Takuya Nishimura 교수

Temporal change of deformation in northeastern Japan is clarified by continuous Global Positioning System (GPS) observations from 1995 April to 2002 March. The observed GPS velocity is approximately parallel to the direction of plate convergence on east and west plate boundaries of northeastern Japan and shows post-seismic transient deformation around source regions of the M w 7.8 1993 Hokkaido-Nansei-Oki and the M w 7.7 1994 Sanriku-Haruka-Oki earthquakes. We interpret the source of the observe

Abstract We detected short‐term slow slip events (SSEs) previously observable only with tilt and strain data along the Nankai Trough, southwest Japan, using GNSS (Global Navigation Satellite System) data. Offsets detected in GNSS time series using Akaike's information criterion helped automatically identify 207 episodes with a motion direction opposite to that of the relative plate motion from June 1996 to January 2012. By nonlinear inversion of the detected displacement, we estimated rectangula

In this study, short-term slow slip events (SSEs) along the Ryukyu Trench, southwestern Japan were systematically examined using continuous global navigation satellite system (GNSS) data. In total, 130 probable and 93 possible short-term SSEs in the moment magnitude (M w ) range of 5.6 to 6.8 were identified from January 1997 to November 2013 by GNSS time series offset monitoring and elastic dislocation modeling with a rectangular fault located on the subducting Philippine Sea Plate. The detecte

Intense crustal activity including earthquake swarms, eruptions, and a caldera formation in the northern Izu Islands started on June 26, 2000, accompanied with large crustal deformation. Permanent GPS data reveals the spatial pattern and time evolution of ground deformation. The observations reveal shrinking and subsidence of Miyakejima and extension between Kouzushima and Niijima. We constructed a source model to explain the observed displacements during the period between June 26 and the end o

Southwest Japan is located in the subduction margin between the continental Amurian and oceanic Philippine Sea plates. Recent land GNSS (Global Navigation Satellite System) and offshore Global Positioning System-Acoustic geodetic measurements were used to clarify the deformation in and around these plate margins. We examined strain partitioning and interplate coupling using a block modeling approach on the observed velocities. Although the main plate boundaries are the Nankai Trough and Sagami t

We have modeled the broad postseismic uplift measured by geodetic leveling in the epicentral area of the 1959 M w = 7.3 Hebgen Lake, Montana earthquake, a normal faulting event in the northern Basin and Range province. To fit the observed uplift we calculate synthetic postseismic deformation using the relaxation response of a gravitational viscoelastic Earth to the earthquake. For a model with an elastic plate overlying a viscoelastic half‐space, we find that the elastic thickness is 38 ± 8 km,

Since November 30, 2020, an intense seismic swarm and transient deformation have been continuously observed in the Noto Peninsula, central Japan, which is a non-volcanic/geothermal area far from major plate boundaries. We modeled transient deformation based on a combined analysis of multiple Global Navigation Satellite System (GNSS) observation networks, including one operated by a private sector company (SoftBank Corp.), relocated earthquake hypocenters, and tectonic settings. Our analysis show

The large displacement induced by the 2011 M 9.0 off the Pacific coast of Tohoku Earthquake was observed by GPS stations of the permanent GPS Earth Observation Network system (GEONET) in northeastern Japan. The displacement was characterized by the eastward displacement and subsidence in the Pacific coastal area. The horizontal displacement exceeded 5.3 m, which is the largest ever detected by GEONET. The mainshock was followed by a sequence of aftershocks. We processed the GPS data through a ki

We clarify the contemporary deformation observed by GPS and leveling for the greater Tokyo (Kanto, eastern Tokai, and the Izu islands) region, where the Izu‐Ogasawara (Bonin) arc is subducting and colliding with the central part of the Japan arc. From these data, we develop a kinematic model of fault sources with variable components of seismic and aseismic slip. Under the assumption that the contemporary deformation during 1995–2000 is representative of the long‐term interseismic strain field, t

The 2011 Tohoku-oki earthquake caused large eastward displacement and subsidence along the Pacific coast of northeastern Japan. This earthquake partly solved a well-known paradox holding that sense and rate of deformation differ greatly between geologic and geodetic estimates. A paradox remains, however, in explaining long-term uplift along the Pacific coast on a geologic time-scale. Geodetic data show that coastal subsidence continued at a nearly constant rate of ∼5 mm/yr with small fluctuation

Ground uplift and earthquake swarm activity has continued around Mt. Iwate volcano, northern Japan, since February 1998. On September 3, 1998 a M6.1 earthquake occurred southwest of the volcano. Satellite radar interferometry acquired by JERS‐1 reveals volcanic and coseismic deformation to the west of the summit, which is concordant with displacements observed by GPS. We analyzed geodetic observations including InSAR, GPS, and EDM to model the source of the surface deformation. The inferred mode

Abstract Slow slip events (SSEs) along subduction zones play an important role in accommodating relative plate motion. SSEs interplay with large megathrust earthquakes and other slow earthquakes, including low frequency and very low frequency earthquakes. The Kanto and Tokai regions of central Japan host frequent slow and large earthquakes, with significant differences in slip behavior along the subduction zones in the Suruga Trough, Sagami Trough, and Japan Trench. In this study, we conducted a

The interferometric analysis using ALOS SAR data allows us to map the detailed spatial pattern of the deformation associated with the 2007 M6.8 Niigataken Chuetsu‐oki earthquake. The interferograms reveal not only a large deformation near the source area of the earthquake but also a local uplift in the region of active folding, 15 km east of the earthquake epicenter. The 1.5‐km‐wide and 15‐km‐long band of uplift is located along the anticline axis of an active fold and cannot be explained by the