Geology. The deadliest intraplate earthquake

Uttarakhand State Earthquake Early Warning System: A Case Study of the Himalayan Environment

The increased seismic activity observed in the Himalayas, coupled with the expanding urbanization of the surrounding areas in northern India, poses significant risks to both human lives and property. Developing an earthquake early warning system in the region could help in alleviating these risks, especially benefiting cities and towns in mountainous and foothill regions close to potential earthquake epicenters. To address this concern, the government and the science and engineering community collaborated to establish the Uttarakhand State Earthquake Early Warning System (UEEWS). The government of Uttarakhand successfully launched this full-fledged operational system to the public on 4 August 2021. The UEEWS includes an array of 170 accelerometers installed in the seismogenic areas of the Uttarakhand. Ground motion data from these sensors are transmitted to the central server through the dedicated private telecommunication network 24 hours a day, seven days a week. This system is designed to issue warnings for moderate to high-magnitude earthquakes via a mobile app freely available for smartphone users and by blowing sirens units installed in the buildings earmarked by the government. The UEEWS has successfully issued alerts for light earthquakes that have occurred in the instrumented region and warnings for moderate earthquakes that have triggered in the vicinity of the instrumented area. This paper provides an overview of the design of the UEEWS, details of instrumentation, adaptation of attributes and their relation to earthquake parameters, operational flow of the system, and information about dissemination of warnings to the public.

Dynamic Relationship Study between the Observed Seismicity and Spatiotemporal Pattern of Lineament Changes in Palghar, North Maharashtra (India)

The Palghar region (north Maharashtra, India), located in the northwestern part of the stable continental region of India, experienced a low magnitude earthquake swarm, which was initiated in September 2018 and is continuing to date (as of October 2021). From December 2018 to December 2020, ~5000 earthquakes with magnitudes from M1.2 to M3.8 occurred in a small region of 20 × 10 km2. These earthquakes were probably triggered by fluid migration during seasonal rainfall. In this study, we have used multi-temporal Landsat satellite data of the year 2000, 2015, 2018, 2019, and 2020, extracted lineaments, and studied the changes in frequency and pattern of lineaments before and after the initiation of the swarm in the Palghar region. An increase in the lineament density and amount of rainfall are found to be associated with the increasing frequency of earthquakes.

The New Madrid Seismic Zone: not dead yet

The extent to which ongoing seismicity in intraplate regions represents long-lived aftershock activity is unclear. We examined historical and instrumental seismicity in the New Madrid central U.S. region to determine whether present-day seismicity is composed predominantly of aftershocks of the 1811-1812 earthquake sequence. High aftershock productivity is required both to match the observation of multiple mainshocks and to explain the modern level of activity as aftershocks; synthetic sequences consistent with these observations substantially overpredict the number of events of magnitude ≥ 6 that were observed in the past 200 years. Our results imply that ongoing background seismicity in the New Madrid region is driven by ongoing strain accrual processes and that, despite low deformation rates, seismic activity in the zone is not decaying with time.