Experimental Evaluation of Initial Characteristics of DONET Pressure Sensors

摘要

The dense ocean floor network system for detecting earthquakes and tsunamis, DONET, began its operations in the Nankai Trough, southwest Japan, in 2010. The present study focuses on the pressure sensors used in DONET observatories to measure hydraulic pressure changes. Pressure sensors specify their performance for both hysteresis and repeatability; however, no details of the sensors' stability are currently available. It is known that pressure sensors typically show a drift in their readings over their operational life span. We evaluated the initial behavior of the pressure sensors before deployment into the deep sea by using our own high accuracy pressure standard. In our experiment, 20 MPa of hydrostatic pressure is applied to the pressure sensors under a constant temperature of 2 degrees C for a duration of 1 month. Our experiment suggests that the procedure is effective at clarifying the initial response and stability of the pressure sensors before deployment. It is proved that the repeatability of the initial response is well reproduced. Then the in situ measurements are processed and compared to the experimental measurements. The pressure sensors, to which a pressure equivalent to the deployed depth is applied, show that the sensor drift in the experiment corresponds in rate and direction to that from the in situ measurements.