Recent Earthquakes in Arunachal Himalaya

Of late, there has been a rise in the number of earthquakes in the North East Region (NER) of India. Very recently, a mild tremor shook the East Kameng district of Arunachal Himalaya, when a shallow-depth (16.8 km) earthquake of M_W 5.5 with epicentre 27.707°N and 92.890°E struck at UTC 09 h 22 m 15 s (14 h 52 m 14 s ITC) on 19 July 2019 (refs 1, 2). Importantly, within half an hour two aftershocks were recorded, one in the same epicentral zone of the M_W 5.5 earthquake and another at the southern site of East Kameng district² (Table 1). A M_W 4.9 earthquake was recorded at UTC 22 h 54 m 24 s (04 h 24 m 23 s ITC on 20 July 2019) with epicentre 27.736°N and 92.810°E and depth of 10 km. The highest impact of these earthquakes was felt in the epicentral zone of East Kameng district and in the adjoining regions of Arunachal Pradesh, Guwahati and other parts of Assam and Dimapur, Nagaland. The NER is one of the highly seismically active regions^3,4 and falls in the zone V in the seismic zoning map of India (BIS 2004)⁵. In this context, these felt events are significant because of their epicentral region being located in the NER itself. Figure 1 shows the epicentral plot of the earthquakes and focal mechanism of two earthquakes (from USGS) with prominent tectonic elements of NE India.