preliminary observations from the 3 january 2017 m w 5 6 manu tripura india earthquake abstract on 3 january 2017 a m w 5 6 earthquake occurred in dhalai district in tripura india at 14 39 03 ist 09 09 03 utc with an epicentre at 24 018 n 4 9 km and 91 964 e 4 4 km and a focal depth of 31 6 0 km the focal mechanism solution determined after evaluating data from seismological observatories in india indicated a predominantly strike slip motion on a steeply dipping plane the estimated focal depth and focal mechanism solution places this earthquake in the indian plate that lies beneath the overlying indo burmese wedge as in the 2016 manipur earthquake a strong motion record from shillong india appears to suggest site amplification possibly due to topographic effects in the epicentral region in tripura damage assessed from a field survey and from media reports indicated that the macroseismic intensity approached 6 7 ems with damage also reported in adjacent parts of bangladesh a striking feature of this earthquake were the numerous reports of liquefaction that were forthcoming from fluvial locales in the epicentral region in tripura and at anomalous distances farther north in bangladesh the occurrence of the 2017 manu earthquake emphasises the hazard posed by intraplate earthquakes in tripura and in the neighbouring bengal basin region where records of past earthquakes are scanty or vague and where the presence of unconsolidated deltaic sediments and poor implementation of building codes pose a significant societal and economic threat during larger earthquakes in the future

sediment distribution circulation and provenance in a macrotidal bay garolim bay korea abstract a study of the sedimentary regime in garolim bay has been carried out in connection with a feasibility study for tidal power development at the mouth of the bay sand is shown to be circulating round a central bank between an ebb and a flood channel in the middle bay clay and heavy mineral distributions indicate a zone where finer sediments derived from offshore mix with those originating from the local streams quantities of land derived sediments are presumed to be deposited near the shores during the rainy summer season and these are redistributed during the windy winter season but the concentrations of suspended sediment are generally low the influx of sediment appears to largely balance the increase in sea level siltation over the general area may not be seriously increased after construction of a barrage but local siltation and scour near the barrage could be serious problems

stratigraphy of late quaternary deposits using high resolution seismic profile in the southeastern yellow sea abstract high resolution chirp and sparker system seismic profiles were analyzed to investigate the sequence stratigraphy of late quaternary deposits in the southeastern yellow sea approximately 1560 line km data of chirp and sparker profiles were acquired together with 11 piston cores two previous long drill cores ysdp 102 and 103 were used for comparison with seismic data high resolution seismic profiles image the holocene mud deposits and the complex sedimentary structure in this area sequence analysis of high resolution seismic profiles reveals that the shelf deposits form a succession of high frequency five order sequences consisting of one depositional sequence developed during the late quaternary the depositional sequence includes five sedimentary units each with different seismic facies and geometry 1 incised channel fill and lowstand deltaic wedge unit sy1 2 sand ridges unit sy2 3 estuarine deltaic mud unit sy3 4 redeposited mud unit sy4 and 5 recent distal mud unit sy5 based on the interpretation of high resolution seismic records and correlation with the ysdp 102 103 long cores and piston cores late quaternary deposits in the southeastern yellow sea consists of a set of the lowstand unit sy1 early transgressive unit sy2 middle transgressive unit sy3 late transgressive unit sy4 and highstand systems tract unit sy5 formed since the last glacial period the rather unusual stratigraphic architecture including three systems tracts is largely controlled by the postglacial sea level changes and regionally circulation pattern associated with sediment erosion and redeposition the results of this study present firstly clear seismic evidence that the southeastern yellow sea mud belt seysm can be divided into three stratigraphic units units sy3 sy4 and sy5 bounded by distinct bounding surfaces

convergence rate across the nepal himalaya and interseismic coupling on the main himalayan thrust implications for seismic hazard we document geodetic strain across the nepal himalaya using gps times series from 30 stations in nepal and southern tibet in addition to previously published campaign gps points and leveling data and determine the pattern of interseismic coupling on the main himalayan thrust fault mht the noise on the daily gps positions is modeled as a combination of white and colored noise in order to infer secular velocities at the stations with consistent uncertainties we then locate the pole of rotation of the indian plate in the itrf 2005 reference frame at longitude 1 34 3 31 latitude 51 4 0 3 with an angular velocity of 0 5029 0 0072 myr the pattern of coupling on the mht is computed on a fault dipping 10 to the north and whose strike roughly follows the arcuate shape of the himalaya the model indicates that the mht is locked from the surface to a distance of approximately 100 km down dip corresponding to a depth of 15 to 20 km in map view the transition zone between the locked portion of the mht and the portion which is creeping at the long term slip rate seems to be at the most a few tens of kilometers wide and coincides with the belt of midcrustal microseismicity underneath the himalaya according to a previous study based on thermokinematic modeling of thermochronological and thermobarometric data this transition seems to happen in a zone where the temperature reaches 350 c the convergence between india and south tibet proceeds at a rate of 17 8 0 5 mm yr in central and eastern nepal and 20 5 1 mm yr in western nepal the moment deficit due to locking of the mht in the interseismic period accrues at a rate of 6 6 0 4 10 19 nm yr on the mht underneath nepal for comparison the moment released by the seismicity over the past 500 years including 14 m w 7 earthquakes with moment magnitudes up to 8 5 amounts to only 0 9 10 19 nm yr indicating a large deficit of seismic slip over that period or very infrequent large slow slip events no large slow slip event has been observed however over the 20 years covered by geodetic measurements in the nepal himalaya we discuss the magnitude and return period of m 8 earthquakes required to balance the long term slip budget on the mht

late quaternary stratigraphy and development of tidal sand ridges in the eastern yellow sea abstract the eastern yellow sea is characterized by a number of tidal sand ridges which occur as a series of linear sediment bodies in the shelf shelf sand ridges and as a group of individual sand bodies in the nearshore nearshore sand ridges the shelf sand ridges are present in water depths of 50 90 m and show large elongate shapes with a length up to 200 km in contrast the nearshore sand ridges are much smaller in size up to 34 km length and occur in water depths shallower than about 30 m detailed interpretation of seismic and lithologic data using radiocarbon dating to constrain the ages of the ridges has shown that the regional sea level changes played a major role in the existence and development of different morphologic features of these sand ridges the shelf sand ridges developed mainly during the postglacial transgression ca 14 000 9 500 yr b p possibly during episodes of stillstand or very slow rise of sea level the shape of the shelf sand ridges more or less results from an erosional process dominantly acting during the postglacial transgression the substratum of the shelf sand ridges consists of the regressive or lowstand deltaic mud deposits probably formed prior to the last glacial maximum ca 17 000 yr b p in contrast the nearshore sand ridges have undergone tidal action during the recent highstand of sea level ca 7 000 yr b p and show a typical modern geomorphology of erosional sand ridges the substratum of the nearshore sand ridges consists of remnants of the last interglacial tidal deposits large dunes indicate a strong hydrodynamic influence on the entire ridge surface at present

partitioning of transgressive deposits in the southeastern yellow sea a sequence stratigraphic interpretation abstract the last glacio eustatic sea level fluctuation in the southeastern part of the yellow sea formed a number of unconformity bounded sedimentary sequences these sequences comprise 1 regressive to transgressive incision fills unit c 2 transgressive sand ridges and swales unit b and 3 transgressive to highstand muds lower mud unit a2 upper mud unit a1 the sequence boundary between unit c and the lower unit comprises erosional surface which can be traced for the entire study area the even and sharp boundary between the incision fills unit c and the sand ridges unit b represents a transgressive surface of erosion the depositional boundary between the lower mud unit a2 and the upper mud unit a1 suggests a change in oceanographic conditions the boundary is confined landward and correlated offshore with the top of units b and c that is exposed on the seafloor these transgressive deposits show partitioning controlled by currents tides and sediment supply as well as physiography of the seafloor

