recognizing and dating prehistoric liquefaction features lessons learned in the new madrid seismic zone central united states the new madrid seismic zone nmsz which experienced severe liquefaction during the great new madrid missouri earthquakes of 1811 and 1812 as well as during several prehistoric earthquakes is a superb laboratory for the study of world class earthquake induced liquefaction features and their use in paleoseismology in seismically active regions like the nmsz frequent large earthquakes can produce a complex record of liquefaction events that is difficult to interpret lessons learned studying liquefaction features in the nmsz may help to unravel the paleoseismic record in other seismically active regions soil characteristics of liquefaction features as well as their structural and stratigraphic relations to native american occupation horizons and other cultural features can help to distinguish prehistoric liquefaction features from historic features in addition analyses of artifact assemblages and botanical content of cultural horizons can help to narrow the age ranges of liquefaction features future research should focus on methods for defining source areas and estimating magnitudes of prehistoric earthquakes from liquefaction features also new methods for dating liquefaction features are needed

holocene climatic fluctuations in the gujarat alluvial plains based on a multiproxy study of the pariyaj lake archive western india abstract a sediment core from pariyaj lake from the vatrak river basin located at the desert margin in the gujarat alluvial plains of western india was investigated in a multidisciplinary aspect the goal was to reconstruct the palaeoclimate palaeoenvironment and tectonic history and to understand the role these factors played in the geomorphological evolution of the area during the holocene palaeoclimatic interpretations also shed light on the factors responsible for the rise and fall of the harappan civilisation the results obtained based on multiproxy studies show five climatic phases during the last 11 000 yr bp phase 1 11 000 cal yr bp represents a very humid climate and high precipitation discharge leading to high lake stand as attested by the high pollen concentration of semi evergreen tree taxa phytoliths belonging to cool and moist grasses and large proportion of algae marking the onset of holocene in phase 2 8000 to 9000 cal yr bp a significantly reduced yield of pollen phytoliths and aquatic algae indicates shrinkage of the lake phase 3 7630 cal yr bp shows moderate yield of pollen and phytolith pointing towards fluctuating precipitation conditions phase 4 5864 to 4680 cal yr bp shows very low pollen and phytolith counts indicating a very dry spell finally phase 5 4680 to 3500 cal yr bp shows a good density and diversity of flora the wet climate and high lake stand 11 000 cal yr bp 7630 cal yr bp and after 4680 cal yr bp are synchronous with the lacustrine marine and aeolian records of western india the contribution of winter precipitation at 7630 cal yr bp and after 4680 cal yr bp can be correlated with similar records from rajasthan lake decrease in the precipitation activity the low lake stand and the onset of dry climatic condition between 8000 and 9000 cal yr bp corresponds to a near global anomaly of this period another dry event between 5864 and 4680 cal yr bp documented in pariyaj lake record is synchronous with various proxy records of the mid late holocene afro asiatic monsoonal belt

rift basins in western margin of india and their hydrocarbon prospects with special reference to kutch basin the western continental margin of india can be classed as a divergent or passive margin the western continental shelf is an extensive carbonate bank bombay offshore basin passing into clastic sediments on the north and south three craton margin embayed basins kutch cambay and narmada in the northern part of the shelf are filled predominantly with clastic sediments these basins occupy grabens bounded by faults diverging seaward the grabens were formed by three rift systems along major precambrian tectonic trends the rifting developed sequentially from north to south around the saurashtra horst kutch basin was formed in the early jurassic followed by cambay basin in early cretaceous time and the narmada in the late cretaceous it appears that these rifting ev nts occurred at successive stages during the northward migration of the indian plate after its break from gondwanaland in late triassic or early jurassic it is inferred that these rift basins opened up successively as a result of the counterclockwise drift of the indian craton bombay offshore and cambay are two major oil producing basins in the western margin these basins are characterized by high geothermal gradients attributed to the shallowness of the mantle in this region oil has not been found in kutch basin which is mainly an onshore mesozoic basin the basin depocenter shifted offshore at the northwestern part of the continental shelf where the shelf is wide

holocene paleoclimates of india we present a comprehensive summary of the available palaeoclimate records from india and compare the results from different proxies the results indicate i fluctuating lake levels during the early holocene the period of relatively higher lake levels from increased precipitation efficiency was reached only 7 2 6 0 cal kyr bp possibly due to increased contribution from winter rainfall ii the onset of aridity in nw india could have begun as early as 5 3 cal kyr bp subsequently there were multiple wet events but of shorter duration and smaller magnitude than during the mid holocene iii there is evidence of several short term climate events in the proxy record however in the absence of a rigorous chronological framework a detailed regional correlation is not possible at this stage finally a comparison between marine and terrestrial records indicates that episodes of strongest and weakest monsoon winds were not always associated with wettest and driest episodes respectively in the nw indian lakes

chronology of late pleistocene environmental changes in the lower mahi basin western india sediments exposed in the lower mahi basin at the southern fringe of the thar desert rajasthan india provide evidence of three distinct depositional environments namely marine aeolian and fluvial these have been used to reconstruct late pleistocene environmental and tectonic history of the region infrared stimulated luminescence irsl chronology of the fluvial and aeolian litho units provides evidence of two major fluvial aggradation phases in the region corresponding to oxygen isotopic stages 5 and 3 the basal marine clay is inferred to represent the last interglacial stage and its present elevation at 20 m a s l is attributed to post depositional tectonism comparison of fluvial records from other regions indicates interhemispherically documented wetter phases during oxygen isotope stages 5 and 3 copyright 2000 john wiley sons ltd

