• V I Keilis-Borok

      Articles written in Journal of Earth System Science

    • On intermediate-term prediction of strong earthquakes in the Himalayan arc region using pattern recognition algorithm M8

      S C Bhatia S V Chalam V K Gaur V I Keilis-Borok V G Kosobokov

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      Seismicity of the Himalayan arc lying within the limits shown in figure 1 and covering the period 1964 to 1987 was scanned using M8 algorithm with a view to identifying the times of increased probabilities (TIPs) of the occurrence of earthquakes of magnitude greater than or equal to 7·0, during the period 1970 to 1987. In this period, TIPs occupy 18% of the space time considered. One of these precedes the only earthquake in this magnitude range which occurred during the period. Two numerical parameters used in the algorithm, namely the magnitude thresholds, had to be altered for the present study owing to incomplete data. Further monitoring of TIPs is however warranted, both for testing the predictive capability of this algorithm in the Himalayan region and for creating a base for the search of short-term precursors.

    • Application of pattern recognition algorithm in the seismic belts of Indian convergent plate margin — CN algorithm

      V K Gagakayt I V Kuznetsov I M Rotwain A M Gabruekiv V I Keilis-Borok

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      The earthquake catalogue from 1964 to August 1991 is used to identify the times of increased probabilities (TIPs) of the earthquake mainshocks of magnitudes greater than or equal to 6·4 and are associated with the Indian convergent plate margins, in retrospect. In Pakistan and Indo-Burma regions, the analysis was repeated for magnitude threshold 6·2 and 7·0 respectively. All the earthquakes (except one in the Hindukush region and one in Indo-Burmese region) in Pakistan, Hindukush-Pamir, Himalaya and Indo-Burmese regions were preceded by the special activation and hence were predicted.

      Approximately 23 ± 10% of the total time (1970 to August 1991) is occupied by the TIPs in all the regions. The reasons for failure to predict the two earthquakes in these regions are discussed.

      Our analysis gives a better picture of the regionalization and the size of the space-time volume for the preparation of an earthquake. The high success ratio of the algorithm proves that it can be applied in this territory for further prediction in the real time, without any significant changes in its parameters.

    • Application of pattern recognition algorithm in the seismic belts of Indian convergent plate margins — M8 algorithm

      V K Gahalaut I V Kuznetsov V G Kosobokov A M Gabrielov V I Keilis-Borok

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      The seismicity associated with the convergence of the Indian and Eurasian plates, from 1964 to August 1990 was scanned using the M8 algorithm with a view to identify the times of increased probabilities (TIPs) of the earthquakes of magnitudes greater or equal to 6·4 that occurred during the period from 1970 to August 1990. 23 out of 28 earthquakes (M ⩾ 6·4) have been predicted. These were preceded by specific activation of the earthquake flow which was picked up by the M8 algorithm. The earthquake of August 1988 in the Himalaya could not be predicted, the other four unpredictable earthquakes occurred in the early dates of the catalogue (1970–1971) and hence their TIPs could not be diagnosed. Two current alarms are diagnosed, one in the Indo-Burmese arc and the other in the Hindukush-Pamir region.

      The algorithm provides the correlation between the earthquakes and their area of activation (both in time as well as in space) which, when compared with the local geology, may help to comment on the present day status of the seismic features on the surface.

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