Abstract: An apparatus for estimating the origin time, the hypocentral distance, and the scale from time-series measured data of the electric field intensity which is observed accompanying a seismic ground motion, comprising a measuring means 21, 22 for measuring the electric field intensity, a data storing means 24, 25 for collecting and storing measured data from the measuring means, and a data analyzing means 26 for analyzing measured data stored in the storing means to detect origin time from the starting time of electric field increase, and to predict the hypocentral distance and the magnitude from the elapsed time from said origin time and said measured data, is provided.

Abstract: An apparatus for estimating the origin time, the hypocentral distance, and the scale from time-series measured data of the electric field intensity which is observed accompanying a seismic ground motion, comprising a measuring means 21, 22 for measuring the electric field intensity, a data storing means 24, 25 for collecting and storing measured data from the measuring means, and a data analyzing means 26 for analyzing measured data stored in the storing means to detect origin time from the starting time of electric field increase, and to predict the hypocentral distance and the magnitude from the elapsed time from said origin time and said measured data, is provided.

Abstract: A casing pipe is inserted into a drilled hole reaching the inside of a confined aquifer in which groundwater is stored and flows or a position near the confined aquifer. A measuring device measures an electromagnetic field at the distal end of the casing pipe. An analyzing device analyzes data concerning the electromagnetic field measured by the measuring device to sense motion of ground pore water, thereby predicting rapid motion in the earth's crust, such as a volcanic eruption, an earthquake, a landslide and ground collapse. The casing pipe is an electrically conductive pipe having a non-magnetic screen portion formed at the distal end thereof so that recycling groundwater passes through the screen portion. The measuring device includes an electromagnetic field sensor placed in the screen portion and the conductive casing pipe as an electrode for measuring an electric potential relative to an electric potential at the earth's surface detected with a reference electrode.

Abstract: A seismic electromagnetic field signal is detected at each of observation stations installed at at least two places, and civil noise and atmospheric discharge noise are eliminated from the signal to obtain a low-frequency seismic electromagnetic field signal O.sub.s. A local characteristic signal C.sub.e and a refined local characteristic signal C.sub.f are obtained by processing the signal O.sub.s. The signals O.sub.s, C.sub.e and C.sub.f are transmitted to a central station. At the central station, a delay time T and a half-width H are obtained from the cross-correlation function between the observation stations, and further a regional characteristic signal C.sub.r is obtained from the seismic electromagnetic field signal O.sub.s. An earthquake source region distribution, an earthquake magnitude, and earthquake occurrence time are estimated on the basis of the signals obtained at the central station and the local characteristic signal C.sub.e and refined local characteristic signal C.sub.

Abstract: The source region of a volcanic tremor is determined by simultaneously detecting the tremor using seismometers installed at at least four separate points, obtaining correlation functions among pairs of the detected values, calculating at least three observation time lags corresponding to the maximal values of the correlation functions, and using the at least three observation time lags for determining the source region of the volcanic tremor.

Abstract: The probability of a volcanic eruption is predicted by simultaneously receiving long-wave radiation signals from magma at at least four points in the vicinity of the magma, cross-correlating the received signals to detect time lags among the signals, calculating the site, magnitude and shape of the magma from the time lags, and judging the likelihood, time, scale and site of a volcanic eruption from time-course changes in the calculated site, magnitude and shape of the magma.