Anomalous strain response to rainfall in relation to earthquake occurrence in the Tokai area, Japan.

Abstract

The effect of rainfall on crustal strain at the Mikawa Crustal Movement Observatory, central Japan, was studied in detail with a data set from January 1974 through December 1984. Changes in crustal strain caused by rainfall were successfully simulated by a tank model, in which the crustal strain is given as a nonlinear function of precipitation and time. The simulation error was usually less than 10%, but occasionally it became larger. There were anomalies of two kinds: 1) a change in spatial distribution of strains in the observation tunnel; and 2) an increase in simulation error for the rainfall effect. These anomalous responses seem to be related to the occurrence of nearby earthquakes within a particular area around the observatory. The logarithmic duration time of anomaly was roughly proportional to the earthquake magnitude. Data from the past eleven years indicate that about 50% of M @/*9/@ 3.5 earthquakes in the area were preceded by anomalous strain responses if they occurred after rain. The change in strain response to rainfall at this observatory could be a precursor of a nearby earthquake.

Monitoring deformation from hydrologic processes in a karst aquifer using long‐baseline tiltmeters

“…Since the pioneering work of Michelson [1914], interferometric instrument development has progressed to show a stability better than 10 −8 rad/month with low noise levels (better than 10 −10 rad) [ Boudin et al , 2008; d'Oreye and Zurn , 2005]. Tilt deformation of a hydrological nature has been considered noise for geophysicists [ Dal Moro and Zadro , 1998; Yamauchi , 1987; Zadro and Braitenberg , 1999]. However, tiltmeters have recently been set up for the specific study of hydrology.…”

Estimating the hydrologic induced signal in geodetic measurements with predictive filtering methods

“…Wolfe et al [ 1981 ] apply models of known hydrologic mechanisms, as infiltration and outflow of water from the ground, in order to find empirical models for the rain-strain relationship. Yamauchi [1987] uses an alternative method for simulating groundwater flow, which considers concatenated tanks fed in one another. The outflow from the last tank is used to simulate the strain variation.…”

Recent Results Obtained from Continuous Monitoring of Crustal Deformation.

“…In regard to short-term anomalous strain and tilt changes before the occurrence of earthquakes, several authors (e.g., Sato et al, 1984;Ohya, 1988) reported cases in which an anomalous change was detected by only one component of tiltmeters or extensometers at intermediate distances from epicenters (about 30-60km). Other reports (e.g., Tanaka, 1989;Yamauchi, 1987) have involved some uncertainties with respect to meteorological disturbances. As a result, we have not yet obtained reliable evidence of earthquake precursors which should be observed simultaneously with more than two instruments or at more than two observation sites after environmental and instrumental noise is carefully eliminated from the original data.…”

“…In such a shallow tunnel, apparent changes on tilt records can be caused by deviation of meteorological quantities from their mean annual curves. Yamauchi (1987) discussed precursory strain changes from another point of view, that is to say, "anomalous strain response to rainfall in relation to earthquake occurrence." In his study, the observed crustal strains were compared with estimated strains which were obtained using a "tank model."…”