5:15 PM - 7:15 PM
[HSC06-P07] Simultaneous gravity measurements using two superconducting gravimeters to evaluate their applicability for monitoring CO2 geological storage
Keywords:Gravity measurements, Superconducting gravimeters, CO2 geological storage
Gravimetry is used to monitor the distribution and migration of carbon dioxide (CO2) injected into geological formations. To detect gravity signals of interest, it is necessary to remove noise as accurately as possible, as this determines its feasibility for CO2 geological storage monitoring. A promising noise reduction approach is to eliminate common-mode noise by taking the difference between gravity changes measured simultaneously using two gravimeters installed close together. In this study, we evaluate the applicability of gravity difference measurements to CO2 geological storage monitoring by analyzing long-term gravity difference time series data from two superconducting gravimeters installed in the coastal area of Tomakomai, Hokkaido. The six-year time series exhibited an almost linear trend, despite the presence of higher-frequency noise. Linear regression of the time series yielded a linear component of 0.44 μGal/month with an uncertainty of ±0.03%. Given that the two gravimeters are only 13 m apart, long-term gravity differences due to surface deformation, atmospheric pressure variations, groundwater flow, and sea level changes are assumed to be negligible. Thus, the estimated linear component is likely attributable to the difference in instrumental drift between the gravimeters. This finding is consistent with the nominal accuracy of superconducting gravimeters, i.e., within 0.5 μGal/month. The high precision of the regression suggests that the six-year baseline measurement offers exceptional sensitivity for detecting gravity difference signals. Future research will focus on assessing potential gravity anomalies associated with CO2 geological storage.