stratigraphy structure and tectonic evolution of the himalayan fold thrust belt in western nepal regional mapping stratigraphic study and 40ar 39ar geochronology provide the basis for an incremental restoration of the himalayan fold thrust belt in western nepal tectonostratigraphic zonation developed in other regions of the himalaya is applicable with minor modifications in western nepal from south to north the major structural features are 1 the main frontal thrust system comprising the main frontal thrust and two to three thrust sheets of neogene foreland basin deposits 2 the main boundary thrust sheet which consists of proterozoic to early miocene lesser himalayan metasedimentary rocks 3 the ramgarh thrust sheet composed of paleoproterozoic low grade metasedimentary rocks 4 the dadeldhura thrust sheet which consists of medium grade metamorphic rocks cambrian ordovician granite and granitic mylonite and early paleozoic tethyan rocks 5 the lesser himalayan duplex which is a large composite antiformal stack and hinterland dipping duplex and 6 the main central thrust zone a broad ductile shear zone the major structures formed in a general southward progression beginning with the main central thrust in late early miocene time eocene oligocene thrusting in the tibetan himalaya north of the study area is inferred from the detrital unroofing record on the basis of 40ar 39ar cooling ages and provenance data from synorogenic sediments emplacement of the dadeldhura thrust sheet took place in early miocene time the ramgarh thrust sheet was emplaced between 15 and 10 ma the lesser himalayan duplex began to grow by 10 ma simultaneously folding the north limb of the dadeldhura synform the main boundary thrust became active in latest miocene pliocene time transport of its hanging wall rocks over an 8 km high footwall ramp folded the south limb of the dadeldhura synform thrusts in the subhimalayan zone became active in pliocene time the minimum total shortening in this portion of the himalayan fold thrust belt since early miocene time excluding the tibetan zone is 418 493 km the variation depending on the actual amounts of shortening accommodated by the main central and dadeldhura thrusts the rate of shortening ranges between 19 and 22 mm yr for this period of time when previous estimates of shortening in the tibetan himalaya are included the minimum total amount of shortening in the foldthrust belt amounts to 628 667 km this estimate neglects shortening accommodated by small scale structures and internal strain and is therefore likely to fall significantly below the actual amount of total shortening

holocene development of the yellow river s subaqueous delta north yellow sea high resolution seismic profiles from the north yellow sea reveal a 20 40 m thick subaqueous clinoform delta that wraps around the eastern end of the shandong peninsula extending into the south yellow sea this complex sigmoidal oblique clinoform containing an estimated 400 km 3 of sediment overlies prominent relict transgressive surfaces the nearshore topset of the clinoform 50 m contain less than 1 m of holocene sediment with low sedimentation rates 1 mm year in contrast to other clinoforms the shandong clinoform appears to be a compound subaqueous deltaic system with what we interpret to be proximal and distal phases of clinoform development the underlying proximal sequence formed proximally between f11 and 9 2 ka in response to a temporary pause in the rapid postglacial sea level rise after the meltwater pulse 1b mwp 1b and increased discharge from the yellow river to the north yellow sea due to intensification of the summer monsoon a flooding surface appears to separate the proximal and distal phases corresponding to the next rapid sea level rise 9 5 9 2 ka bp mwp 1c since 9 2 ka bp an overlying distal sedimentary sequence has accumulated reflecting the backstepping and shifting river mouth westward to the gulf of bohai some inputs from coastal erosion and nearby small streams may be locally important along shore transport cross shelf advection and upwelling in the north yellow sea have reworked post lgm sediment and have helped maintain the morphology of the clinoform in the shandong mud wedge d 2004 elsevier b v all rights reserved

attenuation of intensities and effect of local site conditions on observed intensities during the corinth greece earthquakes of 24 and 25 february and 4 march 1981 abstract field investigations conducted immediately after the gulf of corinth earthquake of 24 february 1981 provide an extensive set of data on intensity at different sites for the main shock and two of its principal aftershocks each site of intensity observation was characterized by the local site geologic condition the hypocenters of the three shocks were relocated by using the joint epicenter location technique with the aftershock of 12 march 1981 01 49 utc recorded by six portable stations as well as stations of the greek national seismographic network as the calibration event isoseismal maps prepared by using all intensity data for the three shocks were used to derive new attenuation relations analysis of the intensity residuals observed calculated intensity shows that local site geologic condition has a significant effect on the intensity observed at a site on an average under similar circumstances sites located on soil foundations experience about one intensity unit more shaking than sites located on rock foundations likewise sites located on neogene sediments intermediate foundation condition experience about 1 2 unit greater intensity effect than sites located on rock foundations attenuation relations derived by using intensity data for the three february march 1981 earthquakes show lower attenuation than the relation derived by using published isoseismal maps for 19 earthquakes which occurred in the corinth saronikos region during 1861 to 1975

southern ocean contributions to glacial interglacial changes of atmospheric pco2 an assessment of carbon isotope records in diatoms eleven new antarctic records of diatom bound 13corg show significantly lighter values during the last glacial maximum than during the holocene with a general trend of increasing depletions southward of the modern antarctic polar front mapf in contrast glacial diatoms from cores farther north of the mapf show 13corg values which are 1 heavier than during the holocene likely causes for the low glacial 13corg in antarctic diatoms are higher co2 aq lower growth rates and changes in diatom abundance or size taken at face value the glacial depletions of 13corg suggest that antarctic surface waters south of the mapf might have been a source of atmospheric pco2 during the glacial period alternatively the glacial depletions might have been caused by either a relatively small decrease in growth rates or changes in the abundance of the two dominant diatom species or their average cell size interpretations of the subantarctic records are complicated by similar uncertainties

sedimentology of a subtidal tide dominated sand body in the yellow sea southwest korea abstract odanam satoe a subtidal tide dominated sand body in the yellow sea korea is linear in plan and asymmetrical in cross section it consists of fine to medium grained well sorted subangular sand bedforms consist of high amplitude 1 2 m sandwaves on the lower flanks of the gentler sloping bar surface and medium amplitude 0 5 1 m sandwaves on the sand body trough adjoining the steeper face the bar crest and shallower parts of the gently sloping bar surface bedforms are absent on the relatively steeper bar surface which is characterized by 2 slopes bedform orientation on the gentler slope is oblique by 30 to the bar crest parallel to the sand body crest on the crest itself and opposite to the steeper sand body face in the trough below the steeper slope of the bar bottom current velocity data show that tidal currents are semi rotary with a flood time velocity asymmetry over the gentler slope and ebb time velocity asymmetry over the steeper slope during most of the tidal cycle tidal current flow parallels bar elongation over the steeper slope whereas over the gentler slope tidal current flow is directed at 30 to the bar crest and changes to normal to the crest one hour prior to low tide bedform orientation mapped with side scan sonar shows agreement with these flow directions sand dispersal around the sand body is controlled by time velocity asymmetry and partial rotary flow directions of tidal currents this circulation causes not only a trapezoidal mode of grain dispersal but also westerly migration of the sand body documented from comparative bathymetric surveys in 1964 and 1980

seismological geodetic macroseismic and historical context of the 2016 mw 6 7 tamenglong manipur india earthquake abstract the 2016 mw 6 7 tamenglong earthquake in the state of manipur in northeastern india on 4 january 2016 at 04 35 indian standard time 3 january 23 05 utc was the strongest earthquake to strike manipur since 1988 using data from indian stations we constrain the hypocentral depth of the mainshock at 59 3 8 km and determine a strike slip mechanism with a moderate reverse component on a steeply dipping plane though coseismic offsets from gps measurements from four nearby sites were inadequate to provide further constraints on the focal mechanism they were consistent with the magnitude and hypocentral depth of the earthquake the epicentre of the mainshock was located 15 km west of the churachandpur mao fault cmf but it was unrelated to this structure and was instead a typical intra slab earthquake within the indian plate a strong motion instrument at the loktak power station lok 56 km from the epicentre recorded a peak ground acceleration pga of 0 027g while a pga of 0 103g was recorded at shillong shl at an epicentral distance of 111 km we also present macroseismic observations from 461 locations in north eastern india and the adjacent areas for this earthquake the highest intensities 7 ems were observed in the manipur valley and in the hills to the west while shaking was perceptible as far as delhi and jaipur lastly we present a catalogue of 333 felt earthquakes in manipur from 1588 1 ce to 1955 derived from the royal chronicle of the kings of manipur known as the cheitharon kumpapa discuss important historical earthquakes in the region and also estimate intensity magnitudes for the 1852 mi 6 5 0 8 1869 mi 7 1 0 7 1880 mi 6 3 0 7 and 2016 mi 6 8 0 8 earthquakes

attenuation of intensity for the 1887 northern sonora mexico earthquake abstract contouring the intensity data for the northern sonora earthquake of 1887 yields an area of perceptibility defined by the mm iii isoseismal that is greatly elongated to the southeast of the epicenter along the sierra madre occidental north of the epicenter the isoseismals are compressed due to the change in crustal structure between the colorado plateau and the southern basin and range province the higher intensity isoseismals are more symmetric although local structure strongly influences individual intensity values to evaluate the attenuation of intensity with distance three regression curves are calculated as below all data i 12 0 3 2 0 0015 r 1 5 in r 25 500 km i 12 0 0 69 0 0069 r 0 82 in r isoseismal i 12 0 8 1 0 0031 r 2 3 in r where r is the epicentral distance in kilometers the all data curve is derived from a regression computed using all 171 intensity values the 25 500 km curve eliminates the near and far points and the isoseismal curve is a regression on the average radii of the area enclosed by each isoseismal contour the latter two curves are similar to curves for the western united states as a whole anderson 1978 or the cordilleran curve of howell and schultz 1975 for intensities less than or equal to mm x the curve for all data indicates less attenuation at lower isoseismals than the other two 1887 regressions and falls between the cordilleran and eastern united states models of howell and schultz

