China's component borehole strainmeter network

In 2004, China's digital seismic observation network project began to deploy 40 sets YRY-4 four-component borehole strainmeters in order to monitor earthquake preparation process. The paper describes observed solid tidal strain discreteness and tidal factor anisotropy, analyzes the reliability of observational data and discusses the cause for this phenomenon. After getting rid of interferences, the network, in two years practice, has observed several pre-seismic strain anomalies at stations close to epicenters especially in the Wenchuan <i<M</i<<sub<S</sub<8.0 megaquake. It shows that this borehole strainmeter network is capable of monitoring seismogenic process.