To mitigate earthquake disasters

Research project for crustal activity based on the seismic data

Based on the use and maintenance of the seismograph networks, we have developd an advanced method for monitoring crustal activity in and around Japan. We also study the mechanisms of earthquakes.

New findings about crustal activities through monitoring

We have discovered new geophysical phenomena, deep low-frequency tremors, slow slip events, and repeating earthquakes. The monitoring system has been improved to immediately detect these activities and find other seismic phenomena.

Deep Low-frequency Tremor
Deep low-frequency tremors have been found above the ascending Philippine Sea plate in southwest Japan, and the configuration of these plates has been estimated from an analysis of the receiver function.

Left: Activity of deep low-frequency tremors and location of a slow-slip event in January, 2006. Sold triangles indicate Hi-net stations, shown in the right panel. Right: Tilt changes caused by the slow slip, observed in the northern Kii Peninsula and the Tokai district.

Repeating Earthquake
Earthquakes of the same size that occur repeatedly at the same locations have been found beneath the Kanto district. Most occur on the subductiong Philippine Sea plate.

Precise imaging of underground structure

Information about the underground structure is used to monitor crustal activity and model large earthquake processes. This information is imaged with high precision.

P-and S-wave velocity structures and attenuation structure (Qs), estimated using the tomographic method and data from the seismic wave's travel-time and amplitude.

P-and S-wave velocity structures and attenuation structure (Qs), estimated using the tomographic method and data from the seismic wave's travel-time and amplitude.

Ascending Philippine Sea plate imaged from an analysis of the receiver function.

Ascending Philippine Sea plate imaged from an analysis of the receiver function.

Modeling the process of a large earthquake

The property of asperity on the plate boundary and on the inland active major fault is clarified and a model of large earthquake process will be constructed using deterministic anc statistical approaches.

Slip property model on the plate boundary

Statistical analysis of seismic activity

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