distribution of suspended sediment in the korea strait and southeastern yellow sea onset of winter monsoons abstract high energy conditions in the yellow sea begin each year with the onset of monsoon winds in late october these transitional season surges of cold air initiate sediment resuspension vertical mixing of suspended sediments and a wind driven coastal current that flows to the south during the summer to winter transition suspended sediment concentrations in the southeastern yellow sea range from 5 100 mg l 1 at the surface and 5 500 mg l 1 at the bottom the highest concentrations occur off the southwest tip of the korean peninsula and the lowest occur in the central part of the korea strait the rate of transitional season destratification may depend on the timing and intensity of monsoonal surges whereas a late onset of monsoon winds allows waters to remain longer in their moderately stratified summer condition an early onset of monsoon winds tends to destratify the water column by mid november resulting in a nearly uniform high concentration of suspended sediments from surface to bottom the band of more turbid coastal water ends abruptly 25 50 km offshore as a turbidity front in waters 20 80 m deep a wind driven residual flow to the south appears to transport large volumes of this turbid water into the korea strait and perhaps as far as the sea of japan

a seismic hazard map of india and adjacent areas abstract we have produced a probabilistic seismic hazard map showing peak ground accelerations in rock for india and neighboring areas having a 10 probability of being exceeded in 50 years seismogenic zones were identified on the basis of historical seismicity seismotectonics and geology of the region procedures for reducing the incompleteness of earthquake catalogs were followed before estimating recurrence parameters an eastern united states acceleration attenuation relationship was employed after it was found that intensity attenuation for the indian region and the eastern united states was similar the largest probabilistic accelerations are obtained in the seismotectonic belts of kirthar hindukush himalaya arakan yoma and the shillong massif where values of over 70 g have been calculated

phase relationships between millennial scale events 64 000 24 000 years ago a core recovered on the iberian margin off southern portugal can be correlated with greenland ice cores using oxygen isotope variability in planktonic foraminifera which closely matches the ice core records of temperature over greenland our age model identifies the base of every interstadial between 64 000 and 24 000 years ago and uses the greenland ice core project grip timescale the oxygen isotope signal in benthic foraminifera on this grip based timescale is quite different from the planktonic record and resembles the temperature record over antarctica when this is synchronized with greenland using the record of methane in the atmospheric air in the polar ice cores we interpret the benthic record as indicating significant fluctuations in ice volume during millennial events and we suggest that antarctic temperature changed as a function of ice volume

late quaternary seismic stratigraphy in response to postglacial sea level rise at the mid eastern yellow sea late quaternary seismic stratigraphy and depositional history at the mid eastern yellow sea were investigated using high resolution seismic profiles and core sediments the results show that the shelf sequence consists of five sedimentary units formed since the lgm incised channel fill su1 estuarine deposit su2 thin sand veneer su3 tidal sand ridge su4 and central deltaic mud su5 the lowermost unit su1 above the sequence boundary is interpreted as channel fill deposits mainly formed during the lgm which belongs to the lowstand systems tract three units su2 su3 and su4 regarded as transgressive systems tract can be grouped into paralic and marine components separated by a ravinement surface su2 lying below the ravinement surface represents a paralic unit that consists of estuarine sediments left behind from shoreface erosion the top surface of su2 is truncated by an erosional surface and is overlain by two marine units su3 and su4 which were produced by shoreface erosion that shifted landward during the transgression su3 mainly distributed over a wide area of the central part is very thin whereas su4 on the eastern part off the korean peninsula forms serial sand ridges partly modified by modern tidal currents the uppermost unit su5 above the maximum flooding surface regarded as the highstand systems tract formed the thin deltaic mud patch derived from the huanghe river developed after the highstand sea level approximately 7 ka bp

post earthquake aggradation processes to hide surface ruptures in thrust systems the m8 3 1934 bihar nepal earthquake ruptures at charnath khola eastern nepal the charnath khola is a large river crossing the himalayan thrust system in the region devastated by the great m8 3 1934 bihar nepal earthquake fluvial terraces are abandoned along the river and at the base of a 20 m high cumulative thrust escarpment a trench across the fault scarp exposed siwalik mudstone siltstone overthrusting quaternary units and three colluvial wedges interfingered with fluvial sands the 85 accelerator mass spectrometry radiocarbon dates from detrital charcoals sampled in the trench a river cut and river terraces constrain the timing of the sedimentary processes following the last two major earthquakes in 1934 and 1255 ce although several samples straddle the main earthquake horizon associating it with the 1934 earthquake based solely on radiocarbon ages remains challenging the 49 detrital charcoal ages found in the pre earthquake and postearthquake units fall between 65 and 225 bp a period with a flat calibration curve many of these radiocarbon ages are suspected to include a part due to inbuilt time i e age of the wood at the time of burning transport time and reworking processes which are difficult to resolve considering these ages at their face value could lead to dates older than the actual earthquake dates we suggest that a part of this chronological bias is also related to a local postseismic aggradation pulse of 4 to 5 m of sediments which is documented in the trench and terraces this fluvial sequence hiding the most recent surface rupture is likely related to landslide sediment deposition triggered by the 1934 bihar nepal earthquake

pleistocene forced regressions and tidal sand ridges in the east china sea abstract tidal sand ridges are common features on modern shelves but only few examples of such preserved sand bodies are described in pleistocene deposits in the stratigraphic record some sand bodies encased in shales previously interpreted as sand ridges have been reinterpreted as shoreface deposits more than 5000 km of high resolution seismic data from the east china sea correlated to geotechnical boreholes and shallow cores demonstrate the potential of sand ridge preservation and allow reconstruction of the depositional history of pleistocene fourth order 100 kyr depositional sequences a high subsidence rate of about 300 m myr allows the preservation of three elementary sedimentary facies constitutive of a motif which was repeated during glacio eustatic cycles they consist of 1 regressive marine prodeltaic prograding wedges 2 estuarine and continental deltaic facies and 3 transgressive sand ridges similar in shape and orientation to modern sand ridges major discontinuities traceable over the entire outer continental shelf along distances of hundreds of kilometers are transgressive and regressive surfaces of marine erosion whereas sequence boundaries formed by fluvial erosion are difficult to identify on this low gradient shelf because of the asymmetry of the pleistocene glacio eustatic cycles most of the preserved sedimentary record with the exception of sand ridges corresponds to forced regressive deposits deposits that formed during a seaward shift of the shoreline due to relative sea level lowering

the shallow marine architecture knowledge store a database for the characterization of shallow marine and paralic depositional systems abstract the shallow marine architecture knowledge store smaks is a relational database devised for the storage of hard and soft data on the sedimentary architecture of ancient shallow marine and paralic siliciclastic successions and on the geomorphological organization of corresponding modern environments the database allows incorporation of data from the published literature which are uploaded to a common standard to ensure consistency in data definition the database incorporates data on geological entities of varied nature and scale i e surfaces depositional tracts architectural elements sequence stratigraphic units facies units geomorphic elements including attributes that characterize their type geometry spatial relations hierarchical relations and temporal significance furthermore geological entities are assigned to depositional systems or to parts thereof that can be classified on multiple parameters e g shelf width delta catchment area tied to metadata e g data types data sources the smaks permits the quantitative characterization of modern and ancient shallow marine and paralic clastic depositional systems it aims to serve as a repository of analogue information for hydrocarbon bearing successions and as a research tool that can be applied to aid the development of facies models or to assess the sensitivity of depositional systems to particular controlling factors for example to demonstrate the wide applicability of the database in fields of both fundamental and applied research example database output is presented that i includes data from wave tide and fluvial dominated shallow seas and sedimentary successions and ii covers a wide depositional spectrum from backshore to shelf edge settings the examples include information on the facies organization of different types of paralic sub environments on the hierarchical arrangement of architectural elements that form deltaic constructional units in quaternary deltas on the morphometry of modern and quaternary tidal sand ridges and on the geometry of parasequence scale nearshore sandstone belts from the upper cretaceous of the western interior seaway in utah usa

