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pure and applied geophysics

, Volume 157, Issue 9, pp 1359–1377 | Cite as

Groundwater Ion Content Precursors of Strong Earthquakes in Kamchatka (Russia)

  • P. F. Biagi
  • A. Ermini
  • S. P. Kingsley
  • Y. M. Khatkevich
  • E. I. Gordeev

Abstract

—The Kamchatka peninsula, located in the far east of Russia, is a geologically active margin where the Pacific plate subducts beneath the North American and Eurasia plates. This area is characterised by frequent and strong seismic activity (magnitudes reaching 8.6) and epicentres are generally distributed offshore along the eastern coast of the peninsula. For many years, hydrogeochemicals have been sampled with a mean interval of three days to measure the most common ions in the groundwater of five deep wells in the southern area of the Kamchatka peninsula. In the last decade, five earthquakes with M > 6.5 have occurred at distances less than 250 km from these wells. These earthquakes were powerful enough for them to be considered as potential originators of precursors. In order to reveal possible precursors of these earthquakes, we analysed the groundwater ion contents. The quasi-periodic annual variation was filtered out, together with other slow trends, and then we smoothed out the high frequency fluctuations that arise from errors in a single measurement. When examining the data, we labelled each signal with an amplitude greater than three times the standard deviation as an irregularity and we made a first attempt at defining an anomaly as an irregularity occurring simultaneously in more than one parameter at each well. In a second definition we used the existence of an irregularity occurring simultaneously in each ion at more than one well. Then, on the basis of past results worldwide and the time interval between the earthquakes observed, we chose 158 days as the maximum temporal window between a possible anomaly and the subsequent earthquake. With the first anomaly definition we identified 6 anomalies with 4 possible successes and 2 failures. For the five earthquakes considered capable of producing precursors we obtained precursors in three cases. With the second anomaly definition we identified 10 anomalies with 7 possible successes and 3 failures and we obtained precursors in four of the five earthquakes. A schematic model explaining aspects of the complex relationship linking earthquakes and ion content anomalies is also presented.

Key Words: Precursors, earthquakes, groundwater, ions, Kamchatka. 

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Copyright information

© Birkhäuser Verlag Basel, 2000

Authors and Affiliations

  • P. F. Biagi
    • 1
  • A. Ermini
    • 2
  • S. P. Kingsley
    • 3
  • Y. M. Khatkevich
    • 4
  • E. I. Gordeev
    • 4
  1. 1.Department of Physics, University of Bari, via Amendola 173, 70126 Bari, Italy. E-mail: Biagi@fisica.uniba.itIT
  2. 2.Department of Physics and Energy Science and Technology, University of Roma, Tor Vergata, Via di Tor Vergata, 00133 Rome, Italy.IT
  3. 3.Sheffield Centre for Earth Observation Science, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom.GB
  4. 4.Experimental and Methodical Seismological Department, Geophysical Service Russian Academy of Science, Pijp Av. 9, Petropavlovsk-Kamchatsky 683006, Russia.RU

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