Results of GEONET real-time analysis
Basara Miyahara(basara@gsi.go.jp), Takuya Nishimura: 

Geographical Survey Institute (GSI), Japan operates a nationwide GPS 
observation array, GEONET. About 1,220 GEONET stations are equipped 
with a real-time data transmission and a high sampling rate mode. 
GSI processes the GPS data routinely, not in real time, in order 
to provide location information for the public and to monitor 
crustal movement. To monitor crustal movements, it is better to 
process all the data in real time. However, the data streaming from 
the stations are too huge to process together in real-time. Therefore, 
we set up small clusters with limited number of stations and process 
kinematic GPS in both real-time and post-processing mode when volcanoes 
become active or earthquakes occur. 

The post-processing analysis detected over 80cm horizontal displacement 
with the 2003 M8.0 Tokachi-oki earthquake. In addition, we detected 
smaller displacement for several M~7 earthquakes.
 We are planning to develop the system for near real-time post-processing 
analysis and to estimate an earthquake fault model utilizing the earthquake 
early warning service by JMA (Japan Meteorological Agency). Using an 
earthquake information including occurrence time, magnitude, and location 
helps us to detect the coseismic displacement from noisy results of kinematic 
GPS.  In the case of the 2004 M6.8 Chuetsu earthquake, estimation of 
earthquake source fault model with near real-time post-processing takes 
about 50 minutes and well consistent with a result form GEONET routine analysis.