Method and system for electroseismic monitoring of microseismicity

A method of determining the time of occurrence of a microseismic event and triggering a seismic recording device comprising the steps of:

• measuring electromagnetic energy using an electromagnetic sensor, at least some of the electromagnetic energy being caused by a microseismic event that consists primarily of rock fracturing or activation of existing rock fractures;
• estimating the time at which the microseismic event occurred based on the time at which electromagnetic energy caused by the microseismic event is received by the electromagnetic sensor;
• and
• initiating recording on a seismic recording device of seismic energy monitored by a ground motion sensor, the recording being initiated in response to the estimated time at which the microseismic event occurred.

A computer readable medium that carries instructions to direct an apparatus to determine the location of a microseismic event by performing steps comprising:

• receiving electromagnetic data representing electromagnetic energy traveling through the earth that has been measured by an electromagnetic sensor, at least some of the electromagnetic energy being caused by a microseismic event that consists primarily of rock fracturing or activation of existing rock fractures;
• receiving seismic data representing vibrations in the earth caused by said microseismic event, the seismic data being measured using plurality of ground motion sensors;
• estimating the time at which said microseismic event occurred based at least in part on the time at which electromagnetic energy caused by the microseismic event is received by the electromagnetic sensor;
• and
• determining the location of said microseismic event using the estimated time at which the microseismic event occurred and the time at which the earth vibrations caused by the microseismic event arrived at the ground motion sensors.

A system for determining the location of a microseismic event comprising:

• a plurality of ground motion sensors adapted to detect vibrations in the earth caused by a microseismic event that consists primarily of rock fracturing or activation of existing rock fractures;
• an electromagnetic sensor adapted to detect electromagnetic energy traveling through the earth caused by the microseismic event, the electromagnetic sensor generating data for an estimation of the time at which said microseismic event occurs based at least in part on the time at which electromagnetic energy caused by the microseismic event is received by the electromagnetic sensor;
• and
• a processor adapted to determine the location of said microseismic event using said estimation of time and the time at which the earth vibrations caused by the microseismic event arrived at said ground motion sensors,
• said ground motion sensors and said electromagnetic sensors being located within a borehole, a lateral extension of said borehole or at the ground surface.