A high sensitivity very low frequency (VLF) receiver is developed based on AD744 monolithic operational amplifier (Op-Amp) for earthquake data acquisition. In research related natural phenomena such as atmospheric noise, lightning and... more
A high sensitivity very low frequency (VLF) receiver is developed based on AD744 monolithic operational amplifier (Op-Amp) for earthquake data acquisition. In research related natural phenomena such as atmospheric noise, lightning and earthquake, a VLF receiver particularly with high sensitivity is utterly required due to the low power of VLF wave signals received by the antenna. The developed receiver is intended to have high sensitivity reception for the signals in frequency range of 10-30kHz allocated for earthquake observation. The VLF receiver which is portably designed is also equipped with an output port connectable to the soundcard of personal computer for further data acquisition. After obtaining the optimum design, the hardware realization is implemented on a printed circuit board (PCB) for experimental characterization. It shows that the sensitivity of realized VLF receiver is almost linear in the predefined frequency range for the input signals lower than-12dBm and to be quadratic for the higher level input signals.
Himalayan region is one of the most seismically active regions of the world. Shillong plateau in North East India has been identified as one of the six most tectonically active regions of the world. Only limited strong motion records are... more
Himalayan region is one of the most seismically active regions of the world. Shillong plateau in North East India has been identified as one of the six most tectonically active regions of the world. Only limited strong motion records are available for earthquakes in India. India has a number of network consisting strong motion accelerographs in the high seismic zone, but these cannot be termed as sufficient. In addition, about 350 structural response recorders (SRR) has been installed in different parts of the country in the recent past.
The scope of this paper is to analyse the data recorded by SRR instrument with specific objectives of: (a) assessing the degree of uniformity between the SRR data, (b) examining the
similarity between information from SMA and SRR data, and (c) developing a methodology for the computation of peak ground acceleration (PGA) from SRR data.
Three complete data sets of strong earthquakes (M-> 5.5), which occurred in the seismic regions of Chile, Mexico and Kamchatka during the time period 1899-1985, have been used to test the existence of a time-lag in the seismic energy... more
Three complete data sets of strong earthquakes (M-> 5.5), which occurred in the seismic regions of Chile, Mexico and Kamchatka during the time period 1899-1985, have been used to test the existence of a time-lag in the seismic energy release between these regions. These data sets were cross-correlated in order to determine whether any pair of the sets are correlated. For this purpose statistical tests, such as the T-test, the Fisher's transformation and probability distribution have been applied to determine the significance of the obtained correlation coefficients. The results show that the time-lag between Chile and Kamchatka is-2, which means that Kamchatka precedes Chile by 2 years, with a correlation coefficient significant at 99.80% level, a weak correlation between Kamchatka-Mexico and noncorrelation for Mexico-Chile.