abrupt weakening of the summer monsoon in northwest india 4100 yr ago climate change has been suggested as a possible cause for the decline of urban centers of the indus civilization 4000 yr ago but extant paleoclimatic evidence has been derived from locations well outside the distribution of indus settlements here we report an oxygen iso tope record of gastropod aragonite 18 o a from holocene sediments of paleolake kotla dahar haryana india which is adjacent to indus settlements and documents indian summer mon soon ism variability for the past 6 5 k y a 4 increase in 18 o a occurred at ca 4 1 ka mark ing a peak in the evaporation precipitation ratio in the lake catchment related to weakening of the ism although dating uncertainty exists in both climate and archaeological records the drought event 4 1 ka on the northwestern indian plains is within the radiocarbon age range for the beginning of indus de urbanization suggesting that climate may have played a role in the indus cultural transformation

landform development in a zone of active gedi fault eastern kachchh rift basin india abstract an earthquake of 2006 mw 5 7 occurred along east west trending gedi fault gf to the north of the kachchh rift basin in western india which had the epicenter in the wagad upland which is approximately 60 km northeast of the 2001 mw 7 7 earthquake site or epicenter development of an active fault scarp shifting of a river channel offsetting of streams and uplift of the ground indicate that the terrain is undergoing active deformation based on detailed field investigations three major faults that control uplifts have been identified in the gf zone these uplifts were developed in a step over zone of the gf and formed due to compressive force generated by left lateral motion within the segmented blocks in the present research a terrace sequence along the north flowing karaswali river in a tectonically active gf zone has been investigated reconstructions based on geomorphology and terrace stratigraphy supported by optical chronology suggest that the fluvial aggradation in the wagad area was initiated during the strengthening at 8 ka and declining 4 ka of the indian summer monsoon ism the presence of younger valley fill sediments which are dated 1 ka is ascribed to a short lived phase of renewed strengthening of ism before present day aridity based on terrace morphology two major phases of enhanced uplift have been estimated the older uplift event dated to 8 ka is represented by the tertiary bedrock surfaces which accommodated the onset of valley fill aggradation the younger event of enhanced uplift dated to 4 ka was responsible for the incision of the older valley fill sediments and the tertiary bedrock these ages suggest that the average rate of uplift ranges from 0 3 to 1 1 mm yr during the last 9 ka implying active nature of the area

chronology and rates of faulting of ventura river terraces california new evidence concerning the chronology of four late pleistocene terraces of the ventura river near oak view california that are vertically offset and tilted by reverse and reverse flexural slip faults provides a means of estimating rates of fault movement and downcutting by the ventura river radiocarbon ages of charcoal contained within terrace deposits date two of the terraces correlation of soils that have developed on terrace deposits and extrapolation of the rate of vertical displacement of the arroyo parida santa ana fault not a flexural slip fault date the others resulting age estimates for the four main late pleistocene terraces are qt5b 30 000 qt6a 38 000 qt6b 54 000 and qt6c 92 000 yr b p vertical slip rates on flexural slip faults range from 0 3 to 1 1 mm yr and apparently are related to the rate form and mechanics of folding of the north limb of the ayers creek canada larga syncline average rates of downcutting of the ventura river for several intervals during the late pleistocene estimated from the chronology and relative elevation of river terraces north of the arroyo panda santa ana fault upstream from the zone of faulting vary from 0 5 to 1 3 mm yr the range in rates probably reflects variations in local uplift as well as adjustments to changing eustatic sea level climatic conditions and or regional deformation of the western transverse ranges the average rate of downcutting of the ventura river north of the zone of flexural slip faulting is 0 8 mm yr compared with 1 2 to 2 2 mm yr in the deformation zone immediately to the south this apparently indicates that during tectonic deformation there is an approximate balance between the rate of uplift due to faulting and folding and the rate of downcutting by the fluvial system

fluvial response to late quaternary climate changes western india we review here the fluvial response to late quaternary climatic changes in the semi arid regions of western india i e the thar desert and its margins and maharashtra the rivers in the thar desert show a spectrum of environments from gravel bedload braided to ephemeral sand bed streams to sheet flows and sheet floods while those in the thar margin and maharashtra show dominantly two modes i e braided and meandering rivers the streams became defunct and aeolian sands were deposited during periods of relatively greater aridity in the thar desert and its margins incisions occurred during the wet phases in ois 1 it is inferred that changes in the monsoon precipitation led to relative changes in the discharge and sediment supply which were routed through those in the vegetation cover and played a key role in determining the fluvial style an inter comparison of the late quaternary alluvial deposits in the semi arid regions of western india suggests a continuum of fluvial environments interrelated through a precipitation gradient further a global comparison indicates that the response of semi arid western indian rivers was synchronous with the rivers in other climatic settings

fluvial systems of the drylands of western india a synthesis of late quaternary environmental and tectonic changes abstract the fluvial systems and landscape of the drylands of western india have preserved evidence of late quaternary environmental and tectonic changes data on the fluvial systems of mainland gujarat saurashtra and kachchh have been synthesised to evaluate the roles of geological factors in the evolution of these drylands mainland gujarat is largely underlain by the flat alluvial plain and has a structurally controlled fluvial system that originates in the eastern uplands the fluvial system of mainland gujarat shows deeply incised valleys entrenched meanders extensively developed ravines and uplifted terraces which have preserved a late quaternary succession of continental fluvial and aeolian and marine sediments dating back to 125 ka marine sediments correspond to the transgressive phases of the last interglacial 125 ka and post glacial maximum 6 ka the overlying alluvial sediments suggest deposition by ephemeral rivers in varied fluvial depositional environments under a semi arid to sub humid climatic regime with periods of intense pedogenesis the sedimentation can be correlated with marine isotopic stages mis 5 and 3 the fluvial sediments are buried under a thick blanket of aeolian sediments which are indicative of enhanced dune building activity in the thar desert and are correlatable to the global arid phase of the last glacial maximum the post aeolian tectonic uplift triggered severe erosion of late pleistocene sediments and 40 50 m deep incised fluvial valleys were formed this erosional phase suggests a resumption of fluvial activity which coincided with the rapidly rising sea level on the west coast during the early holocene the holocene marine and fluvial aggradation was initiated within the incised fluvial valleys around 6 ka and continued uninterrupted until 2 ka these sediments now occur as raised valley fill terraces suggesting a late holocene uplift further corroborated by low to moderate seismic activity during historical times the landscape of saurashtra is marked by flat topped basaltic trappean ridges and a highly varied coastline where a narrow belt of low ridges and cliffs of miliolite limestones and other shore deposits are found the fluvial system of saurashtra shows a radial drainage pattern the channels have steep banks in the hilly regions and show significant deflections before meeting the sea evidence of last interglacial high sea levels 125 ka are found on the coastal cliffs of southern saurashtra in the form of oyster reefs and notches of various types which now occur at higher levels a net sea level rise of 7 m consistent with the global sea level estimates at 125 ka has been obtained by recent studies after decoupling the tectonic component dating of late pleistocene and holocene sea levels on this coast suggest continued uplift of saurashtra since 125 ka even though the sea level continued to fluctuate the holocene high sea submerged a considerable stretch of land including the okha rann on the northern saurashtra coast and isolated patches in and around the river mouths on the southern coast the short straight and parallel courses of rivers in the direction of tectonic slope incised and confined channel belts also suggest a strong component of tectonic uplift the continental sediments exposed in these river valleys have however remained uninvestigated leading to lack of palaeoclimatic data a remarkable control of structure on landscape evolution is depicted by the kachchh peninsula the fluvial system exhibits the characteristics of drainage flowing along tectonically provided slopes the overall drainage pattern of kachchh shows excellent correlation with n s trending transverse fault patterns the transverse fault system has brought out changes in the landscape of kachchh though the kachchh rift basin evolved along e w latitudinal faults the quaternary deposits occur in the form of miliolite limestones colluvial and alluvial fans fluvial sands and silts and rann sediments significant sedimentologic details on these sediments are lacking however the marine incursions seem to correlate with the adjacent saurashtra and mainland gujarat

evidence of enhanced winter precipitation and the prevalence of a cool and dry climate during the mid to late holocene in mainland gujarat india the kothiyakhad sedimentary sequence of mahi estuary in mainland gujarat india contains valuable information on late to mid holocene climatic conditions as inferred by phytolith palynofacies magnetic susceptibility and clay mineralogical studies three distinct climatic regimes ie phase i ii and iii were established phase i 3660 3400 yr bp shows a gradual weakening of sw monsoonal activity though overlapped by enhanced western disturbances which led to the development of cool climatic conditions the coupled effect of sw monsoon and enhanced winter precipitation produced improved hydrological conditions which supported the agrarian society of the indus valley civilization until the beginning of phase ii 3400 3000 yr bp during phase ii the sw monsoon was in a state of severe recession leading to severe drought like conditions other than for a brief but intensely warm and humid pulse recorded at 3320 yr bp associated with sw monsoonal activity in phase iii 3000 2850 yr bp sw pre

quaternary climate change and the formation of river terraces across growing anticlines on the north flank of the tien shan china nested stream terraces warped upward over actively growing anticlines along the north flank of the tien shan in western china appear to record alternating phases of valley widening and incision differences of relative heights between remnants of four separate strath terraces along one river and between two such terraces along another reach 100 to 120 m over the crests of the anticlines we infer that this spacing is due to alternating stages of valley widening and rapid incision associated with climate changes with a periodicity of 100 kyr the crests of the anticlines appear to emerge from the aggrading flanks of the anticlines at an average rate of about 1 mm a the maximum heights of 25 and 35 10 m for the lowest terraces above their projected initial profiles imply ages of roughly 25 kyr and 35 kyr 10 kyr hence they suggest that flood plains which were abandoned to form the terraces developed adjacent to active stream beds during the last glacial period when climates were relatively

late quaternary climate and seismicity in the katrol hill range kachchh western india abstract a channel fill sequence in the upper catchment of the khari river in the south of the katrol hill fault khf has been investigated to understand the role of climate and tectonics in the evolution of fluvial landforms detailed sedimentology and limited optical chronology suggest that the channel incision occurred during weak summer monsoon prior to 19 9 ka and is attributed to the activity along the khf and its subsidiary faults the post glacial to early holocene was a phase of landscape stability subdued tectonics which persisted until around 7 1 ka particularly between 9 4 ka and 7 1 ka an enhanced monsoon activity is inferred a renewed phase of uplift is suggested after 7 1 ka that probably continues till present

archeological and pedological evidence for large prehistoric earthquakes in the new madrid seismic zone central united states prehistoric liquefaction features have been identified by careful observation of their structural and stratigraphic relations to native american occupation horizons and their subtle soil characteristics the ages of these liquefaction features have been estimated from radiocarbon dating of wood associated with the features and native american artifacts found within bounding occupation horizons at three sites near blytheville arkansas in the central part of the new madrid seismic zone one sand blow crater formed between a d 800 and 1400 two sand blow deposits formed between a d 800 and 1670 and three possibly four sand dikes formed since 4035 b c where not found in association with native american occupation horizons and artifacts prehistoric liquefaction features can be difficult to distinguish from features that formed during the great new madrid earthquakes of a d 1811 and 1812 this raises the possibility that prehistoric liquefaction features may have been misinterpreted during previous studies in the area nevertheless a paleoearthquake chronology is beginning to emerge for the new madrid seismic zone our findings are consistent with paleoseismological studies in the northern part of the seismic zone and suggest a recurrence interval of hundreds of years for earthquakes large enough to induce liquefaction in this region m 6 4 by mapping the age distribution of liquefaction features a more accurate assessment of the long term earthquake potential of the region will be possible

aggradation history and luminescence chronology of late quaternary semi arid sequences of the sabarmati basin gujarat western india the gujarat alluvial plain in the semi arid desert margin of the thar desert contains a record of continental quaternary sequences these sequences were built by drainages originating in the aravalli hills and flowing westward into the indian ocean stratigraphic studies of a part of the late quaternary succession in the sabarmati basin have resulted in a fourfold lithostratigraphic scheme the waghpur formation conglomeratic member sand member the mahesana formation lower heterolithic member upper sand member the akhaj formation and the sabarmati formation facies analysis distribution of conglomerates and cross bed azimuths of the clastic facies of the waghpur formation were used to infer ne sw trending semi arid alluvial fans the deposition of the overlying heterolithic member took place in ephemeral streams influenced by episodic flows and aeolian reworking the upper member of the mahesana formation represents aeolian and older levee deposits feasibility studies of thermoluminescence tl and infra red stimulated luminescence irsl dating on the sabarmati succession yielded stratigraphically consistent ages ranging from 5 ka to 300 ka for two samples tl ages on quartz and irsl ages on feldspar separates were consistent these results together with the stratigraphic and petrographic data reveal the following events in the accumulation history of the sabarmati sequence 1 1 significant aggradation at 300 ka gravel sand and at 58 ka sand and 2 2 pedogenesis bracketed to 58 39 ka the sabarmati river in its middle stretches follows a regional slope deviatory course interpreted previously to be a neotectonic adjustment within the cambay graben our chronological data suggest that this adjustment occurred possibly within the past 39 ka

mid late holocene monsoonal variations from mainland gujarat india a multi proxy study for evaluating climate culture relationship a multi proxy study involving palynology phytoliths sedimentology clay mineralogy carbon isotopes and magnetic mineralogy was carried out on wadhwana lake sediments from sub humid zone of mainland gujarat to determine the mid holocene climatic fluctuations and its possible impact on the harappan culture the 1 03 m sediment profile of wadhwana lake shows five paleoclimatic phases the study reveals high lake stand during phase i 7500 5560 cal yr bp a considerable cool and moist climatic condition during phase i is inferred due to the presence of pollen belonging to wet evergreen taxa and high phytolith climatic index ic later part of phase i show gradual replacement of evergreen to deciduous pollen taxa decrease in ic value and dominance of smectite over kaolinite indicating a reduction in wet climatic condition due to decline in the precipitation and prevalence of seasonally dry climate however a large variety of madhuca meliaceae asteraceae pollen taxa abundant fresh water algae chrozophora and ceralia pollen in this period provides evidence of intensified arboriculture and agricultural activity low lake level and dry climate have been documented during phase ii 5560 to 4255 cal yr bp and are synchronous with the lake records of western indian region high values of phytolith aridity index iph high primary minerals increase in the i 13c values provide evidence for excessive dry climatic conditions at 4255 cal yr bp phase iii shows a gradual strengthening of sw monsoon after 3500 cal yr bp phase iv shows a short pulse of dry climatic conditions 3238 to 2709 cal yr bp followed by somewhat similar to present day climate for phase v the study concludes that onset of dry climate after 5500 cal yr bp is a regionally spread synchronous event that has been documented in several lake records of western india it is surmised that the urbanization in harappan civilization in north west india was coincident with the initial phase of declining rainfall of mid holocene the emergence of cultural complexity of harappan civilization should be seen as an initial adaptation to earliest phase of environmental deterioration and its subsequent decline is probably linked with the changing seasonality pattern and excessive dry climate of later phase 4200 4255 cal yr bp of mid holocene

luminescence chronometry and geomorphic evidence of active fold growth along the kachchh mainland fault kmf kachchh india seismotectonic implications abstract the kachchh region of western india is a pericratonic basin experiencing periodic high magnitude earthquakes events in 2001 a catastrophic seismic event occurred at bhuj measuring mw 7 7 the epicenters of both the 1956 and 2001 earthquakes were along the kachchh mainland fault kmf proximal to the eastern end of the northern hill range nhr the latter is a topographic expression of an active fault related fold on the hanging wall and is controlled by a south dipping blind thrust the present study deals with the eastern sector of nhr and uses optical dating to reconstruct the chronology of tectonically caused incisions along the backlimb of the nhr incision ages on channel fills and valley fill terraces progressively decrease from 12 ka to 4 3 ka this age progression along with geomorphic evidences decrease in topographic relief drainage capture and drainage migration across the fold nose suggests an active vertical and lateral fold growth along the kmf optical ages suggest that during the late holocene the average uplift rate along the eastern nhr was 10 1 mm a recent gps based estimates on crustal shortening are 12 mm a the kmf and the south wagad fault swf represent the bounding faults of a transtensional basin that formed during the initial rifting this basin is termed as the samakhiali basin the compressive stresses on account of structural inversion from normal to reverse phase resulted in lobate shaped anticlines along kmf and swf zone these anticlines subsequently coalesced and formed linked and overlap segments the present study suggests that eastward lateral deformation across the eastern portion of kmf has continued and has now resulted in its interaction with a left step over transfer fault called the south wagad master fault swmf this implies an increasing transpersional deformation of the samakhiali basin we therefore suggest that the eastward nhr ridge propagation along kmf resulted in the thrust faulting on the south dipping swmf resulting in the bhuj 2001 event the increasing strain on this basin may cause enhanced seismicity in the future along the eastern kmf and wagad region

long river profiles tectonism and eustasy a guide to interpreting fluvial terraces along three rivers at the mendocino triple junction northern california strath cut and fill terraces have formed in response to tectonic and eustatic processes detailed surveying and radiometric dating at multiple sites indicate that lower reaches of the rivers are dominated by the effects of oscillating sea level primarily aggradation and formation of fill terraces during sea level high stands alternating with deep incision during low stands a eustasy driven deposi tional wedge extends tens of kilometers upstream on all rivers tapering to zero thickness this distance is greater than expected from studies of the effects of check dams on much smaller streams elsewhere due in part to the large size of these rivers however the change in gradient is nearly identical to other base level rise studies the depositional gradient is about half that of the original channel middle to upper reaches of each fiver are dominated by the effects of long term uplift primarily lateral and vertical erosion and formation of steep unpaired strath terraces exposed only upstream of the depositional wedge vertical incision at a rate similar to that of uplift has occurred even during the present sea level high stand along rivers with highest uplift rates strath terraces have steeper gradients than the modem channel bed and do not merge with marine terraces at the river mouth consequently they cannot be used to determine altitudes of sea level high stands strath formation is a continuous process of response to long term uplift and its occurrence varies spatially along a river depending on stream power and hence position upstream strath terraces are found only along certain parts of a coastal stream upstream of the aggradational effects of oscillating sea level and far enough downstream that stream power is in excess of that needed to transport the prevailing sediment load for a given size fiver the greater the uplift rate the greater the rate of vertical incision and consequently the less the like lihood of strath terrace formation and preservation

geologic evidence for recurrent moderate to large earthquakes near charleston south carolina multiple generations of earthquake induced sand blows in quaternary sediments and soils near charleston south carolina are evidence of recurrent moderate to large earthquakes in that area the large 1886 earthquake the only historic earthquake known to have produced sand blows at charleston probably caused the youngest observed blows older late quaternary sand blows in the charleston area indicate at least two prehistoric earthquakes with shaking severities comparable to the 1886 event

mid holocene sedimentation and landscape evolution in the western great rann of kachchh india abstract this study is an attempt to reconstruct the history of sedimentation and landform evolution in the western great rann of kachchh field stratigraphy sedimentology geochemistry optical and radiocarbon dating suggest dominance of tidal flat sedimentation with subordinate contribution coming from the southern draining streams during 5 5 to 2 ka variability in the geochemical proxies are interpreted as a surrogate for tidal energy viz zr and cr which along with the major elemental ratios tio 2 al 2 o 3 and k 2 o al 2 o 3 indicate enhanced tidal energy condition during 5 5 to 5 ka and around 3 ka a close correspondence of the major and trace elements with those of the indus river sediment and the dominance of illite suggest the indus river was a major contributor for western rann sedimentation during the mid holocene these sediments were routed through the kori creek during marginally high sea level until around 2 2 ka and the present landscape was largely sculptured after the 1819 allah bund earthquake

holocene tectonic activity along kachchh mainland fault impact on late mature harappan civilization kachchh western india abstract paleoseismic and archaeological records of the kachchh rift basin krb of western india indicates that the region become tectonically active during the period of middle to late holocene to understand the relationship between strain accumulation earthquake genesis and landform development we analyzed uplifted late quaternary terraces and archaeological evidence along the kachchh mainland fault kmf zone dividing the elevation of the bedrock strath at each site by their ages yields vertical uplift rates of 0 29 1 17 mm y for the kmf zones archaeological data from the excavation of the kotada bhadli site suggest that the site was occupied during the late mature harappan 2300 2500 bce period and abandoned around 1900 bce the ruins of harappan civilization at kotada bhadli location are resting over the middle holocene fluvial sediments the oldest fluvial sediment is dated to 4 ka whereas the youngest sediment yielded an age of 3 ka the chronological constraints in geomorphic and archaeological records suggest that the area was hit by an earthquake around 2200 bc 3 5ka the geomorphic and chronologically constrained uplift rates reveal that the kmf zone of the intraplate region of the kachchh is geodynamically controlled by several fault segments which are consistent with the ambient tectonic stress field owing to the northward movement of the indian plate concerning the eurasian plate

characteristics of deformation and past seismicity associated with the 1819 kutch earthquake northwestern india the 1819 earthquake in kutch northwestern india is one of the most significant events to have occurred in a plate interior setting despite being the second largest among the stable continental region scr earthquakes this event has not been analyzed within the context of present day understanding of earthquake seismology coseismic changes related to this earthquake include massive ground deformation in a wide low lying tidal flat area although detailed historic accounts of this earthquake exist many questions regarding the mode of deformation and the seismic history of the region remain unresolved we explored the region nearly 180 years after the earthquake and the information gathered adds to our understanding of this event and provides a fresh perspective on this unique intraplate seismogenic zone a 90 km long tract of elevated land with a peak height of 4 3 m is the most visible surface expression of this earthquake we surveyed and analyzed the morphological features of this scarp and also carried out exploratory trenching in this region the scarp morphology is suggestive of a growing fold related to a buried north dipping thrust rather than a discrete fault that could have resulted from a surface rupture the extensive liquefaction field associated with the earthquake offered an ideal setting to explore the paleoearthquake history age data of liquefaction features suggest that a previous event of comparable size must have occurred 800 1000 years ago seismic activity appears to be related to the reactivation of an ancient rift in a stress regime that is dominated by nearly north south compression

assessing the previous activity at the source zone of the 2001 bhuj earthquake based on the near source and distant paleoseismological indicators 1 the m w 7 7 2001 bhuj kachchh earthquake was not associated with any primary surface rupture but it produced secondary faulting folding and liquefaction this study highlights the potential of a secondary rupture and proxies like lateral spreads and sandblows in unraveling the past activity related to the 2001 source chronological constraints of an older lateral spread and far field paleoliquefaction features combined with archeological data provide evidence for occurrences of two previous earthquakes at the 2001 source zone about 4000 and 9000 years ago distinct stratigraphic evidence for at least one previous offset dated at 4424 656 years could be detected at a stepover zone associated with a dextral secondary fault reactivated during the 2001 earthquake the studies imply longer interseismic intervals for the 2001 source zone in comparison with the source zone of the 1819 earthquake located toward the northwestern part of the rann of kachchh the spatial and temporal correlation of previous events derived on the basis of the available paleoseismic data from the region suggest not only repeated activity at the 2001 source but possibility for additional potential sources in parts of kachchh and cambay basins although we infer a longer recurrence interval for the 2001 bhuj earthquake source our study points to the fact that these additional sources may have the potential to rupture in the future considering the long elapsed time

