Liquefaction and fluidization of lacustrine deposits from Lahaul-Spiti and Ladakh Himalaya: Geological evidences of paleoseismicity along active fault zone (original) (raw)
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Soil Dynamics and Earthquake Engineering, 2016
Earthquake induced liquefaction features found in the Karewas of Kashmir Valley are potential tools for estimating energy center, magnitude and peak ground acceleration of the paleoearthquakes. Size, pattern and spatial distribution of liquefaction features and in-situ geotechnical data were collected at the paleoliquefaction sites to assess the magnitude and peak ground acceleration of the paleoearthquake. The magnitude of paleoearthquakes was estimated to be of the order of (Mw ¼ 6.2) using "Magnitude bound method" and "In-situ testing of geotechnical properties and assessment of liquefaction potential of liquefied beds (source stratum) using cyclic stress method". The peak ground acceleration computed were in the range of 0.27 g to 0.83 g using cyclic stress method and 0.30 g using attenuation equation NDMA [21]. & 2016 Elsevier Ltd. All rights reserved. 2. Geological and stratigraphic setup of the study area Kashmir Valley is an enclosed basin drained by the river Jhelum along with many major and minor streams. A single fluvial exit from the Kashmir Valley has been cut by river Jhelum through a narrow gorge near the town of Baramulla. The Kashmir Valley is bounded by the Pir Panjal Range (PPR) in south-southwest and the Great Himalayan Range in the east-northeast. The fluvio-glacial and lacustrine deposits of Karewa sediments occurring in the Kashmir Valley are mostly composed of clay, silt, sand, conglomerates, sandy clay, lignite and lignitic mud. These Plio-Pleistocene deposits of Kashmir Valley are the most conspicuous formations spread in the form of mounds, terraces, level lands, dissected plateaus and vast fields starting from Shopian in south Kashmir Contents lists available at ScienceDirect
Earthquake-induced soft-sediment deformation in the lower Shyok river valley, northern Ladakh, India
Journal of Asian Earth Sciences, 2003
Soft-sediment deformation structures occur in the , 150 m thick Pliocene -Quaternary fluvio-lacustrine sediments exposed around the Khalsar and Tirit areas in the lower Shyok river valley, northern Ladakh and eastern Karakoram, India. These structures vary in morphology and pattern and occur at different stratigraphic horizons. They satisfy the criteria for attributing them to seismic events and it is proposed that these structures were formed as a result of earthquake-induced liquefaction. The deformation structures are thus interpreted to represent prehistoric seismic events which occurred up to , 5 Ma ago and were associated with tectonic activity along the Karakoram fault. q
Journal of the Geological Society of India, 2016
The intermontane Karewa basin contains a wide variety of seismically induced soft sediment deformation structures, interpreted as seismites and occurs in 1300 m thick succession of upper and lower Karewas. The Karewa Formation of Kashmir valley are glacio-fluvial-lacustrine and aeolian loess of Plio-Pleistocene age. The soft sediment deformational structures occurs in various formations and members of Karewas and vary greatly in terms of morphology and pattern. The Karewa Formations were frequently confronted with recurrent seismic activities during differential upliftment of Pir Panjal and Zanaskar ranges which resulted in various deformation structures during their evolution and development. In the present study, an attempt has been made to relate the palaeo-seismicity events in Karewa formations with the deformed structures of various formations. The origin of these deformational structures have been interpreted and analyzed from the field evidences by applying paleo-seismological approach. During and after the deposition of Karewas different soft sediment deformation structures (seismites) like load cast, convolute lamination, pseudonodules, recumbent folds, sand dykes etc. were formed during liquefaction and triggered by tectonic impulsive events. The deformational structures are evidenced by their unique nature, distribution, association, behaviour and deformation, and can be used as vital indicators for palaeo-seismicity.
