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This study explores the seismotectonics of Kachchh in western India, a region with a low-to-moderate strain rate and a history of significant earthquakes, notably the 1819, Mw 7.8 Allah Bund, and the 2001, Mw 7.6 Bhuj. Despite its substantial seismic risk, comprehensive studies on Kachchh's seismogenic sources are scarce. This is attributed to the concealed nature of active structures, hindering definitive age constraints in paleoseismological research. Our research comprises a detailed paleoseismic analysis of the north-verging, reverse Jhura Fault underlying the Jhura anticline, a segment of the Kachchh Mainland Fault. This fault segment shows evidence of surface-rupturing earthquakes in the area south of the Great Rann of Kachchh. The investigation reveals three paleoseismic events: Event I before 9.72 ka B.P., Event II between 8.63–8.20 ka B.P., and Event III between 6.20–6.09 ka B.P. The elapsed time since the last event on this fault is > 8000 years, suggesting that the area is exposed to a significant earthquake hazard. This highlights the need for more precise characterization of individual seismogenic sources for future earthquake preparedness. [ABSTRACT FROM AUTHOR]

The Vigukot Fort is in ruins lying along the northern fringe of the Great Rann of Kachchh, Gujarat, India This settlement is located on the left bank of the palaeochannel of the Nara river - a tributary of River Indus. We conducted Real Time Kinematics and Ground Penetrating Radar (GPR) surveys for surface and subsurface. The digital elevation model (DEM) reveals an average elevation ranging from 2 to 4 m from mean sea-level. Two elevated areas: EA1 (site 1) and EA2 (site 2) represent residential areas in the township. EA1 located on higher ground (3-4 m amsl) in the eastern portion comprised of a housing complex of larger dimensions. Two rooms with an area of 650 and 250 sq. ft respectively, possibly indicative of living rooms attached with a courtyard suggest that high-ranked authorities occupied this portion of the township. EA2 with low-elevation (3 m amsl) marked by a smaller residential complex may be indicative of a trade complex along the western flank of the township. On the basis of 3D GPR survey we infer two levels of settlement at EA1 and one level of settlement at EA2. EA1 remained as a residential complex as reflected from both the levels, whereas EA2 was a trading complex close to the main gateway G1. Probably two scenarios prevailed: (1) Both areas flourished likewise at the first level and might have got disturbed by an earthquake; later EA1 may have been reoccupied while EA2 was left to be an open trading complex at the second level (recent). (2) During the first level of occupancy, EA1 was probably a residential complex (having enclosed walls), and EA2 might be the trading complex (with partially enclosed walls lying opposite to G1). Both the areas were affected during the disaster, and the second level of occupancy EA1 was rebuilt and occupied, whereas EA2 was used without renovation. Moreover, the 1819 earthquake probably destroyed both the areas completely and led to their abandonment. [ABSTRACT FROM AUTHOR]

In last 500 years, Kachchh experienced several large magnitude earthquakes (6.0 ≥ M ≤ 7.8), however, not all accompanied surface rupture. The 1819 Allah Bund earthquake (Mw7.8) accompanied surface rupture, whereas, the 2001 Bhuj event (Mw7.6) occurred at a depth of 23 km on E-W striking south dipping thrust fault remained blind. Discontinuities between the denser-brittle basement (?) and overlying ductile-softer Mesozoic-Tertiary-Quaternary succession resulted in a different geometry of faulting. Normal faults associated with rift were reactivated as reverse faults during inversion tectonics, propagated in sedimentary succession and arrested. Thrust-ramps developed along the discontinuities accompanied surface ruptures. Folded structures along the South Wagad Fault (SWF) – an active thrust, exhibits lateral-propagation of fold segments and linkage, suggestive of fault-related-fold growth. Paleoseismic investigations revealed evidence of at least three paleo-earthquakes. Event I occurred before BCE 5080; Event II between BCE 4820 and 2320, and was probably responsible for a massive damage at Dholavira – Harappan site. Event III was between BCE 1230 and 04, most likely caused severe damage to Dholavira. Archaeo-seismological Quality Factor (AQF) of 0.5 suggests that the Dholavira is vulnerable to earthquakes from nearby active faults. With 1500–2000 yr of recurrence interval, occurrence of a large magnitude earthquake on SWF cannot be ruled out. [ABSTRACT FROM AUTHOR]

