationallicence Kyushu district nationallicence Southwest Japan nationallicence Oda Hitoshi Department of Earth Sciences, Okayama University, 700-8530, Okayama, Japan aut Ushio Takashi Department of Earth Sciences, Okayama University, 700-8530, Okayama, Japan aut Journal of Seismology Kluwer Academic Publishers 11/2(2007-04-01), 221-233 1383-4649 11:2<221 2007 11 10950 https://doi.org/10.1007/s10950-007-9049-z text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10950-007-9049-z text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Oda Hitoshi Department of Earth Sciences, Okayama University, 700-8530, Okayama, Japan aut NATIONALLICENCE 700 1- Ushio Takashi Department of Earth Sciences, Okayama University, 700-8530, Okayama, Japan aut NATIONALLICENCE 773 0- Journal of Seismology Kluwer Academic Publishers 11/2(2007-04-01), 221-233 1383-4649 11:2<221 2007 11 10950 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer