Kosuke Heki

[1] The 2011 March 11 Tohoku-Oki earthquake (Mw9.0) caused vast damages to the country. Large events beneath dense observation networks could bring breakthroughs to seismology and geodynamics, and here I report one such finding. The Japanese dense network of Global Positioning System (GPS) detected clear precursory positive anomaly of ionospheric total electron content (TEC) around the focal region. It started ∼40 minutes before the earthquake and reached nearly ten percent of the background TEC

We use Global Positioning System (GPS) velocity data to model eastern Asian plate kinematics. Out of 15 stations in Korea, Russia, China, and Japan studied here, three sites considered to be on the stable interior of the hypothetical Amurian Plate showed eastward velocities as fast as ∼9–10 mm/yr with respect to the Eurasian Plate. They were stationary relative to each other to within 1 mm/yr, and these velocity vectors together with those of a few additional sites were used to accurately determ

Distinct periodic variations with annual frequencies are often found in the time series of continuous Global Positioning System (GPS) site coordinates in northeastern Japan. They show maximum arc-normal contraction of a few millimeters as well as maximum subsidence of 1 to 2 centimeters, both in March. In northeastern Japan, it snows heavily on the western flank of the backbone range, attaining a maximum depth of several meters in March. When observed snow depths were compared with the load dist

Surveys by continuous Global Positioning System in and around Japan revealed that the Amurian Plate collides with the North American Plate in central Japan by ∼2 cm/yr. Long‐term crustal deformation seems to be influenced mainly by this collision although subduction of oceanic plates governs short‐term elastic deformation over the arc. Here we study the long‐term deformation field by carefully removing the short‐term signals inferred from a‐priori plate convergence vectors and coupling strengths

Near‐field coseismic perturbations of ionospheric total electron content (TEC), caused by direct acoustic waves from focal regions, can be observed with Global Positioning System (GPS). They appear 10–15 min after the earthquake with typical periods of ∼4–5 min and propagate as fast as ∼1 km/s toward directions allowed by ambient geomagnetic fields. Ionospheric disturbance, associated with the 2004 December 26 great Sumatra‐Andaman earthquake, was recorded with nine continuous GPS receiving stat

The Japanese dense array of Global Positioning System recorded ionospheric disturbances as changes in Total Electron Content ∼12 minutes after the September 1 2004 eruption of the Asama Volcano, Central Japan. The disturbance had a period of one and a quarter minutes and propagated as fast as ∼1.1 km/s, suggesting its origin as the acoustic wave generated by the explosion. By comparing the disturbance amplitudes with those by a surface mine blast with a known energy, the overall Asama explosion

International audience

The first map of coseismic changes in gravity and geoid height has been drawn using the data from the Gravity Recovery and Climate Experiment (GRACE) satellites for the 2004 Sumatra‐Andaman earthquake. Here we present the second case of coseismic gravity change observation by satellite gravimetry, i.e., the change caused by an interplate thrust earthquake that occurred on 27 February, 2010 in Central Chile ( M w = 8.8). Gravity showed a negative jump with the largest drop of ∼5 μ gal on the back

Abstract Possible enhancement of ionospheric Total Electron Content (TEC) immediately before the 2011 Tohoku‐oki earthquake (M w 9.0) has been reported by Heki (2011). Critical responses to it often come in two stages; they first doubt the enhancement itself and attribute it to an artifact. Second (when they accept the enhancement), they doubt the significance of the enhancement among natural variability of space weather origin. For example, Kamogawa and Kakinami (2013) attributed the enhancemen

Global positioning system data show that about 20 slow‐slip events occurred during 1997–2007 in the southwestern part of the Ryukyu Arc, Japan, where large interplate thrust earthquakes are not known to have occurred in spite of relatively fast plate convergence. They recur fairly regularly on one patch of the subduction fault, which is as deep as 20–40 km and mechanically isolated in an uncoupled subduction zone. They have time constants of a month or so and release seismic moment equivalent of

Abstract Ionospheric electron enhancement was reported to have occurred ~40 min before the 2011 Tohoku‐oki ( M w 9.0) earthquake, Japan, by observing total electron content (TEC) with Global Navigation Satellite Systems receivers. Their reality has been repeatedly questioned due mainly to the ambiguity in the derivation of the reference TEC curves from which anomalies are defined. Here we propose a numerical approach, based on Akaike's information criterion, to detect positive breaks (sudden inc

The bulk of a tectonic plate is thought to move continously at a rate consistent with the geologic average. On the other hand, movements are highly episodic at plate boundaries. We study the plate dynamics that relate to these two different modes by modelling the displacements observed using the global positioning system in Northeast Iceland 1987–1990. These observations were made about 10 years after an episodic divergent movement between the North American and Eurasian plates 1975–1981. The ho

Three‐dimensional kinematic reference frame of geodetic very long baseline interferometry (VLBI) stations, tied to a geologic plate motion model, was established using the GLB907 solution by first selecting globally distributed stable plate interior stations and then applying a small translation and a rotation for the entire network in a three‐dimensional space so that the differences in the “horizontal” velocities between the VLBI observations and the model predictions are minimized. Since the