continental record of the southwest monsoon during the last 130 ka evidence from the southern margin of the thar desert india abstract field stratigraphy sedimentology and luminescence dating of the exposed fluvial and aeolian sequences from the southern desert margin were used to discern the pattern of southwest monsoon variability during the last 130 ka the sedimentary architecture and textural attributes of the sediments belonging to the period 130 120 ka suggests the existence of a meandering river system consequent to enhanced southwest monsoon conditions a shift from a meandering to a braided pattern during 120 100 ka indicates a phase of reduced precipitation presence of flood plain fines and bedded calcretes during 100 70 ka suggest a period of enhanced monsoon with seasonality following this a phase of weak monsoon activity was observed during 70 60 ka regional flood plain aggradation and pedogenesis during the period termination of a regional fluvial phase around 30 ka and incision of dunes dated to 20 11 ka suggest that the present rivers occupied their course between 11 ka drowned valleys in the estuarine zones suggest that the incision began during the low sea stand around 20 ka when the rivers were graded to the exposed shelf the incision intensified with the re establishment of monsoon during the early holocene

abrupt changes in the asian southwest monsoon during the holocene and their links to the north atlantic ocean during the last ice age the indian ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial scale climate events in the north atlantic region1 2 3 suggesting a mechanistic link in the holocene epoch which had a more stable climate the amplitude of abrupt changes in north atlantic climate was much smaller and it has been unclear whether these changes are related to monsoon variability here we present a continuous record of centennial scale monsoon variability throughout the holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic arabian sea our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the north atlantic region4 including the most recent climate changes from the medieval warm period to the little ice age and then to the present we therefore suggest that the link between north atlantic climate and the asian monsoon is a persistent aspect of global climate

the 26 january 2001 m 7 6 bhuj india earthquake observed and predicted ground motions although local and regional instrumental recordings of the devastating 26 january 2001 bhuj earthquake are sparse the distribution of macroseismic effects can provide important constraints on the mainshock ground motions we compiled available news accounts describing damage and other effects and interpreted them to obtain modified mercalli intensities mmis at 200 locations throughout the indian subcontinent these values are then used to map the intensity distribution throughout the subcontinent using a simple mathematical interpolation method although preliminary the maps reveal several interesting features within the kachchh region the most heavily damaged villages are concentrated toward the western edge of the inferred fault consistent with western directivity significant sediment induced amplification is also suggested at a number of locations around the gulf of kachchh to the south of the epicenter away from the kachchh region intensities were clearly amplified significantly in areas that are along rivers within deltas or on coastal alluvium such as mudflats and salt pans in addition we use fault rupture parameters inferred from teleseismic data to predict shaking intensity at distances of 0 1000 km we then convert the predicted hard rock ground motion parameters to mmi by using a relationship derived from internet based intensity surveys that assigns mmi based on the average effects in a region the predicted mmis are typically lower by 1 3 units than those estimated from news accounts although they do predict near field ground motions of approximately 80 g and potentially damaging ground motions on hard rock sites to distances of approximately 300 km for the most part this discrepancy is consistent with the expected effect of sediment response but it could also reflect other factors such as unusually high building vulnerability in the bhuj region and a tendency for media accounts to focus on the most dramatic damage rather than the average effects the discrepancy may also be partly attributable to the inadequacy of the empirical relationship between mmi and peak ground acceleration pga when applied to india the mmi pga relationship was developed using data from california earthquakes which might have a systematically different stress drop and therefore a different frequency content than intraplate events when a relationship between response spectra and mmi is used we obtain larger predicted mmi values in better agreement with the observations

flow in the neighborhood of a confined aquifer observation well summary an analytical solution for flow in the vicinity of an observation well is developed the observation is emplaced in a homogeneous aquifer of infinite radial extent that is pumped at a constant rate and satisfies the theis solution we attempt to account for the effect of an observation well on the drawdown response in a neighborhood of finite radial extent centered around the well the model of black and kipp black j h kipp jr k l 1977 observation well response time and its effect upon aquifer tests journal of hydrology 34 297 306 only makes a correction to the drawdown response at the well location and does not modify the flow pattern in the neighborhood of the well this may be sufficient for isolated observation wells but for well fields or sites with relatively closely spaced wells the flow patterns in the neighborhoods of the wells may significantly impact drawdown response the model we develop is applied to field data and is shown to yield an aquifer hydraulic diffusivity that is comparable to that estimated with the model of black and kipp black j h kipp jr k l 1977 observation well response time and its effect upon aquifer tests journal of hydrology 34 297 306 in addition to providing estimates of formation conductivity and specific storage the solution yield estimates of the hydraulic conductivity and specific storage of the zone of influence and has the ability to predict the effect of the observation well on drawdown response in a finite region of influence in the vicinity of the well