This communication basically comprise replies to the comments raised by Singh and Rajendran (SR) on our paper Malik et al. (2023) published in Journal of Asian Earth Sciences. We would like to bring to the notice of the readers that our studies and findings are based on a robust methodology towards identification and interpretation of active fault traces. Based on detailed satellite data interpretations, field evidence, paleoseismic studies and GNSS Geodesy data we suggested that Khetpurali Taksal Fault (KTF) is a major fault system with prominent dextral strike-slip motion which marks the segment boundary between the Central and NW Himalaya. Further, an attempt was also made to understand the role of KTF in regional context. We disagree with the claims made by SR. The quires raised by SR are completely baseless and expose their lack of experience and understanding. [ABSTRACT FROM AUTHOR]

The Himalayas, one of the most seismically active regions in the world, experienced several damaging earthquakes in the recent past. Historical data (limited) and paleoseismic studies indicate that some portions of the Himalayas did not rupture during the historic time and have the potential to host major earthquakes. The paleoseismic study was conducted in the mesoseismal zone of the 1905 (Mw7.8) Kangra earthquake, NW Himalaya. Two trenches (ABT1 and ABT2) excavated across the Hajipur Fault (HF2) – an imbricated fault of Himalayan Frontal Thrust (HFT) near Asparbadaliya revealed signatures of at least three paleo-earthquakes, displacing/deforming young Quaternary deposits along NE dipping thrust fault strands (F1 and F2). Exposed stratigraphy in trenches and Optically Stimulated Luminescence (OSL) calibrated/modeled ages suggest that Event I occurred at around BCE 50 - CE 400; Event II was during CE 1450–1670 and Event III at around CE 1720–1840. A larger interval of ∼900–1000 years between Event-I and Event-II suggests that Event-II was a great earthquake with 8.0 ≥ Mw ≤ 8.5 – correlated with CE 1555 earthquake reported from Kashmir with a rupture length of ∼400–450 km, extending from Kashmir to Chandigarh. Event-III that occurred with an interval of 200–300 years was a large earthquake with a magnitude 7.5 ≥ Mw ≤ 8.0, and a rupture length of ∼200–250 km. We propose that the irregular recurrence interval could be attributed to variation in the distribution of fault system between HFT and Main Central Thrust (MCT) in NW (∼100 km) and Central as well as NE Himalaya (∼40–50 km), suggesting heterogeneity exists along the arc. [ABSTRACT FROM AUTHOR]

• Segmentation along Himalayan Arc controls extent of major earthquake ruptures. • Right-lateral Khetpurali Taksal Fault (KTF) marks segment boundary in NW Himalayas. • KTF caused slip-partitioning south of MBT, between thrust and strike-slip faults. • Three paleoearthquakes along KTF, could trigger a major earthquake in future. • The latest event did not rupture the locked part of Main Himalayan Thrust. Northwest Himalaya hosted several major earthquakes, with the most recent 1905 (Mw7.8), exhibits complex distribution of faults along the Nahan Salient and Kangra re-entrant. Geomorphic markers and paleoseismic studies suggest that ∼250 km long out-of-sequence Khetpurali Taksal Fault (KTF), with prominent dextral strike-slip motion, demarcates a segment boundary dividing ∼100 km locked width of Main Himalayan Thrust (MHT) between Central (Kumaon-Garhwal) and NW (Himachal) Himalaya. KTF hosted at least three paleo-earthquakes, Event I: during 6719-4081 BCE; Event II: during 1141-1421 CE – a major event rupturing the entire locked width of MHT displacing the frontal as well as hinterland faults, with a probable rupture length of > 200 km, and Event III - around 1767-1926 CE, which could be 1800 CE or most likely 1905 Kangra earthquake that did not rupture the whole locked part. KTF has displaced Upper-Lesser Himalayan and young Quaternary successions around Nahan Salient, Sundernager Basin, and Kangra re-entrant. It is responsible for the change in structural pattern between Himalayan Frontal Thrust (HFT) and Main Boundary Thrust (MBT), marked by splay faults in Kangra re-entrant (∼100 km wide) lying west of KTF and the Nahan Salient (∼25 km) and Dehradun re-entrant (∼45 km) to the east. KTF located west of the Delhi-Haridwar Ridge (DHR) probably marks a zone of reduced inter-seismic coupling and significant topographic highs in the accretionary wedge, and plays a key role in slip-partitioning between active thrust and oblique (dextral) slip faults, evident by reduced shortening rates in NW as compared to Central Himalaya. [ABSTRACT FROM AUTHOR]