Underground earth strain and seismic radiation measurements with a laser interferometer and a dense small-aperture seismic array

Abstract

This paper describes two geophysical instruments, installed in the underground physics laboratories of Gran Sasso (LNGS-INFN), located in the seismic zone of the Central Apennines, Italy. These instruments monitor strain and seismic radiation with very high sensitivity: one is a 90 m-long laser interferometer, sensitivity 3 x 10-12, frequency response 10-7-10-2 Hz, and has been operating since 1994. The other is a small-aperture seismic array composed of 21 three-component short period (Mark L4C-3D) and 3 broadband (Guralp CMG-3ESP) seismometers. This dense array will be in operation at the beginning of 1998.

Keywords

• strain
• seismic array
• seismometry