transgressive sand ridges on the mid shelf of the southern sea of korea korea strait formation and development in high energy environments abstract the mid shelf of the southern sea of korea korea strait is covered by a series of shore parallel sand ridges up to 63 km long 3 9 km wide and 22 m thick the ridges are a moribund type but show well organized dipping strata indicating appreciable progradation the submerged paleo channel system the paleo seomjin river associated with the sand ridge field suggests that the ridges primarily originated from river mouth sandy shoals which subsequently developed into shore parallel linear sand bodies in high energy environments the combined effect of coastal tidal and longshore and offshore ocean currents was possibly responsible for shore parallel sediment transport and growth of the ridges 14c dates core lithology and sea level data suggest that the sand ridges mainly formed and developed during the middle period of the postglacial transgression they are postulated to have developed sequentially from offshore to onshore in response to sea level rise during that time very slow sea level rise and high sediment supply through the paleo channel system probably provided favorable conditions for forming the sand ridges the ridges became inactive during the late transgression period as a result of a substantial reduction of wave and current strength and remained on the mid shelf

seismology raising kathmandu on 25 april 2015 northern nepal shifted up to 7 m southward and kathmandu was raised by 1 m the causal earthquake failed to fully rupture the main fault beneath the himalaya and hence a large earthquake appears to be inevitable in nepal s future

seismic stratigraphy and depositional history of late quaternary deposits in a tide dominated setting an example from the eastern yellow sea abstract analysis of high resolution seismic profiles and sediment data from the eastern yellow sea reveals that the late quaternary deposits comprise six seismic units interpreted as transgressive and highstand systems tracts formed since the lgm each unit was deposited during distinctive portions of the sea level curve associated with hydrodynamic conditions during the lgm 19 ka bp the study area was completely exposed resulting in subaerial erosion associated with paleo channel incision by the huanghe and korean rivers as the shelf was flooded the incised channels were backfilled fluvial or coastal sediments forming incised channel fill deposits su1 the paleo river may have supplied abundant terrigenous sediments to the study area around the paleo river mouth and adjacent area these sediments were trapped within the paleo estuary and formed su2 regarded as an estuarine deposit two types of serial sand ridges su3 and su5 which correspond to transgressive deposits developed su3 on the southern part west of jeju island 80 110 m deep is regarded as a moribund type mainly formed during the early to middle stage of transgression these are thought to have ceased growing and remobilizing in contrast su5 occurring 30 50 m deep off the korean peninsula is generally regarded as active sand ridges deposited during the late stage of transgression and is partly modified by modern tidal currents as the transgression continued the near surface sediments were reworked and redistributed by shelf erosion resulting in a thin veneer of transgressive sands su4 the uppermost unit su6 formed the heuksan mud belt hmb which is one of the most prominent mud deposits in the yellow sea the lower part of the hmd corresponds to shelf mud deposited during the late stage of transgression whereas the upper part consists of a recent shelf delta developed after the highstand sea level at about 7 ka bp

seismotectonics of the nepal himalaya from a local seismic network the national seismological network of nepal consists of 17 short period seismic stations operated since 1994 it provides an exceptional view of the microseismic activity over nearly one third of the himalayan arc including the only segment between longitudes 78 e and 85 e that has not produced any m 8 earthquakes over the last century it shows a belt of seismicity that follows approximately the front of the higher himalaya with most of the seismic moment being released at depths between 10 and 20 km this belt of seismicity is interpreted to reflect interseismic stress accumulation in the upper crust associated with creep in the lower crust beneath the higher himalaya the seismic activity is more intense around 82 e in far western nepal and around 87 e in eastern nepal western nepal between 82 5 and 85 e is characterized by a particularly low level of seismic activity we propose that these lateral variations are related to segmentation of the main himalayan thrust fault the major junctions between the different segments would thus lie at about 87 e and 82 e with possibly an intermediate one at about 85 e these junctions seem to coincide with some of the active normal faults in southern tibet lateral variation of seismic activity is also found to correlate with lateral variations of geological structures suggesting that segmentation is a long lived feature we infer four 250 400 km long segments that could produce earthquakes comparable to the m 8 4 bihar nepal earthquake that struck eastern nepal in 1934 assuming the model of the characteristic earthquake the recurrence interval between two such earthquakes on a given segment is between 130 and 260 years

temporal significance of sequence boundaries abstract this paper analyses the temporal significance of stratigraphic surfaces bounding the marine portions of the depositional sequence genetic stratigraphic sequence and transgressive regressive sequence these bounding surfaces known as the correlative conformity c c maximum flooding surface mfs and conformable transgressive surface cts respectively may either be defined on the basis of stratal stacking patterns which we call type a surfaces or on the basis of water depth changes and relative sea level changes which we call type b surfaces the type a mfs and cts are time lines in a depositional dip section corresponding to the turnaround points from shoreline transgression to regression and vice versa they separate prograding coarsening upward from retrograding fining upward geometries with a timing determined by the interplay between the rates of sedimentation and relative sea level rise in the shoreline area the timing of type a mfs and cts is not affected by the offshore variations in sedimentation and subsidence rates but it is only controlled by the shoreline movements and the associated facies shifts the type a c c separates rapidly prograding and offlapping forced regressive strata from the overlying lower rate prograding and aggrading normal regressive strata this surface is diachronous younger basinward with the rate of offshore sediment transport the timing of the type a c c in the shoreline area corresponds to the end of relative sea level fall but it develops under relative sea level rise conditions offshore the timing of the type b mfs and cts depends on the offshore variations in the sedimentation and subsidence rates these surfaces defined on the basis of bathymetric changes become younger and older seaward respectively tending to merge together offshore the type b c c marks the end of relative sea level fall in any point along a depositional dip section it is diachronous older basinward as its timing depends on the offshore variations in subsidence rates the diachroneity of type b surfaces reaches a quarter of the period of the highest frequency variable whichever that is among the eustasy tectonics or sedimentation controls types a and b surfaces merge together in the shoreline area but they become temporally divergent offshore deepening upward and shallowing upward facies should not be confused with transgressive and regressive systems tracts the latter are strictly controlled by the shoreline movements which determine the direction of facies shifts and the stratal stacking patterns

intensity magnitude location and attenuation in india for felt earthquakes since 1762 a comprehensive consistently interpreted new catalog of felt intensities for india martin and szeliga 2010 this issue includes intensities for 570 earth quakes instrumental magnitudes and locations are available for 100 of these events we use the intensity values for 29 of the instrumentally recorded events to develop new intensity versus attenuation relations for the indian subcontinent and the himalayan region we then use these relations to determine the locations and mag nitudes of 234 historical events using the method of bakun and wentworth 1997 for the remaining 336 events intensity distributions are too sparse to determine mag nitude or location we evaluate magnitude and location accuracy of newly located events by comparing the instrumental with the intensity derived location for 29 cali bration events for which more than 15 intensity observations are available with few exceptions most intensity derived locations lie within a fault length of the instrumen tally determined location for events in which the azimuthal distribution of intensities is limited we conclude that the formal error bounds from the regression of bakun and wentworth 1997 do not reflect the true uncertainties we also find that the regression underestimates the uncertainties of the location and magnitude of the 1819 allah bund earthquake for which a location has been inferred from mapped surface deformation comparing our inferred attenuation relations to those developed for other regions we find that attenuation for himalayan events is comparable to intensity attenuation in california bakun and wentworth 1997 while intensity attenuation for cratonic events is higher than intensity attenuation reported for central eastern north america bakun et al 2003 further we present evidence that intensities of intraplate earth quakes have a nonlinear dependence on magnitude such that attenuation relations based largely on small to moderate earthquakes may significantly overestimate the magnitudes of historical earthquakes

the status of central seismic gap a perspective based on the spatial and temporal aspects of the large himalayan earthquakes abstract the central himalaya considered as a prominent seismic gap is generally believed to be the most vulnerable segment due for a great plate boundary earthquake m 8 two significant historical earthquakes are known to have occurred in this region in ad 1505 and 1803 interpreted by some workers as great earthquakes occurrences of these events question the validity of central himalaya being a seismic gap here we analyze the macroseismal data from the central himalaya and the gangetic plains and suggest that neither of these earthquakes can be qualified as a plate boundary type event and the size of at least the 1803 does not exceed mw 7 7 our studies further indicate that the central himalayan frontal thrusts may be undergoing a quiescence of 1000 years in terms of generation of great earthquakes assuming a steady elastic strain accumulation due to plate convergence and its simple translation as periodic great earthquakes such long quiescence may appear intriguing we suggest that the long term quiescence and the spatial and temporal clustering that characterize the distribution of large earthquakes in the himalaya is a manifestation of the tectonic deformation associated with a highly evolved fold and thrust belt our analyses also indicate that the large moderate earthquakes are mostly concentrated on higher level thrusts these structures probably accommodate most of the seismogenic slip in the himalaya and the rest of the strain could possibly be expended on passive folding consequently great earthquakes m 8 are relatively infrequent as in the case of central himalaya apparently leading to long periods of quiescence

