Abstract: We re-investigated and analyzed the abnormal characteristics before Zhangbei earthquake (Jan. 1998, M_S6.2) and Ludian earthquake (Aug. 2014, M_S6.5), and studied the relationships between anomalies and three elements of earthquake prediction. It is suggested that the no-determinacy between anomalies and three elements of earthquake occurrence and the earthquake prediction will be very hard. According to the field observation and the tracking of epicenter development, we proposed directions and methods for improving and upgrading the ground fluid observation network. (1) Upgrade the basic observation network for field dynamic observations based on the existing stations after re-choose, which mainly includes physical and chemical items (water level, water temperature, radon, mercury, etc.), and the distance of each point is about 200 km in western region and 100 km in eastern region, especially 50 km around the capital. (2) In order to catch source anomaly and tracking the change process, design 5~6 regional observation networks with interval of about 50 km in the potential danger zones (Tianshan Mountain belt, China north-south earthquake belt, Tancheng-Lujiang seismic zone, etc.). Try to explore the short-term earthquake prediction methods based on these networks. (3) Attention should be paid to three key technologies when we construct the two levels network: improving the digital observation technology, optimizing the observational borehole in inherent quality, and developing non-mainstream observation items (gas, ion, flow, etc.).

Key words: Underground fluid, Optimizing and upgrading in observation network, National basic observation network, Regional observation network