The great 1934 Himalayan earthquake (Mw 8.1) generated a large zone of ground failure and liquefaction in north Bihar, India, in addition to the earthquakes of 1833 (Mw ~7.7) and 1988 (Mw 6.7) that have also impacted this region. Here we present the results of paleo-liquefaction investigations from four sites in the plains of north Bihar and one in eastern Uttar Pradesh. The liquefaction features generated by successive earthquakes were dated at AD 829-971, 886-1090, 907-1181, 1130-1376, 1112-1572, 1492-1672, 1733-1839 and 1814-1854. One of the liquefaction events dated at AD 829-971, 886-1090 and 907-1181 may correlate with the great earthquake of AD ~1100, recognized in an earlier study from the sections across the frontal thrust in central eastern Nepal. Two late medieval liquefaction episodes of AD 1130-1376 and 1492-1672 were also exposed in our sites. The sedimentary sections also revealed sandblows that can be attributed to the 1833 earthquake, a lesser magnitude event compared to the 1934. Liquefactions triggered by the 1934 and 1988 earthquakes were also evident within the topmost level in some sections. The available data lead us to conjecture that a series of temporally close spaced earthquakes of both strong and large types, not including the infrequent great earthquakes like the 1934, have affected the Bihar Plains during the last 1500 years with a combined recurrence interval of 124±63 years.
Evidence of Late Quaternary seismicity from Yunam Tso, Lahaul and Spiti, NW Himalaya, India
Journal of Earth System Science, 2014
A relict fluvio-lacustrine sediment of an 8 m thick section exposed at Kilang Sarai along Yunam river, near Baralacha La shows presence of cycloids or pseudonodules, ball and pillow structures, flame-like and pocket structures, sand dyke injections, bed dislocation/faulting and flow folds. Within this section four deformed levels of soft sediment structures have been identified which were dated ca. 25 ka BP at level 1 (∼0.4 m from the modern river level (mrl), 20.1 ka BP at level 2 (∼1.8 m mrl), 17.7 ka BP at level 3 (∼2.56 m mrl) and 12.2 ka BP at level 4 (∼4.25 m mrl)). Detailed study of these soft sediment structures allow us to demonstrate that deformation level 3 is not related to seismic trigger, but remaining three deformation levels (1, 2 and 4) are ascribed to seismic origin. From compilation of earlier palaeoseismological studies using soft sediment deformational structures (SSDS) in the palaeolake deposits in the adjoining area, suggest that the deformational events identified in the present study are regional in nature and thus tectonic process plays an important role in the evolution of landform in the Spiti region.
Journal of Asian Earth Sciences, 2011
The present article is the first time reporting of a paleoearthquake that occurred during Late Pleistocene time along the Nalagarh Thrust (NT) in the Pinjaur Dun in northwestern sub-Himalaya. Using CORONA satellite photographs, multi-spectral IRS satellite data, and aerial photographs, a prominent active fault has been identified at Nalagarh in Pinjaur Dun. This fault in the alluvial fan is located very close to the NT which borders the topographic front of the Tertiary rocks against Quaternary deposits. A trench excavation survey was carried out at Nalagarh for detailed paleoseismic studies across this thrust fault. Displacing all the lithologic units of the fan sequence, the fault plane has an average dip of 30°due ENE and a vertical displacement of 1.6 m and slip of $2.5 m along the fault. The lithological units, consisting of alternating sand and gravel, show back tilting and asymmetrical tight folding. Based on Optically Stimulated Luminescence (OSL) ages, the oldest litho-unit in the trench is 85.83 ± 7.2 ka and the youngest is 67.05 ± 8.4 ka. The OSL age of the sample collected from the easterly exposure of the fault shows an age of 20 ka. The faulting and associated induced deformation features suggest occurrence of a Late Pleistocene large magnitude earthquake along NT in the Nalagarh region of the Pinjaur Dun following the deposition of the Quaternary sedimentary units. The Late Pleistocene fault substantiates the seismic potential of Pinjaur Dun and calls for more exhaustive study of paleoearthquakes in this fast developing industrial belt and highly populous mountainous region.