Several clusters of unusual natural incidents have been observed throughout the Kerala State, Southwestern parts of India during the periods: February to March, 2001 (phase I), and June to November, 2001 (phase II). The incidences like fluctuations and rise in water levels, wavy formations and spouting of water in the open wells, cracks in the buildings, perceptible fissures in the ground, shaking of trees/bushes and enhanced minor earthquakes activity have been observed during Phase I; whereas the collapse of shallow open wells, draining of water, lowering of water level, land subsidence, ground fissures and further increased minor earthquake activities, etc., were the dominating incidents during Phase II.
The frequency of occurrences of these incidents was drastically reduced after November 2001 though. There are events of a few minor earthquakes which occurred during 2002-2006. The temporal patterns of occurrences of such incidences during Phase I and Phase II might have been the outcome of periodic stress release in the region. In the present paper, the study on the occurrence of the chain of events coupled with the existence of anomalous seismic activity has been done in the light of the dilatancy diffusion model and the results signify that the region is preparing for a major earthquake in future.
The events such as the land deformation, changes in some of the parameters sea level, tilt, strain and crustal stress, foreshocks, anomalous seismic activity, b-value, and also changes in seismic wave velocity, underground water levels, radon content, water and gas spouting etc., are known to precede medium to large earthquakes (Sekiya, 1976; Wakita, 1978; Zhu and Zhong, 1979; Rikitake, 1982; Wang Chen-min et al., 1984; Sadovsky et al., 1984; Singh et al., 2005a). It is well known that there is a one-to-one correlation between the premonitory events and the main earthquakes (Rikitake, 1982; Scholz, 2004). |
