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Observation network


Seismic Underground Water Observation Network

Seismic Underground Water Observation Network

Seismic Underground Water Observation Network Under the Inter-ministerial Major Science and Technology Research Program of 'Earthquake and Active Fault Research' of the National Science Council, Executive Yuan, the Central Weather Bureau (CWB) conducts joint research on the relativity of underground water level change and seismic precursor with the 'Underground Water Level Abnormality before and after Earthquake Research Program' by Water Resources Agency, Ministry of Economic Affairs. By the end of 2005, 16 observation wells have been established consecutively to observe the relativities between the atmospheric pressure, precipitation, water temperature, temperature and he underground water level by continuous records to set up the underground water level change-related parameters. Meanwhile, conduct the integrated research with CWB's 'GPS Crust Deformation Consecutive Observation Program' to understand the relativity between earthquake and seismic activities with a view to mastering the seismic precursor judgment and laying the foundation for earthquake prevention. The factors affecting the underground water level change include component ones and non-component ones (underground current, atmospheric pressure, precipitation and artificial supply). The effects of non-component factors such as artificial supply can be avoided by selecting appropriate observation wells while more conspicuous changes of factors such as underground current, atmospheric pressure and precipitation shall be deducted by calculations of theoretical values and observation values. The rest earthquake-related component factors are the reaction of tectonic stress-caused changes of rock volume leading to the water pressure changes in the pore gaps, and further reflecting the underground water level change of the aquifer layer. When the rocks are pressured by the tectonic stress before the re-activities of the major damaging layer or major fault, slight cracks will be developed, resulting in the changes of the pore rate and penetration rate of the rocks. And the underground water level of the rock layer will tend to increase along with the stress, therefore observation of the abnormal changes of the underground water level will be helpful to understand earthquake precursors. To monitor the real time changes of the underground water level, CWB started in March, 2004 to transmit the real time underground water level data of Hualien Weather Station via digital cable to CWB for real time judgment and abnormity detection by underground water receiving and real time presentation programs. And gradually set up since January, 2005 three underground water real time observation stations in Yilan County Chuangwei Elementary School, Tainan County Naba Elementary School, and Tainan County Liujia Elementary School. In January, 2006, establish two underground water real time observation stations in Yunlin County Tunghe Elementary School and Pingtung County Chishan Elementary School (Figure 1). The water level data of various observation stations in sampling rate of 1Hz are transmitted in real time to the Seismological Center. In addition, adjust and remove the water level change as a result of factors such as precipitation and air pressure. Meanwhile, data of real time precipitation of the precipitation observation stations under CWB are transmitted. Air pressure instruments are established in various observation stations to transmit data of real time air pressure. As far as the currently obtained underground water level data are concerned, records of earthquake, resulting deformations and the remote quake surface wave are excellent. In particular, records in the Hualien Weather Station are very good, indicating the good enclosure of underground water observation well and good sensitivity to the crustal reactions. The current data process is to make analysis of the non-component factors of influence based on the recording data from various observation stations with a view to more effective understanding of reactions before earthquake or due to earthquake after removing the influences of non-component factors. Figure 1 Locations of CWB Seismological Center Seismic Underground Water Observation Stations.