formation of the yangtze shoal in response to the post glacial transgression of the paleo yangtze changjiang estuary china abstract the yangtze shoal lies east of the yangtze changjiang river estuary china at water depths of 25 55 m and is one of the largest subaqueous sheet like sand banks in the world previous studies have not reached a consensus regarding its origin and timing of formation mainly due to the scarcity of coring and high resolution seismic profiling in the shoal we recovered a 70 20 m long sediment core cre 1402 through the sand shoal and acquired 1586 km of high resolution shallow seismic profiles across the estuary and shoal we conducted systematic analyses of the core including its sedimentary characteristics down core changes in benthic foraminiferal assemblages and 14c and optically stimulated luminescence osl dating we also analyzed the seismic stratigraphy and integrated these results with data from other previously well studied cores onshore and offshore of the yangtze river mouth our results indicate that the stratigraphic architecture in the paleo yangtze estuary i e the area from the present day delta plain to the subaqueous delta and yangtze shoal was controlled mainly by changes in sea level during the post glacial transgression the post 14 ka sedimentary successions in the paleo estuary rest unconformably on fluvial or coastal deposits that formed mainly before mis 1 and are separated by three distinctive bounding surfaces corresponding to mwp 1a mwp 1b or the rapid sea level rise at ca 11 5 ka shortly after the younger dryas cold period and the 8 2 ka event respectively and the maximum marine flooding surface mfs the depositional unit of the yangtze shoal ranges in thickness from 6 to 32 m the shoal exhibits large scale sw dipping generally 0 5 2 foresets with local cross cutting of foresets which are composed mainly of very fine to medium grained sands the shoal is underlain by muddy intertidal to subtidal flat deposits that formed during the younger dryas with an erosional surface corresponding to mwp 1b or the rapid sea level rise at ca 11 5 ka between these and the shoal deposits the yangtze shoal came into being mainly between ca 11 5 and 7 0 ka in the form of tidal sand ridges actively moving southwestwards under intense and reciprocal tidal currents on a tidal shelf the tidal sand ridges have evolved into sheet like tidal sand banks with relatively low relief as a result of tidal remobilization under rotary tidal currents since ca 7 0 ka when the mfs formed therefore the yangtze shoal can be considered to comprise quasi active tidal sand banks

observations on shelf and subtidal channel flow implications of sediment dispersal seaward of the keum river estuary korea although much of the fine grained sediment in the south eastern yellow sea is attributed to discharge from the keum river dispersal of these sediments by tide or wind has never been determined by direct current measurements in this paper we provide in situ observations of currents in two dispersal systems immediately seaward of the keum river entrance one of these is a subtidal channel system that defines flow from the shallow subtidal region seaward to the shelf and the other is the inner shelf mudstream where mixing is maintained primarily by tides subtidal channels have moderate current speeds but low suspended sediment concentrations instantaneous current speeds during spring tide were of the order 100 cm s 1 and suspended sediment concentrations were typically less than 10 mg l 1 at the surface and 40 mg l 1 at the bottom under fair weather conditions subtidal channels play a negligible role in offshore sediment dispersal since sediment concentrations during flood appear to equal or exceed those during ebb instantaneous currents at two stations on the shelf were of the same order as those in subtidal channels but displayed net flow to the south at speeds of 7 8 and 3 8 cm s 1 we speculate that subtidal channels provide the conduits for transporting sediments directly offshore during winter monsoons on an annual time scale one model for sedimentation would be low sediment influx from rivers but high influx from tidal flats to the coast during winter when north winds generate large waves in the yellow sea and the reverse in summer when winds from the south produce little wave activity coastal muds would thus be eroded in winter and replenished by high river discharge in summer further it is reasonable to assume that residual flow to the south would strengthen in winter as the monsoon season progressed thus the introduction of resuspended tidal flat sediments would coincide with the best developed dispersal system

stratigraphy and subaerial exposure of late quaternary tidal deposits in haenam bay korea south eastern yellow sea late quaternary stratigraphy of the coastal deposits in haenam bay south western coast of korea south eastern yellow sea consists of two depositional units a holocene intertidal deposit unit i and an underlying late pleistocene tidal deposit unit ii both of which are distinguished by distinct unconformity the yellowish colour and more consolidated and oxidized nature are characteristics of the sediments in the upper part of unit ii in spite of the lack of primary sedimentary structures a conspicuous cryogenic structure was found in the upper part of unit ii reflecting cold and dry conditions the magnetic susceptibility enhancement in the upper part of unit ii added the possibility of pedogenesis during subaerial exposure the upper part of unit ii is characterized by the deficiency of smectite and chlorite in contrast to the clay mineral suites of unit i and lower part of unit ii which may be attributed to post depositional and diagenetic alteration the degree of weathering measured by the chemical index of alteration shows that the removal of labile minerals by leaching also occurred in the upper part of unit ii thus the upper part of this unit appears to have undergone subaerial exposure and weathering during low sea level stands the supporting evidence of the sediment properties including sediment colour and structure water contents and shear strength geochemical and clay mineralogical data and magnetic susceptibility provides the potential signature of the subaerial exposure and weathering of late pleistocene sediments in the tidal dominated haenam bay sedimentary basin

upper crustal compressional wave velocity in the garhwal himalaya a value of 5 2 km s is obtained for compressional wave velocity in the upper crust in the vicinity of the main central thrust where it crosses the yamuna and bhagirathi valleys in the garhwal himalaya the data used consisted of the arrival times of compressional waves recorded at five portable stations from nine earthquakes occurring in the region

oblique convergence in the himalayas of western nepal deduced from preliminary results of gps measurements a gps network consisting of 29 sites was installed in central and western nepal with measurements taken in 1995 and partial remeasurements in 1997 data suggest 15 5 mm yr of n180 convergence between the higher himalayas and india a result that is consistent with n s shortening across the arcuate shape of the nepalese himalayas and an oblique underthrusting of the indian crust below the high himalayas of western nepal a 4 3 mm year e w extension and deviation of the principal shortening axes are inferred east of 83 e where quaternary faults darma bari gad fault system and thakkhola graben delineate a crustal wedge this wedge is located on the se projection of the karakorum fault and may segment the himalayan thrust belt the convergence between the outer belt of western nepal and india is less than 3 mm yr an attenuation consistent with creep on a dislocation locked beneath the lesser himalayas a preliminary model suggests that this n 120 e striking dislocation is affected by a 19 mm yr thrust component and a 7 mm yr right lateral component

evolution of late quaternary mud deposits and recent sediment budget in the southeastern yellow sea abstract analysis of high resolution seismic reflection profiles and sediment samples has revealed the evolution and sediment budget of the southeastern yellow sea mud belt seysm along the southwestern korean peninsula the seysm up to 50 m thick over 250 km long and 20 55 km wide can be divided into three stratigraphic units a1 a2 and b from oldest to youngest unit a1 overlying the acoustic basement comprises the northern part of the seysm unit a2 comprises the southern part of the seysm much of unit a2 is exposed at the seafloor unit b completely covers unit a1 and pinches out southward 14c data suggest that evolution of each unit is closely related to the postglacial sea level changes unit a1 consists of estuarine deltaic or shallow water muds deposited during the early to middle stage of postglacial sea level rise ca 14 000 7000 yr b p unit a2 corresponds to relict muds deposited during the last deceleration stage of sea level rise ca 7000 3 500 yr b p unit b consists of shelf muds deposited during the recent sea level highstand ca very low background activities of 210pb of the surface sediment of unit a2 suggest that the present day sediment accumulation is negligible in the southern seysm on the other hand 210pb excess activity profiles in unit b yield an average sediment accumulation rate of 3 9 mm yr indicating active sediment accumulation in the northern seysm the annual sink 3 0 10 7 tons yr of fine grained sediment in unit b is about an order of magnitude greater than can be explained by the sediment input from the korean rivers alone we propose that reworking of unit a2 has provided large volumes of muds to unit b resulting in excessive sediment accumulation in the northern seysm much of unit a2 in turn is likely to have originated from erosion of unit a1 in the north this rather unique erosional depositional regime of the seysm is probably owing to the tidal and regional currents characteristic in the southeastern yellow sea

