Utilizing online monitoring of water wells for detecting earthquake precursors

Abstract:

Groundwater reaction to earthquakes is well known and documented, mostly as changes in water levels or springs discharge, but also as changes in groundwater chemistry. During 2004 groundwater level undulations preceded a series of moderate (ML~5) earthquakes, which occurred along the Dead Sea Rift System (DSRS). In order to try and validate these preliminary observations monitoring of several observation wells was initiated. The monitoring and telemetry infrastructure as well as the wells were allocated specifically for the research by the Israeli National Water Company (Mekorot LTD.). Once several earthquake events were skipped due to insufficient sampling frequency and owing to insufficient storage capacity that caused loss of data, it was decided to establish an independent monitoring system. This current stage of research had commenced at 2011 and just recently became fully operative. At present there are four observation wells that are located along major faults, adjacent to the DSRS. The wells must be inactive and with a confined production layer. The wells are equipped with sensors for groundwter level, water conductivity and groundwater temperature measurements. The data acquisition and transfer resolution is of one minute and the dataset is being transferred through a GPRS network to a central database server. Since the start of the present research stage, most of the earthquakes recorded at the vicinity of the DSRS were smaller then ML 5, with groundwater response only after the ground movement. Nonetheless, distant earthquakes occurring as far as 300 km along a DSRS adjacent fault (ML~3), were noticed at the observation wells. A recent earthquake precursory reoccurrence was followed by a 5.5ML earthquake with an epicenter near the eastern shore of the Red Sea about 400km south to the wells that alerted the quake (see figure). In both wells anomalies is water levels and conductivity were found few hours before the quake, although any single anomaly cannot be regarded as a reliable precursor, cross-correlating several anomalies can indicate to an imminent earthquake, with high degree of certainty.