active segmentation assessment of the tectonically active south wagad fault in kachchh western peninsular india abstract in present study the results of integrated studies of landform development and geomorphic indices of drainage networks across the south wagad fault swf zone have been presented the swf is a structure that is morphogenic in nature creating a 40 m high e w trending escarpment that extends 80 km at the southern end of the wagad uplift the swf got reactivated during the bhuj earthquake of 2001 continued aftershock activity of m 4 levels were recorded in the epicentral zone north of the kachchh mainland fault and west of the swf strath terraces along the river valleys and the truncation of alluvial fans along the mountain front incision and offset of rivers suggests an active nature of the swf to assess the relative tectonic activity morphometric indices such as stream gradient sl index hypsometric integral hi basin asymmetry af mountain front sinuosity smf index sinuosity index si and basin shape bs have been analyzed the landform development along the river valley in the swf zone suggests reactivation of the swf between 12 and 3 ka the southern front of wagad is found to be uplifting at the rate of 2 8 mm y during the last 12 ka as estimated through osl dates the relative index of active tectonics riat by the study of different geomorphic parameters and field checks indicates that most of the wagad highland is active the compressional strain of 0 05 strain y inferred from the gps study in the swf area attests to the activeness

fluvial geomorphology and neotectonic activity based on field and gpr data katrol hill range kachchh western india abstract the largely rocky and rugged landscape of the katrol hill range composed of mesozoic rocks and structurally controlled occurrences of quaternary sediments is delimited to the north by north facing range front scarps of the seismically active e w trending katrol hill fault khf the landscape and drainage characteristics of the katrol hill range are documented together with ground penetrating radar gpr investigations along the khf to delineate its nature for understanding neotectonic activity in the contemporary tectonic setting the overall geomorphology is controlled by the south oriented tilt block structure of the range indicated by its pronounced influence on the morphology and drainage network the drainage comprises north flowing and south flowing rivers with the drainage divide located close to the northern edge of the range which also marks the highest topographic elevations the narrow zone between the crest line and the drainage divide has been identified as the zone of gorges where gorges and deeply incised fluvial valleys have been formed within quaternary sediments by the various north flowing streams the quaternary sediments consist of bouldery colluvial deposits in front of the range front scarps valley fill miliolites and alluvial deposits of late pleistocene age within the back valleys and scarp derived colluvium forming the youngest deposit based on the geomorphic and stratigraphic evidence three major phases of quaternary tectonic uplift in the katrol hill range are inferred the oldest pre miliolite phase middle pleistocene was followed by a prominent phase of fluvial incision with formation of gorges during early holocene and then by the last one during late holocene continuing at present uplift of the range occurred in well marked phases during the quaternary in response to differential uplift along the khf under an overall compressive stress regime gpr investigations at selected sites show that the khf is a steep south dipping reverse fault near the surface which becomes vertical at depth this suggests neotectonic reactivation of the khf under a compressive stress regime responsible for active southward tilting of the katrol hill range

fluvial landforms and their implication towards understanding the past climate and seismicity in the northern katrol hill range western india abstract the tectonically active kachchh peninsula in western india lies in the southwest monsoon trajectory and hence provides a rare opportunity to decipher the temporal changes in climate tectonics interaction in the evolution of the fluvial landforms reconstructions based on geomorphology sedimentology and geochemistry supported by optical chronology suggest that the fluvial aggradation in the region was initiated during the onset of the indian summer monsoon ism after the last glacial maximum lgm the sedimentary characteristics and major elemental concentrations suggest that the sediments are dominated by fluvially reworked miliolites with subordinate contribution from the mesozoic sandstones and shales and were deposited with the initiation of the ism after the lgm temporal changes in facies architecture and major element concentrations suggest a progressive strengthening of the monsoon between 17 and 12 ka this was succeeded by an overall strengthened ism phase with fluctuations after 12 ka and based on the morphology of the fluvial landforms two major events of enhanced uplift can be suggested the geomorphic expression of the older uplift event dated to 17 ka is represented by the beveled mesozoic bedrock surfaces which accommodated the post lgm valley fill aggradation the younger event of enhanced uplift which is assigned to

characterization of the causative fault system for the 2001 bhuj earthquake of mw 7 7 abstract precise hypocenters erh m w 2 0 5 3 delineate a east west trending blind thrust dipping 45 towards south named as north wagad fault nwf about 25 km north of kachchh main land fault kmf as the causative fault for the 2001 bhuj earthquake of m w 7 7 the aftershock zone involves a crustal volume of 60 40 35 km 3 lying between kmf and nwf the waveform inversion of 45 aftershocks of m 3 0 5 3 suggest that the e w trending south dipping reverse faulting mainly characterizes the aftershock zone however some reverse faulting along nw se as well as ne sw planes and some strike slip faulting along nw se trending vertical plane are also noticed the estimated p axes point on an average towards n s while t axes orient in e w agreeing well with the prevailing regional plate tectonic stress directions the estimated velocity model from one dimensional inversion of 8000 p and 5000 s travel times from 600 aftershocks deciphers a detailed crustal structure of the region upper 0 6 km on an average suggests a low velocity zone characterizing the jurassic and younger sediments the depth range 6 42 km is characterized on an average by larger values of v p 6 31 to 6 98 km s with an average of 6 71 km s v s 3 64 to 4 05 km s with an average of 3 85 km s and v p v s 1 69 to 1 81 with an average of 1 75 the high crustal velocities can be attributed to the existence of a high velocity mafic intrusive rift pillow structure beneath the region probably emplaced during the rifting time this brittle competent high velocity zone beneath the epicentral area in response to the compression due to the northward movement of the indian plate could induce sufficient local stress perturbation for generating large intraplate earthquakes of m w 7 5 in the lower crust further within the overall higher velocity depth range a layer characterized by large values of v p 6 98 km s v s 3 854 km s and v p v s 1 81 is found in the depth range of 20 5 30 km which is inferred to be fractured and saturated high crack density and probably fluid filled presence of numerous fractures in this layer is confirmed by a high b value 0 75 1 1 in this layer this layer might have facilitated the nucleation process of the 2001 bhuj earthquake the major rupture and 47 of the aftershocks have occurred within this layer

