Geomagnetic Field Behaviour at Muntele Rosu (Romania) and Anomaly Interpretation

World Multidisciplinary Earth Sciences Symposium

Andrei, Mihai^1 ; Iren-Adelina, Moldovan^1 ; Victorin, Toader^1 ; Laura, Petrescu^1 ; Raluca, Partheniu^1

National Institute for Earth Physics, RO-077825, Calugareni st, no 12, Magurele, Ilfov, Romania^1

关键词: Data acquisition system;    Earthquake magnitudes;    Geomagnetic indices;    Geomagnetic measurement;    Intermediate depths;    Intermediate-depth earthquakes;    Meteorological phenomena;    Temperature variation;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/221/1/012055/pdf
DOI  :  10.1088/1755-1315/221/1/012055

来源: IOP

【 摘 要 】

In this study were used geomagnetic data recorded during last 5 years, from 2013 till present. The records were corrected for missing and wrong data induced by malfunction of the data acquisition system. The main purpose of the paper is to identify the magnetic field behaviour in relation with space weather, meteorological phenomenon including annual/diurnal temperature variation, local and regional seismic activity. The paper is focusing on geomagnetic anomalies detected on the recorded field at one magnetometer located near Vrancea seismogenic zone prior to Mw>4.5 crustal and intermediate depth earthquakes. During these 5 years of investigations one crustal earthquake and three subcrustal earthquakes with a moment magnitude Mw between 5.0 and 6.0, occurred in the Vrancea zone. All three intermediate depth events were accompanied by significant anomalies on Y axis (EW component) of local geomagnetic field measured at MLR observatory. The MLR magnetometer was outside the preparation zone of the crustal earthquake, located at 100km distance from the epicenter, so no anomaly was observed. In order to highlight the anomalies recorded at Muntele Rosu (MLR) seismological observatory, these data were compared with data from Surlari (SUA) observatory, located about 150 Km South-East outside the Vrancea seismogenic zone. Similarly, earthquakes with Mw between 4.5 and 5 are accompanied by same type but smaller amplitude anomalies, were the drop on Y axis was less than 10 nT instead of 20-30 nT as those occurred prior to earthquakes with Mw>5.0. The latter ones are harder to observe during the summer time when these anomalies are hidden by large diurnal variations. The anomaly duration extends from days to sometimes months, without correlation with the earthquake magnitude. To better distinguish the local/regional anomalies from global geomagnetic behaviour, both MLR and SUA datasets were also corelated with the geomagnetic indices from NOAA/Space Prediction Center. The presence of geomagnetic storms creates a specific type of anomalies that sometimes might hide the ones related to earthquakes. The geomagnetic measurements were also compared with temperature values recorded at MLR station both for avoiding wrong interpretation of instrument response related to temperature variations, and to highlight possible correlations of magnetic field behaviour with ambient temperature. The three medium sized intermediate earthquakes that have occurred in the studied time interval provided a good opportunity to investigate the link between the presence of anomalies on geomagnetic records at Muntele Rosu observatory and seismicity in Vrancea zone.