First observation of S-2(1) and study of the splitting of the football mode S-0(2) after the June 2001 Peru earthquake of magnitude 8.4 - art. no. 2111

摘要

1] The recent Peru earthquake with a moment magnitude M-w = 8.4 on June 23, 2001 presents a good opportunity for the observation of the seismic gravest normal modes. For the longest periods, below 1 mHz Superconducting Gravimeters (SGs) have been shown to be less noisy than long-period seismometers. A stack based on the spatial and temporal properties of the modes of degree one in a spherical harmonic development applied to 164 h of common records at the Cantley, Canberra, Strasbourg, Sutherland and Vienna SG stations has led to the first clear observation of the S-2(1) long-period seismic modes with a central frequency close to 0.4 mHz. Moreover the spectrum of the SG record at the Strasbourg station confirms the benefit SGs can provide to normal mode seismology with the clear observation of the splitting of the fundamental mode S-0(2) into 5 fairly well resolved singlets with only one record. [References: 25