regional tectonic framework structure and evolution of the western marginal basins of india abstract the kutch saurashtra cambay and narmada basins are pericontinental rift basins in the western margin of the indian craton these basins were formed by rifting along precambrian tectonic trends interplay of three major precambrian tectonic trends of western india dharwar nnw sse aravalli delhi ne sw and satpura ene wsw controlled the tectonic style of the basins the geological history of the basins indicates that these basins were formed by sequential reactivation of primordial faults the kutch basin opened up first in the early jurassic rifting was initiated in late triassic along the delhi trend followed by the cambay basin in the early cretaceous along the dharwar trend and the narmada basin in late cretaceous time along the satpura trend the evolution of the basins took place in four stages these stages are synchronous with the important events in the evolution of the indian sub continent its breakup from gondwanaland in the late triassic early jurassic its northward drifting during the jurassic cretaceous and collision with the asian continent in the early tertiary the most important tectonic events occurred in late cretaceous time the present style of the continental margins of india evolved during early tertiary time the saurashtra arch the extension of the aravalli range across the western continental shelf subsided along the eastern margin fault of the cambay basin during the early cretaceous it formed an extensive depositional platform continuous with the kutch shelf for the accumulation of thick deltaic sediments a part of the saurashtra arch was uplifted as a horst during the main tectonic phase in the late cretaceous the present high thermal regime of the cambay bombay high region is suggestive of a renewed rifting phase

multiple late holocene earthquakes along the reelfoot fault central new madrid seismic zone the reelfoot fault is an east vergent reverse fault underlying the lake county uplift a low amplitude late holocene anticline bordered on the east by the 32 km long reelfoot scarp fluvial deposits across the scarp define an 8 m high east facing monocline most near surface deformation along the scarp is accommodated via folding rather than faulting we interpret the scarp as a fault propagation fold developed over a wcst dipping reverse fault interpreted from shallow seismic reflection data trench exposurcs provide evidence for three episodes of deformation along the reelfoot fault within thc past approximately 2400 years between a d 780 and 1000 between a d 1260 and 1650 and during a d 1812 our best estimate of the average recurrence interval for deformation along the scarp is 400 500 years each episode of deformation had a slightly different style the third most recent event produced a small graben a few tens of centimeters deep in the hanging wall of the reverse fault the second most recent earthquake produced about 1 3 m of throw in the graben as well as folding along the updip projection of the reverse fault and development of the scarp thesc relations suggest that graben development increased through time concomitant with growth of the monocline or that the events are of different magnitude the 1811 1812 episode of deformation produced abundant liquefaction prominent folding of fluvial strata along the scarp and minor faulting in the graben

the tectonic evolution of western india and its impact on hydrocarbon occurrences an overview abstract the largest hydrocarbon accumulations of india were localized in western india by a unique convergence of tectonic events mesozoic rifting along the structural trends of proterozoic mobile belts formed the passive margin basins of the indian coast during the campanian rifting of madagascar from india north south striking normal faults propagated into the area of the cambay graben late maastrichtian doming over the incipient deccan reunion hotspot imparted extensional stresses to the northwestern indian coast and formed the fault block that became the bombay high after eruption of the deccan flood basalts in early paleocene extension continued in the weakened crust this resulted in enhanced subsidence of the cambay graben and surat danahu depression rifting of the seychelles microcontinent from india and reactivation of normal faults on the emergent bombay high the cambay graben and the surat danahu depression filled with organic rich source shales as they underwent thermal subsidence shallow water eocene to miocene carbonates developed on the slowly subsiding bombay platform and sea level oscillations fostered secondary porosity development late tertiary maturation of the surat danahu depression shales generated hydrocarbons that migrated into the carbonate reservoirs on the bombay high konkan kerala and the older basins of the east coast of india were unaffected by the post campanian tectonic events and lack the favorable play elements that characterize the giant fields

source parameters of the anjar earthquake of july 21 1956 india and its seismotectonic implications for the kutch rift basin abstract the kutch rift basin is a major seismic region in india characterized by a low earthquake occurrence rate but a very high maximum intensity the largest event in the region is the great kutch earthquake of 1819 estimated m w 7 8 however lacking instrumental data its exact source parameters are not well known the anjar or rann of kutch earthquake of july 21 1956 m w 6 0 took place very close to the 1819 kutch event and caused considerable damage and casualties our modeled waveforms of teleseismic p and sh waves and p wave first motions determine a reverse faulting mechanism strike 235 dip 46 5 and rake 85 as well as source parameters for the anjar earthquake a previous strike slip mechanism for this event has been eliminated on the basis of waveform constraints the two nodal planes of our solution both strike northeast sub parallel to the trend of the kutch rift very close to the trend of the isoseismals the seismic moment is 1 19 10 25 dyne cm the focal depth and the stress drop are 15 km and 162 bar respectively the anjar reverse fault may represent a reactivated normal fault undergoing tectonic inversion in the kutch rift zone under present day compressional stress two larger earthquakes adjacent to anjar but outside of the kutch rift are also found to be mainly reverse faulting with a minor strike slip component judging from available information the great kutch event of 1819 is most likely a reverse faulting event

paleoseismic evidence for recurrence of earthquakes near charleston south carolina a destructive earthquake that occurred in 1886 near charleston south carolina was associated with widespread liquefaction of shallow sand structures and their extravasation to the surface several seismically induced paleoliquefaction structures preserved within the shallow sediments in the meizoseismal area of the 1886 event were identified field evidence and radiocarbon dates suggest that at least two earthquakes of magnitudes greater than 6 2 preceded the 1886 event in the past 3000 to 3700 years the evidence yielded an initial estimate of about 1500 to 1800 years for the maximum recurrence of destructive intraplate earthquakes in the charleston region