Search

Abstract: On 15 August 2007, Pisco earthquake (magnitude 8.0) hit the central coast of Peru near the MAGDAS Ancon (ANC) station. Geomagnetic data from ANC and other reference stations have been analyzed to detect any signature related to this great earthquake. Results indicate the presence of annual geomagnetic variations in the vertical component at ANC and Huancayo (HUA) stations (in the vicinity of the epicenter of Pisco earthquake). These variations have a quasi-sinusoidal waveform with amplitudes of about 10 and 5nT for ANC and HUA stations respectively. They appeared clearly during the period preceding the onset of the Pisco earthquake especially at ANC station. By using HUA, Eusebio (EUS) and Kourou (KOU) as reference stations in the vicinity and away from the epicenter of Pisco earthquake, a clear disappearance of the diurnal variation of the vertical component was observed at ANC station during the day of earthquake. Moreover, the Pisco earthquake and another earthquake (on 29 March 2008) near ANC station were found to occur concurrently with the depressions in the polarization ratio (Z/H) of Pc 3 (10–45s) amplitude. Such anomalous variations appear to be a result of changes in the crustal stress field and the lithospheric conductivity in the studied region. [Copyright &y& Elsevier]

Abstract: The Molise region, on 31 October and 1 November 2002, was struck by two earthquakes of moderate magnitudes (Mw=5.7) at depth between 12 and 24km. Geomagnetic data from the Circum-pan Pacific Magnetometer Network (CPMN) were analyzed in order to detect any anomalous geomagnetic variations in association with the Molise earthquakes. Our results indicate the presence of long-term anomalous variations in the geomagnetic components at L’Aquila (LAQ) station (near the epicenter), which started about four months before the occurrence of the Molise earthquakes. Moreover, the geomagnetic components recorded at LAQ are found to show no correlation with those at other conjugate stations in the period between June and October 2002. In addition, anomalous ULF signal (Pc 3:10–45s) started few weeks before the Molise earthquakes and lasted for about one week after the onset of the seismic activity. The observed anomalous variations may be explained as a result of the crustal stress variations and the enhancement of the lithospheric conductivity in the Molise region during the preparation period of the Molise earthquakes. [Copyright &y& Elsevier]