On the possibility of determining the focal parameters of an earthquake using a local network equipped with three-component seismometers

Abstract

Bv exploiting the possibility of determining the angle of emergence<br />and the azimuth of a seismic ray at an observation point equipped with<br />one vertical seismograph and two horizontal ones and using recent digital<br />data acquisition techniques, an effective method for locating the focus<br />of a seismic event is proposed. By means of this method it is possible<br />to obtain, in addition to the point customarily considered as the "barycentre"<br />of the focal volume, also a quantity which represents the "convergence"<br />of various seismic rays on the source zone.<br />This method makes it possible actually to "determine" the focal parameters<br />and does away with the need for approximation methods of the<br />least squares type.<br />In the present investigation, tests have been carried out to determine<br />the accuracy of the angle of emergence and the azimuth for a number<br />of earthquakes, together with other theoretical tests for the relocation ot<br />the focal parameters using a three-dimensional crust model.