Difficulties with interpreting changes in groundwater gas content as earthquake precursors in Kamchatka, Russia |
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| Authors: | PF Biagi A Ermini SP Kingsley YM Khatkevich EI Gordeev |
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| Institution: | (1) Department of Physics, University of Bari, Via Amendola, 173-70126 Bari, Italy;(2) Department of Physics and Energy Science and Technology, University of Roma `Tor Vergata', Via di Tor Vergata –, 00133 Rome, Italy;(3) Sheffield Centre for Earth Observation Science, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, U.K.;(4) Experimental and Methodical Seismological Department, Geophysical Service Russian Academy of Science, Pijp Av. 9, Petropavlovsk-Kamchatsky, 683006, Russia |
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| Abstract: | The Kamchatka peninsula, located in the far east of Russia, is a geologicallyactive margin where the Pacific plate subducts beneath the North Americanand Eurasia plates. This area is characterised by frequent and strong seismicactivity (with magnitudes of up to 8.6), with epicentres generallydistributed offshore along the eastern coast of the peninsula. Starting in1977, hydrogeochemical data have been collected with a mean samplingfrequency of three days in wells and springs located in the southern area ofthe Kamchatka peninsula. In order to reveal possible earthquake precursors,the groundwater gas content data collected in the last ten years at fivewells, were statistically analysed. Each signal exceeding a 3 threshold was considered to be an irregularity and two different methodsof defining an anomaly were assumed. In the first, an anomaly was declaredwhen an irregularity occurred simultaneously on more than one gas contentat each well. In the second method, an anomaly was declared when anirregularity occurred simultaneously on a given type of gas at more thanone well. As a mechanism for associating an anomaly with an earthquake,the earthquakes that occurred with magnitudes greater than 6.5 and withina distance of 250 km from each well, were selected. Using this frameworkboth successes and failures were identified. It is shown that on the basis ofthis statistical analysis, there is a great probability that the successes revealedare not precursors but random coincidences. |
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| Keywords: | chance earthquakes gases groundwater Kamchatka precursors |
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