Multi-Parameter Geophysical Observatory: gateway to integrated earthquake precursory research

摘要

To study earthquake precursors in an integrated manners India's first Multi-Parameter Geophysical Observatory (MPGO) has been established at Ghuttu, Central Himalaya. The MPGO is located in a narrow belt of high seismicity where the colliding Indian Asian plates are lacked and are accumulating strains for future great earthquakes. The observatory is equipped with a superconducting gravimeter, overhauser and fluxgate magnetometers, ULF band search coil magnetometer, GPS, radon and water-level recorders. Supplemented by the dense network of broadband seismometers, the MPGO is designed to record precursory signals resulting from stress-induced changes in density, Magnetization, resistivity, seismic wave velocity, fracture propagation, crustal deformation, electromagnetic and radon gas emission as well as fluctuations in hydrological parameters. The immediate priority for the characterization of precursory signals is to develop techniques to estimate and eliminate the background variation caused by the hydrological, environmental and-solar terrestrial dynamics related changes. A careful scrutiny of the data associated with the Kharsali earthquake (M-L = 4.9) of 22 July 2007, revealed unambiguous. co-seismic gravity jump perhaps related to the change in volumetric strain. Similarly, radon fluxes show some definite trend that can be viewed as pre- and co-seismic changes related with the Kharsali earthquake. Sudden drop of geomagnetic field intensity and dynamic waveform, lasting from several days before to a week after the earthquake, appears to be a manifestation of the thermal agitation on the magnetization of rocks around the source region of the earth quake: A new method-of location of seismo-EM source has been developed and its efficacy), demonstrated in the seismically active Koyna region. The results obtained so far-show that the Multi-parameter approach crafted by the Ministry of Earth Sciences under the National Program on Earthquake Precursors holds promise and long-term monitoring needs to be continued for statistical validation.