With the increasing of extreme rainfall frequency, landslides accompanied by mudslides often lead to serious casualties and property damage. On 3rd July 2021, a debris flow occurred in Izu Mountain area, Shizuoka Coun...With the increasing of extreme rainfall frequency, landslides accompanied by mudslides often lead to serious casualties and property damage. On 3rd July 2021, a debris flow occurred in Izu Mountain area, Shizuoka County, Japan, and then resulted in 26 deaths and 131 houses destroyed, where houses were mainly built along the banks of the creek. In order to analyse the landslide state and distribution, a two-dimensional debris flow dynamic model(Massflow) was selected to simulate the process of the landslide-generated debris flow. When the model results are considered together with remote sensing images, the volume distribution of the unstable landslide is also able to be determined. The results show that(1) the affected areas are mainly concentrated at the outfall of the gully and on both sides of the streets.(2) The pore pressure ratio is an important factor affecting the damage range of this debris flow.(3) The increase of the pore pressure ratio in the landslide make the movement distance of debris flow increase significantly.展开更多
Digital waveform data recorded by the vertical component short period stations at the American networks of SCSN, NCSN and PNSN and three components broadband stations at the Germany and Swiss networks and arrays of GR...Digital waveform data recorded by the vertical component short period stations at the American networks of SCSN, NCSN and PNSN and three components broadband stations at the Germany and Swiss networks and arrays of GRFN, GRSN and SDSNet for the events between 1981 and 2000 under Izu-Bonin are used as data sets. The N-th root slant stack method was used to pick up the SdP phase converted at the velocity interface beneath source and the regionalized difference of the 660 km discontinuity beneath Izu-Bonin is studied. It is found that while the dip angles of the subducting slab and the maximal depths of sources increase gradually from 35N to 26N, the 660 km discontinuity appears regionalized differences. The discontinuity exists at 660 km while there is no effect from subducting slab, but it is depressed to the depth of 720 km while there are obvious effects. The dispersion of converted points is still an unsolved problem which maybe result from the complex structure of the discontinuity, converted phases which were misjudged, or the assumption of one dimensional spherical earth model.展开更多
The SdP, pdP and sdP phases are picked up with the Nth root slant stack method from the digital waveform data recorded by the networks and arrays in USA, Germany and Switzerland for the earthquakes occurring beneath I...The SdP, pdP and sdP phases are picked up with the Nth root slant stack method from the digital waveform data recorded by the networks and arrays in USA, Germany and Switzerland for the earthquakes occurring beneath Izu-Bonin and Japan Sea. The mantle discontinuities and the effects of subducting slab on the 660 km and 410 km discontinuities are studied. It is found that there are mantle discontinuities existing at the depths of 170, 220, 300, 410, 660, 850 and 1150 km. Beneath Izu-Bonin, the 410 km discontinuity is elevated, while the 660 km discontinuity is depressed; for both discontinuities, there are regionalized differences. Beneath Japan Sea, however, there is no depth variation of the 410 km discontinuity, and the 660 km discontinuity is depressed without obvious effect of the subducting slab.展开更多
基金supported by the National Key Research and Development of China(No.2019YFC1510603)National Natural Science Foundation of China(No.51639007)。
文摘With the increasing of extreme rainfall frequency, landslides accompanied by mudslides often lead to serious casualties and property damage. On 3rd July 2021, a debris flow occurred in Izu Mountain area, Shizuoka County, Japan, and then resulted in 26 deaths and 131 houses destroyed, where houses were mainly built along the banks of the creek. In order to analyse the landslide state and distribution, a two-dimensional debris flow dynamic model(Massflow) was selected to simulate the process of the landslide-generated debris flow. When the model results are considered together with remote sensing images, the volume distribution of the unstable landslide is also able to be determined. The results show that(1) the affected areas are mainly concentrated at the outfall of the gully and on both sides of the streets.(2) The pore pressure ratio is an important factor affecting the damage range of this debris flow.(3) The increase of the pore pressure ratio in the landslide make the movement distance of debris flow increase significantly.
基金State Natural Science Foundation of China (49874020) and the Special Funds for Major State Basic Research of China (95-13-04-06).
文摘Digital waveform data recorded by the vertical component short period stations at the American networks of SCSN, NCSN and PNSN and three components broadband stations at the Germany and Swiss networks and arrays of GRFN, GRSN and SDSNet for the events between 1981 and 2000 under Izu-Bonin are used as data sets. The N-th root slant stack method was used to pick up the SdP phase converted at the velocity interface beneath source and the regionalized difference of the 660 km discontinuity beneath Izu-Bonin is studied. It is found that while the dip angles of the subducting slab and the maximal depths of sources increase gradually from 35N to 26N, the 660 km discontinuity appears regionalized differences. The discontinuity exists at 660 km while there is no effect from subducting slab, but it is depressed to the depth of 720 km while there are obvious effects. The dispersion of converted points is still an unsolved problem which maybe result from the complex structure of the discontinuity, converted phases which were misjudged, or the assumption of one dimensional spherical earth model.
基金the National Natural Science Foundation of China(Grant No.49874020) the Ph D Programs Foundation of Ministry of Education of China(Grant No.99000108).
文摘The SdP, pdP and sdP phases are picked up with the Nth root slant stack method from the digital waveform data recorded by the networks and arrays in USA, Germany and Switzerland for the earthquakes occurring beneath Izu-Bonin and Japan Sea. The mantle discontinuities and the effects of subducting slab on the 660 km and 410 km discontinuities are studied. It is found that there are mantle discontinuities existing at the depths of 170, 220, 300, 410, 660, 850 and 1150 km. Beneath Izu-Bonin, the 410 km discontinuity is elevated, while the 660 km discontinuity is depressed; for both discontinuities, there are regionalized differences. Beneath Japan Sea, however, there is no depth variation of the 410 km discontinuity, and the 660 km discontinuity is depressed without obvious effect of the subducting slab.
