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Evaluation of parameters controlling Earthquake Management System : An analytical approach using 3S' Technology

Frequency of Foreshock
There are cases where minor foreshocks have indicated the major coming shock. So it is highly desirable to establish the seismological observatory for the continuous monitoring of seismic activity in an area. In modern time, earthquakes are studied with more authenticity, as high quality seismic and geodetic data are available globally. India has also made substantial progress in this field with the establishment of Broad band digital seismograph and geodetic network. Data accumulated through the seismological, geological and geodetic observations can be of great help in the delineation of the earthquakes prone areas. This will have direct impact on the hazard assessment and public safety measures.

For this purpose in India a network of observations have been set up by Indian meteorological department, which include 45 national observatories and 13 special purpose observatories. The seismological laboratories help us in demarcating an area with varying seismicity. On that basis India has been divided into 5 zones with respect to intensity of earthquake. Of these, zone v is seismically the most active where earthquake of magnitude 8 or more could occur. Zone I is the least active region.

There are various parameters, which can be analyzed collectively for the purpose of an earthquake prediction. Surface parameter include topographical changes and subsurface parameter include subsurface geomagnetic, geothermal and gravity variation. Rates of uplift and subsidence, specially rapid or anomalous change may be significant in predicting earthquake. For example for more than ten years before the 1964 earthquake near Nigata, Japan there was anomalous uplift of the earth crust. It has also been observed that speed of primary waves may decrease for a month, and then increase to normal just before an earthquake. With recent advancement in science & technology, a proper sensor developed to measure these variations can be put on satellite to get regional idea by periodic and continuous monitoring of these variations and their quantification may helps us in forecasting of such hazardous events. Changes in the electrical resistivity of an area have also been reported before earthquake. Increase in the amount of radioactive radon gas that is dissolved in deep well water has also been reported.

b) Earthquake preventive measures
The main objective of earthquake preventive measures should be to develop and promote knowledge, practices and policies that reduce fatalities, injuries and other economic losses from earthquake. Providing Geoscientific information to the masses can well minimize these losses. Formulation of preventive measures includes:

1. Compiling digital surfacial geological maps to find out area more prone to crustal movement.
2. Preparation of ground shaking amplification maps to demarcate area susceptible to high amount of destruction.
3. Preparation of liquefaction and lateral spreading susceptibility maps
4. Preparation of landslide susceptibility maps mainly in high relief region to delineate area highly susceptible to landslide
5. Compilation of GIS databases of existing data on active earthquake source zones and make these databases easily accessible to user groups
6. Modification of palaeoseismological maps
7. Geoscientific modeling of the shallow crust using seismic, geodetic and geological data for earthquake hazard evaluation.

Earthquake hazard prevention depends on proper understanding of the destructive effect of earthquake. The areas of interest in earthquake studies include the effect of the earthquake source, local and regional geological structure and near surface geological deposits on strong ground shaping. Seismic and crustal deformation monitoring network can provide real time information for emergency response. GIS database of active earthquake source zone with up to date information on slip-rate and recurrence intervals will improve earthquake hazard identification and risk assessment.

Conclusion :
A variety of methods have been used for earthquake prediction, ranging from planetary movement to odd behavior of animal but earthquake prediction continue to be an elusive goal. There have been isolated cases of success, most of which are of long range and intermediate range prediction based on seismic zone delineation. Short- term earthquake prediction is still the biggest scientific challenge today. In the absence of a reliable tool for short- term prediction the only thing we are able to do is to get prepared for post-earthquake rehabilitation measure and adopt an action plan with the objective of

1. The improvement in the understanding of earthquake occurrence, their effect and consequence.
2. Improvement in the area of earthquake hazards identification and risk assessment method and their use.
3. Maintenance and improvement of comprehensive earthquake monitoring with focus on real time system in urban areas.