5-9. Applications of GPS to Crustal Dynamics Research

 

    The Global Positioning System (GPS) is a powerful tool to monitor crustal deformations of a variety of scales. The technique has been widely used in Japan in various geodetic and geophysical researches. Earthquake Prediction Research Center of ERI serves as the headquarters of the Japanese University Consortium for GPS Research (JUNCO) to promote both domestic and international cooperative GPS projects. There are three major activities under this project; 1) Construction of GPS permanent array in the western Pacific and East Asia for monitoring plate motions and their interactions. This part of the project is cooperated with the Ocean Hemisphere Project (see 4-3)). 2) Monitoring the deformation process around the active faults and focal areas based on dense GPS arrays. Dense GPS array is indispensable for estimating slip distribution on the fault surface. For instance, post-seismic recovery of the 1995 Kobe earthquake was monitored with a dense GPS array. Also, a GPS array was used in the Ito area for imaging upward migration of dyke. 3) Other fundamental researches such as application of real-time kinematic survey and virtual reference station are.

In addition to the above major observational projects, numerical analyses using both JUNCO and nationwide network (GEONET of GSI) data have been promoted. An example shown in Fig. 1 is the stress increment in the recent three years estimated from GEONET data using a stress inversion method. This result delineates heterogeneity of the crust in terms of maximum shear stress. Its spatial variation is compared with shallow seismic activity of the same time period and the consistency between them is indicated.

Fig. 1: Distribution of maximum shear stress change rates over the Japanese islands derived from GEONET data.