http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/596 2026-04-29T10:23:40Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1024 Title: The 2020 Mw 5.5 Mizoram earthquake and associated swarm activity in the junction of the Surma Basin and Indo‑Myanmar Subduction Region Authors: Bharali, Bubul Abstract: A severely felt earthquake of Mw 5.5 occurred on 22 June 2020, in the Champhai district of Mizoram, North East Region (NER) of India, in the vicinity of the Indo-Myanmar subduction zone. This earthquake was associated with a swarm type of activity; six earthquakes of Mw 4.0–5.1 and some 16 earthquakes of Mw 3.0–3.9 occurred almost within two months like a swarm which caused much panic in the Mizoram state and neighbouring region. The mainshock of Mw 5.5 was preceded by an earthquake of Mw 5.1 on the previous day, 21 June 2020, in the capital city Aizawl,~70 km northwest of Champhai. All of these events originated at shallow depth (~10–30 km) and occurred in the intra-plate zone of the subducting Indian plate. Fault plane solution of the mainshock indicates strike-slip faulting that matches fairly well with the transverse Mat Fault in the Outer Indo-Burma Wedge (OIBW). Macroseismic investigation of the mainshock at some 46 sites shows the maximum intensity of VIII (MMI scale) at the epicentral track. An attenuation relation between intensity and hypocentral distance is derived, which may be helpful to assess seismic hazards in this region. 2021-07-04T00:00:00Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/598 Title: Sedimentological Characteristics of the Barail Arenaceous Unit of Makum-North Hapjan Oil Field, Assam Authors: Bharali, Bulbul Abstract: Upper Assam Shelf is one of the major on-shore hydrocarbon producing basin in India. It comprises sediments of upper Paleocene to recent and rest unconformably over the Granitic Basement. The Barail Group (Oligocene) of rocks in this basin is characterized by hydrocarbon source rock as well as reservoir rock. The Barail Group of rocks is divided into Arenaceous Unit (lower) and Argillaceous Unit (upper) in Upper Assam basin. The Arenaceous Unit is considered as good reservoir rock, where as the upper Argillaceous Unit is considered as source rock. The aim of the present research work is to characterize the Barail Arenaceous Unit of Makum-North Hapjan oil field with respect to its mineralogical constituents and textural properties. The present study reveals that the Barail reservoir sandstones in Makum- North Hapjan oil field are sublithic-arenite varieties with moderately well sorted texture and deposited in a fluvio-deltaic environment under the intermittent influence of transgressive and regressive effects. The sediments were derived from multiple provenances primarily comprising of reworked sediments and low rank metamorphic rocks. 2019-04-15T00:00:00Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/597 Title: A geological study on Upper Bhuban Formation in parts of Surma Basin, Aizawl, Mizoram Authors: Bharali, Bulbul Abstract: Tertiary sediments are thickly deposited in most part of the northeast India attaining a maximum thickness of ±7 km sedimentary succession. Surma basin located in the eastern proximity of India is also characterized by a thick sedimentary column which can be considered as the northeastern extension of Greater Bengal basin. This basin was initiated due to the mutual collision between Indian and Burmese Plate. Due to this collision, the bed rocks have undergone folding which are oriented N-S trending hill ranges. The basin was also cut by a number of parallel to sub-parallel transverse faults and thrusts. The litho association is consisting of sandstone, siltstone, shale and their various proportions. The present study focused on the provenance of the sediments, tectonic settings of the basin and various paleoclimatic conditions prevailing during the time of deposition by using petrography, granulometric and heavy mineral analysis of representative rock samples which were collected from various parts of Aizawl district of Mizoram belonging to the Upper Bhuban Formation. Based on the various proxies it was confirmed that the sediments were primarily derived from surrounding orogens and deposited in a shallow marine basin under the influence of fluvial-deltaic conditions which were basically sourced from felsic provenance. The sediments were moderately weathered under semi-humid to humid climatic condition before they deposited into Surma basin. Sandstones samples are litharenite and wacke type which were deposited in an active continental margin to recycled orogen settings. 2017-09-04T00:00:00Z