Interferometric Synthetic Aperture Radar (InSAR) can produce an image of detailed crustal deformation without any surface observation point. A SAR satellite, Sentinel-1, developed by the European Space Agency (ESA) has performed frequent observations of the same regions with C-band microwaves. In the present study, we investigate recent crustal deformations of two volcanic regions in Japan, i.e. Mt. Fuji and Izu-Oshima Island, using data acquired by Sentinel-1. First, a comparison of the InSAR time-series data (more than 20 times a year on average) with the Global Navigation Satellite System (GNSS) time-series data, at the coordinates of each GNSS station, confirmed close similarities between displacement rates (trends) of the InSAR and GNSS data around Mt. Fuji, although the InSAR data tend to include some apparent annual variation. Then, we applied a decomposition method to the InSAR data into two directions: East-West and Up-Down. For Mt. Fuji, the boundary where the direction of the displacement rates is changing, corresponds approximately to the strike of the dike in the subsurface. For Izu-Oshima Island, the data point out a faster deformation in the eastern part of the island, however, whether it is a true signal or not remains to be clarified.

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We perform numerical experiments simulating grain shear events in a fault zone based on a three-dimensional Distinct Element Method. We investigate the effects of initial arrangement of grains and intergranular frictional coefficient for the inertial number I around 10⁻³. We find that a variety of event modes, such as Riedel shear, depends on the initial arrangement. We further clarify that microscopic slip velocity of intermittent events does not simply correlate with the frictional coefficient.

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The present study detected pumice grains of Kawagodaira Pumice, which was erupted at 3160‒3137 cal BP, from the >0.063 mm size fraction of cored deposits of the Upper Holocene at site 3 of Nakazato, Yaizu City. We inferred the initial stratigraphic position of the pumice at a core depth of 6.51 m (elevation −3.70 m).

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Typhoon 21 (Lan) which occurred on 23 October 2017 and Typhoon 19 (Hagibis) on 12 October 2019 caused storm surges with sea-levels 0.5 m above the mean high tide mark in Ena Bay, Miura Peninsula, Kanagawa Prefecture, Japan. We surveyed the sediments before and after the storm surges at three sites in the lower intertidal zone and examined washed-up infaunal bivalves. These results lead to the following conclusions:
(1) Both typhoons caused sandy storm surge deposits which were up to 14 cm thick and characterized by graded structure and well-developed laminations;
(2) The primary sedimentary structure of the storm surge deposits disappeared by bioturbation within two years;
(3) The composition of the washed-up infaunal bivalve assemblage is quite similar for both typhoons, except for released Meretrix lamarcki, which is predominantly Mactra veneriformis, associated with Cyclina sinensis, and indicates >7 cm of erosion.

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Based on the field studies of the stratigraphy and geologic structures of the Lower Pleistocene Enrei Formation (Fm), we have re-evaluated the volcanic activity and tectonics of the Enrei Volcanic Field (EVF) in and around the Utsukushigahara area, Chu-Shin Highland, North Fossa Magna, central Japan. As well as in the other areas of EVF, the Enrei Fm in this area is mainly composed of lavas and pyroclastic rocks that filled up a collapse basin, about 6 km in NW-SE length and 3–5 km in NE-SW width, fringed by high-angled and irregularly-shaped abut-type unconformity surfaces on the Miocene basement rocks. The unconformity surfaces were originated by normal faultings with about 800 m vertical displacements. The volcanism here is approximately ranging in age between 2.1 and 1.3 Ma and is correlatable to the volcanism of the Older Enrei Fm in the other areas of EVF. In contrast with the mainly unimodal two-pyroxene andesitic volcanism in the other areas, the Enrei Fm here is characterized by the bimodal volcanism of two-pyroxene andesite and hornblende-bearing dacite in composition.The change of lithofacies and voluminous effusions of lavas and pyroclastic rocks on dry environments suggest that the Utsukushigahara area was situated in one of the volcanic centers of EVF. After the Early Pleistocene volcanism, the overall original near-horizontal structures have mostly been preserved until the present, except for the small scale faulting and gentle up-warping of the Miocene basement rocks and the overlying Enrei Fm in and around this area. This up-warping, that occurred probably during the latest Early to Middle Pleistocene, has been responsible for the rapid upheaval of the southern part of Chikuma Mountains to form the present-day Chu-Shin Highland. The volcanic/tectonic process of EVF is regarded as an example to form large-scale multiple cauldrons (calderas) in a back-arc region.

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