late pleistocene silty tidal rhythmites in the macrotidal flat between youngjong and yongyou islands west coast of korea abstract late pleistocene silty tidal rhythmites developed in the macrotidal flat between youngjong and yongyou islands demonstrate hierarchical tidal cycles ranging from daily to monthly variations associated with synodic tropical and anomalistic cycles on the basis of rhythmicities and textural composition the rhythmites were likely deposited in an upper intertidal flat under a mixed dominantly semi diurnal tidal regime the rhythmites showing gradational contact with overlying cryoturbated silty facies indicating subaerial exposure and subsequent weathering during the last glacial maximum represent the tidal environment during the last highstand or ensuing regression phase of sea level in the late pleistocene

isoseismal map of the 2015 nepal earthquake and its relationships with ground motion parameters distance and magnitude abstract a devastating earthquake of mw 7 8 struck central nepal on 25th april 2015 6 11 25 ut which resulted in more than 9000 deaths and destroyed millions of houses standing buildings roads and electrical installations worth 25 30 billions of dollars are reduced to rubbles the earthquake was widely felt in the northern parts of india and moderate damage have been observed in the northern part of up and bihar region of india maximum intensity ix according to the usgs report was observed in the meizoseismal zone surrounding the kathmandu region in the present study we have compiled available information from the print electronic media and various reports of damages and other effects caused by the event and interpreted them to obtain modified mercalli intensities mmi at over 175 locations spread over nepal and surrounding indian and tibet region we have also obtained a number of strong motion recordings from india and nepal seismic network and developed an empirical relationship between the mmi and peak ground acceleration pga peak ground velocity pgv we have used least square regression technique to derive the empirical relation between the mmi and ground motion parameters and compared them with the empirical relationships available for other regions of the world further seismic intensity information available for historical earthquakes which have occurred in the nepal himalaya along with the present intensity data has been utilized for developing an attenuation relationship for the studied region using two step regression analyses the derived attenuation relationship is useful for assessing damage of a potential future large earthquake earthquake scenario based planning purposes in the region

relationships between instrumental ground motion parameters and modified mercalli intensity in eastern north america a new relationship between modified mercalli intensity mmi and peak ground velocity pgv is developed by comparing instrumentally recorded and inferred historical pgv values to observed mmi for 18 significant earthquakes from eastern north america ena of moment magnitude 3 6 7 25 this pgv mmi relationship is implemented in shakemaps in ontario to estimate ground shaking intensity instrumentally derived mmi given instrumental recordings of pgv corresponding relationships for 5 damped pseudoacceleration psa at frequencies of 1 5 and 10 hz are also developed we compare the results with previous relationships between mmi and ground motion parameters developed for california by wald et al 1999a and atkinson and sonley 2000 we conclude that empirical relationships between mmi and ground motion are significantly different in eastern north america than in california thus such relationships should be assessed for each region where shakemaps are implemented manuscript received 24 october 2003

depositional patterns of sand ridges in tide dominated shallow water environments yellow sea coast and south sea of korea abstract the continental shelf of the yellow sea and the korean south sea is a tide dominated shelf a number of sand ridges occur in this area which form bathymetric highs surveyed were one large sand ridge jangan satoe along the western yellow sea coast and a group of mid shelf sand ridges in the south sea to delineate their depositional pattern and probable origin in tide dominated shallow water environments analyses of sediment samples side scan sonographs and seismic profiles reveal that these ridges show regionally different characteristics in morphology bedforms and sediment the sand ridge in the yellow sea shows a composite form of various bedforms including sand waves and megaripples this ridge is interpreted to be in an accretional active stage maintained by strong tidal currents in contrast the sand ridges on the mid shelf of the south sea show rounded single forms without bedforms on them they are interpreted to represent moribund type sand ridges in the shelf environment which were formed near the shoreline during the holocene sea level transgression these ridges developed off the paleo seomjin river during a period of a stillstand or slow sea level rise approximately between 10 000 and 7000 yrs b p

sediment accumulation in a modern epicontinental shelf setting the yellow sea sediment accumulation in the yellow sea epicontinental shelf environment is investigated on 100 yr and 1000 yr time scales using 210pb and 14c geochronologies the distribution of modern 210pb accumulation rates in the yellow sea reveals that the loci of modern huanghe sediment accumulation are the topset 1 2 mm yr foreset 4 9 mm yr and proximal bottomset deposits 2 4 mm yr of the shandong subaqueous delta which extends south from the shandong peninsula 210pb rates in the distal bottomset deposits of the subaqueous delta in the central and southern yellow sea are generally low 0 3 0 9 mm yr a sediment budget demonstrates that between 9 15 of the annual huanghe discharge is accumulating in the yellow sea about two thirds of this sediment is accumulating in the topset foreset and proximal bottomset deposits of the shandong subaqueous delta with the remaining third accumulating as widespread distal bottomset deposits 14c age dates of subaqueous delta sediments indicate that the thick 40m clinoform structure formed predominantly between 6200 and 4060 yrs b p at rates approaching 20 mm yr observations in the yellow sea as well as on the amazon and ganges brahmaputra shelves demonstrate that subaqueous deltaic stratigraphy is the general rule where major rivers enter energetic shelves whether epicontinental or pericontinental the development of extensive bottomset deposits may be restricted to epicontinental shelf environments and may be diagnostic of sedimentation in this type of setting

large scale sediment bodies and superimposed bedforms on the continental shelf close to the strait of gibraltar interplay of complex oceanographic conditions and physiographic constraints a previously unknown field of large scale sedimentary bodies has been mapped and studied on the continental shelf off the cape trafalgar near the strait of gibraltar with particular emphasis on the relationship between large scale sediment bodies and the superimposed bedforms this study is based on a grid of 975 km of high resolution seismic profiles collected at water depths ranging between 15 and 60 m high variability of large scale sedimentary bodies is attributed to the complex interaction of hydrodynamic agents the most prominent sedimentary features are sand banks and ridges that indicate long term southwest and southward directed sediment transport patterns possibly due to the interplay of two dominant current systems flowing southward and westward these sediment bodies evolve laterally to distinct external geometries such as sand shoals in shallow water and sand sheets in the vicinity of larger sand banks that indicate moderate current velocities in addition pre existing physiography is considered to play a role in the generation of certain sediment bodies developed over inclined surfaces or confined laterally by elevations relationships between superimposed bedforms mostly very large dunes and underlying sediment bodies vary across the study area most superimposed bedforms occur over the complex mosaic of sediment banks and sheets suggesting the interaction of several high energy currents with different directions such as tidal and or wind driven currents copyright 2010 john wiley sons ltd

does the yellow sea warm current really exist as a persistent mean flow does saline water of kuroshio origin intrude into the yellow sea interior by a persistent mean current through the yellow sea warm current or by an intermittently generated wind driven current this very fundamental question is discussed by analyzing comprehensive conductivity temperature depth data collected over the entire southern yellow sea basin and by analyzing satellite tracked drifter trajectories collected in 1996 and 1997 in the southwestern yellow sea relatively saline water 33 0 34 0 psu persists year round implying a northwestward intrusion of cheju warm current water cwcw this water is a mixture of saline cwcw with salinity higher than 34 0 psu and fresh yellow sea waters with salinity 33 0 psu during the winter monsoon the mixed water distribution is tongue shaped apparently intruding from the cwcw area at the same time a strong thermohaline front with a horizontal form similar to the greek letter forms across the southern entrance of the central yellow sea trough and separates the mixed water area from the cwcw during the summer monsoon the cwcw intrusion is weak and the mixed water that intruded in the previous winter monsoon remains inside the trough as its salinity decreases in winter occasional collapses of part of the front on the western side of the trough are observed presumably in response to an imbalance between northwest currents generated by strong northerly wind bursts and southeast tide induced residual currents saline water in the frontal zone may then flush into the southwestern yellow sea through the collapsed area of the front we conclude that the yswc is not a persistent mean current we also conclude that cwcw may be transported to the southwestern yellow sea in winter by the intermittently generated northwest currents on the western slope of the trough which override the tide induced residual currents that flow to the southeast in this part of the basin

