Figure 15. Regional network of 11 broadband seismological stations in NE India operated by Indian Institute of Geomagnetism. (Courtesy IIG)
    A regional network of 11 broadband seismological stations has been established and operated by IIG in NE India (Fig.15) to study the geometry and continuity of crust and upper mantle discontinuities beneath the region, seismic ambient noise tomography focusing primarily on crustal and uppermost mantle structures, and crustal attenuation characteristics of high frequency body waves.
    Strong motion accelerographs (SMA) have been installed and operated by CSIR-NEIST at different places in and around the Shillong Plateau and Mikir Hills. The acceleration time histories obtained from these accelerographs are filtered and processed for baseline corrections on a regular basis. These are then used as inputs for the estimation of several ground motion parameters including PGA, PGV and PGD, and Response spectra. A total of 234 earthquake events (M \(\ge\) 3.5) have been recorded by these SMA stations during Sep.2016 to Sep.2021.
    The Gujarat State Seismic Network (GSNet) under the aegis of the ISR, Gandhinagar, is operational since July 2006 (Fig.16). Presently, the network consists of 54 broadband seismograph stations (BBS) spread out in the state and neighboring areas. The data from almost 45 BBS are transmitted to the Institute through VSAT, where the earthquake activity is monitored in near real time (24x7).The network has a detectability of M 1.5 in the Kachchh region and M 2.0 in the other areas of Gujarat. Based on earthquake data of the Gujarat region, ISR developed a calibrated local magnitude scale (ML) for Kachchh and Saurashtra regions. ISR has also procured 10 compact broadband sensors with 4G connectivity. In addition, 54 strong motion accelerographs are also deployed by ISR. It has also established three MPGOs in Kachchh for earthquake precursory studies.