fluvial incision and tectonic uplift across the himalayas of central nepal the pattern of fluvial incision across the himalayas of central nepal is estimated from the distribution of holocene and pleistocene terraces and from the geometry of modern channels along major rivers draining across the range the terraces provide good constraints on incision rates across the himalayan frontal folds sub himalaya or siwaliks hills where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces farther north and upstream in the lesser himalaya prominent fill terraces were deposited probably during the late pleistocene and were subsequently incised the amount of bedrock incision beneath the fill deposits is generally small suggesting a slow rate of fluvial incision in the lesser himalaya the terrace record is lost in the high range where the rivers are cutting steep gorges to complement the terrace study fluvial incision was also estimated from the modern channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate this approach allows quantification of the effect of variations in channel slope width and discharge on the incision rate of a river the determination of incision rates requires an additional lithological calibration the two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared in the sub himalaya river incision is rapid with values up to 10 15 mm yr it does not exceed a few millimeters per year in the lesser himalaya and rises abruptly at the front of the high range to reach values of 4 8 mm yr within a 50 km wide zone that coincides with the position of the highest himalayan peaks sediment yield derived from the measurement of suspended load in himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range the observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat ramp flat geometry of the main himalayan thrust fault the morphology of the range reflects a dynamic equilibrium between present day tectonics and surface processes the sharp relief together with the high uplift rates in the higher himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the tibetan plateau driven by late cenozoic climate change or late miocene reactivation of the main central thrust

tidal deposition systems of china s continental shelf with special reference to the eastern bohai sea abstract the continental shelf of china has undergone a large scale marine transgression tidal currents have become the main active agent and have had a profound influence on the deposition and geomorphology of the shelf the continental shelf of china has five modern tidal deposition systems 1 the eastern part of the yellow sea 2 the eastern part of the bohai sea 3 off the mouth of yangtze river 4 to the west of taiwan and 5 the strait of qiongzhou when the tidal current speed is above 150 cm s erosion dominates and reciprocating currents form deep scour furrows when the tidal current speed is 50 to 150 cm s deposition is dominant and tidal currents form tidal shoals i e tidal sand ridges and tidal sand sheets whose margins are near an absolute ellipticity value for the m2 tidal component of 0 4 when the absolute m2 value is less than 0 4 a reciprocating current is strong enough to form tidal sand ridges when the absolute value is above 0 4 a rotating current increases so as to form a tidal sand sheet tidal deposition material came mainly from tidal erosion and locally redeposition of late pleistocene sediments and from the neighbouring sea bottom the tidal deposition system in the eastern bohai sea is a typical example it consists of the laotieshan channel scour furrow the liaodong shoal sand ridges and the bozhong shoal sand sheet the maximum tidal current speed in the laotieshan channel where strong erosion occurs is up to 250 cm s in the liaodong shoal the maximum tidal current speed is 64 115 cm s and the absolute ellipticity value of the m2 tidal component is less than 0 4 in the bozhong shoal the maximum tidal speed is 58 79 cm s and the absolute ellipticity value of the m2 tidal component is above 0 4 the small scale bedforms surveyed in detail in the area show that the sand ridges and sand sheet are still under the action of tidal current processes at the present time based on the interpretation of tidal currents bedforms and sediment thickness it is inferred that the general direction of sediment transport within the study area is nnw from the laotieshan channel to the liaodong and bozhong shoals the small scale bedforms in the detailed survey area indicate a local net sediment transport from south to north

late quaternary evolution of the yellow east china sea tidal regime and its impacts on sediments dispersal and seafloor morphology the evolution of a tidal current field in the yellow sea and east china sea yecs in response to the sea level rise since the last glacial maximum lgm was investigated using a two dimensional tidal model with special attention to changes in the sedimentary environment of the continental shelf region it was found that tidal currents on the yecs shelf have generally been semi diurnal throughout the post glacial stages with f ratio index of diurnal inequality and s2 m2 ratio index of spring neap cycle remaining similar to present on the other hand the spatial distribution of the tidal bottom stress associated with m2 and m4 tidal currents changed greatly during the transgression as the sea level rose two core regions showing high bottom stress values migrated shoreward from cheju island toward the west coast of korea and along the retreat path of the paleo changjiang estuary distribution of extremely intense tidal bottom stress suggested that intense tidal reworking may have occurred at sea levels from 90 to 45 m in the southeast yellow sea and at 75 to 60 m off the paleo changjiang estuary the latter of which agreed with the timing of a large terrigenous organic c flux observed on the shelf slope distribution of slightly weaker bottom stress indicated that the sand ridges off the changjiang estuary and in the southeast yellow sea also might have formed at during those periods on the other hand when the sea level was between 45 and 15 m the tidal bottom stress was generally not strong enough to invoke significant reworking even though the stress intensity may be stronger than present correlation with modern and relict sedimentary features suggested that the tidal process have played a significant role on the reworking and deposition of sediments on the yecs shelf

lower edge of locked main himalayan thrust unzipped by the 2015 gorkha earthquake faults are unlocked by earthquakes analysis of seismic data from the 2015 nepal earthquake shows that only part of the main himalayan thrust fault was unzipped by the quake leaving much of the fault locked and ready to slip in a future event

relationship between peak ground acceleration peak ground velocity and intensity in taiwan based on the strong motion data set from the 1999 chi chi taiwan earthquake and a shaking damage statistics database we investigated the correlations between strong ground motions and earthquake damage fatalities and building collapses through a regression analysis as a result the current earthquake intensity scale i t is placed on a more reliable instrumental basis this is necessary for the real time seismic monitoring operation in taiwan where programs for earthquake rapid reporting rrs and earthquake early warning ews are actively pursued it is found that the earthquake damage statistics give a much closer correlation with the peak ground velocity pgv than with the peak ground acceleration pga the empirical relationship between pgv and the intensity i t determined in this study can be expressed as i mathrm t 2 14 times mathrm log 10 mathrm pgv 1 89 this pgv based intensity is particularly useful in real time applications for damage prediction and assessment as the damage impact of high pgv is much more important for mid rise and high rise buildings that are characteristic of a modern society for smaller earthquakes m m

effect of sea level rise and tidal current variation on the long term evolution of offshore tidal sand ridges abstract tidal sand ridges are large scale bedforms that occur in the offshore area of shelf seas they evolve on a time scale of centuries due to tide topography interactions while being further shaped by wind waves during their evolution ridges are also affected by changes in sea level strength and direction of the tidal current according to their present day behavior ridges are classified as active sand transport everywhere quasi active sand transport only on parts of the ridges and inactive no sand transport anywhere using a nonlinear morphodynamic model the present study extends earlier work by investigating the effect of sea level rise and changes in the amplitude and principal direction of the tidal current on the growth time and height of active tidal sand ridges besides the role of sea level rise and tidal current variation in the presence of quasi active inactive ridges is explored two specific settings are considered which are characteristic for the dutch banks in the north sea and for sand ridges in the celtic sea the time range considered here is less than 20 000 years roughly the period from the last glacial maximum to the present generally active tidal sand ridges occur if the tidal current amplitude is larger than 0 5 m s for these ridges with increasing rates of sea level rise their growth time becomes longer and the root mean square height keeps on increasing a smaller initial tidal current amplitude gives rise to a larger growth time while changes in the principal current direction have a minor effect on the characteristics of the ridges on the considered time scale assuming a constant wave climate quasi active tidal sand ridges occur mainly as a result of a decreasing tidal current amplitude such that the effective velocity in the sense of stirring sand becomes smaller than the critical velocity for sand erosion the ridges further become inactive on a time scale that depends inversely on the rate of sea level rise modeled ridges are compared with observed ridges similarities are found and quantitative differences are explained

seismic ground response studies in olympia washington and vicinity relative seismic ground response characteristics in the cities of olympia lacey and tumwater washington were determined from analysis of instrumentally recorded ground motion induced by blasts at an open pit coal mine near centralia washington a ground response function grf defined as the ratio of fourier spectral amplitudes at an alluvium site to spectral amplitudes on hard rock is a measure of amplification of seismic waves by localized site conditions grf values in three frequency bands 0 5 to 1 0 hz 1 0 to 2 0 hz and 2 0 to 4 0 hz were compared with observed modified mercalli mm intensities from the 29 april 1965 puget sound earthquake and with mapped surficial geologic units typically the grf values relate well with the surficial geological units in addition mm intensities within the v to vii range appear to be directly related to the frequencies within the 0 5 to 4 0 hz bandwidth such that mm v intensity sites had a lower grf value in the 2 0 to 4 0 hz bandwidth as compared to the 0 5 to 2 0 hz bandwidth and the mm vii intensity sites had higher grf values in the 2 0 to 4 0 hz bandwidth as compared to the 0 5 to 2 0 hz bandwidth the set of grf values determined for the city of olympia and its vicinity should be useful in formulating a theoretical relative ground response model for the southern puget sound area

origin of inner shelf mud deposit in the southeastern yellow sea huksan mud belt abstract a variety of previous sedimentological results together with newly obtained hydrodynamic data are summarized and reinterpreted with respect to the most likely origin of the huksan mud belt hmb in the southeastern yellow sea the hmb consists of two mud units that have similar grain texture and clay mineralogy but can be differentiated on seismic profiles because the lower unit is generally harder than the watery upper unit the hydrographic measurements together with satellite imagery clearly indicate that the suspended plume covering the hmb originates from the west coast of korea the suspended plume becomes enhanced by winter monsoon winds beginning in late fall most of the studies of clay mineralogy geochemistry and isotherm distribution also suggest that the hmb has been derived from the west coast of korea particularly from the keum river an approximate evaluation of the depositional time for the hmb based on its dimensions and the discharge rate of the keum river suggests a time duration of the order of 14 000 years hydrodynamic measurements across two transects over the northernmost hmb reveal that suspended matter travels southwest toward the main body of the hmb in a well constrained corridor ultimately connected with the keum river time series 12 5 h hydrodynamic measurements at a site over the hmb suggest that the winter season suspended plume carries concentrations of suspended matter one to two orders of magnitude higher than those of the summer silt grains of 5 6 well sorted through numerous resuspension events settle out onto the hmb forming distinctive silt laminae alternating with clay rich laminae

headland associated banner banks generated during the last deglaciation near the strait of gibraltar gulf of cadiz sw spain the inception and evolution of large scale bedforms on the barbate platform gulf of cadiz sw iberian peninsula are investigated based on a detailed study of multibeam bathymetric data high resolution seismic profiles and tidal current simulations elongated rocky outcrops and several large scale bedforms classified as sand banks were identified on the platform barbate zahara el palmar el varadero and canos de meca banks the barbate and zahara banks exhibit the most complex internal stratigraphic architecture which comprises five seismic units the basal unit u1 is interpreted as incised valley infill and is overlain by nearshore bars u2 two high energy growth phases u3 and u4 that combine progradation and accretion form the present day external bank shape superimposed bedforms covered these banks under the modern hydrodynamic regime u5 the multiphase accretion and progradation of u3 and u4 in the zahara and barbate banks were closely linked to the presence of a palaeo headland termed here as palaeo cape trafalgar and strong tidal current eddies that resulted from the progressive flooding of the barbate platform during the last deglaciation this configuration was relatively stable while the rocky outcrops were exposed to sub aerial conditions forming a palaeo coast with coastal bluffs we suggest that during this period of coastal stabilization u3 and u4 grew as banner banks on either side of the palaeo cape trafalgar the present study proposes that the configuration of palaeo headland associated with palaeo banner banks zahara and barbate banks along each side of the palaeo cape trafalgar represents a transgressive analogue model of headland associated tidal bank systems developed in funnel shaped coastal systems terminating in narrow straits

constraints on himalayan deformation inferred from vertical velocity fields in nepal and tibet spirit leveling data from the nepal himalaya between 1977 and 1990 indicate localized uplift at 2 3 mm yr in the lesser himalaya with spatial wavelengths of 25 35 km and at 4 6 mm yr in the greater himalaya with a wavelength of 40 km leveling data with significantly sparser spatial sampling in southern tibet between 1959 and 1981 suggest that the himalayan divide may be rising at a rate of 7 5 5 6 mm yr relative to central tibet we use two dimensional dislocation modeling methods to examine a number of structural models that yield vertical velocity fields similar to those observed although these models are structurally nonunique dislocation models that satisfy the data require aseismic slip rates of 2 7 mm yr on shallow dipping faults beneath the lesser himalaya and rates of 9 18 mm yr on deep thrust faults dipping at 25 n near the greater himalaya unfortunately the leveling data cannot constrain long wavelength uplift 100 km across the himalaya and unequivocal estimates of aseismic slip in central nepal are therefore not possible in turn the poor spatial density of leveling data in southern tibet may inadequately sample the processes responsible for the uplift of the greater himalaya despite these shortcomings in the leveling data the pattern of uplift is consistent with a crustal scale ramp near the greater himalaya linking shallow northward dipping thrust planes 3 6 beneath the lesser himalaya and southern tibet aseismic slip on the potential rupture surface of future great earthquakes beneath the nepal himalaya south of this ramp appears not to exceed 30 of the total convergence rate between india and southern tibet resulting in an accumulating slip deficit of 13 8 mm yr

himalayan seismic hazard the devastating earthquake in bhuj on 26 january 2001 highlighted the high earthquake risk in the indian region of gujarat in their perspective bilham et al warn that major earthquakes may be expected in another part of india the himalayan arc an analysis of historic earthquakes suggests that several major earthquakes are overdue in this region but that recent low activity has focused attention away from the himalayan arc projections from earlier earthquakes suggest that just one of the possibly overdue himalayan earthquakes may lead to 200 000 predictable fatalities

magnitude calibration of north indian earthquakes this article is concerned primarily with the evaluation of the size and location of northern indian and southern tibetan earthquakes during the last 200 yr it draws attention to the problems of assessing intensity of early and more recent earthquakes in a built environment which is different from that for which the intensity scale has been constructed and to the way in which isoseismals are drawn through a re evaluation of intensities and a reassessment of isoseismals a formula for the estimation of surface wave magnitude using isoseismal radii is derived this formula is used to estimate the surface wave magnitudes of 16 earthquakes that occurred in the region between 1803 and 1900 this study shows that it is possible to calculate accurate surface wave magnitudes for earthquakes that occurred before the advent of the scale and that there is no need to resort to empirical formulae for the assessment of the size and seismic moment release of pre 20th century earthquakes also derived are formulae for the conversion of ms to m0 in total locations surface wave magnitudes and m0 estimates are presented for 43 important events that occurred in the region between 1803 and 1974 eight of which were in the lower crust or were subcrustal we find that the m0 ms scaling for india yields smaller ms than the global relation and that the methodology used can help to evaluate more realistic slip rates as well as to address other issues related to earthquake hazard in northern india

late pleistocene left lateral slip rates of the gulang fault and its tectonic implications in eastern qilian shan ne tibetan plateau china abstract the late pleistocene deformation pattern in the eastern qilian shan remains controversial study of the geometry and slip rate of the fault holds crucial value for better understanding the regional deformation pattern the active e w trending gulang and tianjing shan fault zone is located in the southern boundary of the tengger desert which plays a significant role in tectonic deformation and slip transfer in the ne tibetan plateau geomorphic mapping of the active fault traces reveal that the gulang fault is composed of two segments separated by the guanjia tai pull apart basin offset geomorphic features indicate that the gulang fault appears to be primarily sinistral strike slip with no reverse component based on offset gullies terraces and optically stimulated luminescence dating of offset related sediments we obtain a consistent late pleistocene slip rate of 2 5 mm a along the western and eastern segments of the gulang fault meanwhile the slip vectors indicate the gulang fault redistributes strain and transforms displacement along the haiyuan fault accommodating the westward motion of the gobi alashan block moreover a devastating earthquake of ms 8 0 struck gulang on 23rd may 1927 geomorphically fresh fault scarps and surface rupture zone are observed at gulang fault we modify the modified mercalli intensities mmi and revise the isoseismal map for the gulang earthquake combining with the high resolution deep seismic reflection data the gulang fault may be the source of the earthquake regionally gps velocities indicate that faulting crustal shortening and basin block rotation accommodate deformation of the plateau s northern margin in conclusion the fault geometry kinematics and regional gps velocities reflect that this region experiences eastward movement of the northeastern tibetan plateau relative to the gobi alashan

development of stratigraphy and sediment distribution in the northeastern yellow sea during holocene sea level rise abstract a succession of holocene deposits in the northeastern yellow sea were interpreted in a sequence stratigraphic context and sedimentology of each deposit was characterized based on analyses of high resolution seismic profiles and sediment cores taken along a transect thin 3 m transgressive sediments that accumulated through shoreface erosion during the rapid sea level rise in the early holocene overlie a subaerially eroded low gradient late pleistocene platform on the present day inner shelf region cores reveal marine sands over tidal estuarine sandy muds with an intervening rather indistinct ravinement surface in the deepest shelf area these early holocene tidal estuarine deposits remain exposed at the seabottom in the mid o late holocene two contrasting deposits of the highstand type deltaic clayey mud and tidal sand ridges began to accumulate in response to slower rates of sea level rise a series of tidal sand ridges in the nearshore area migrated offshore over the transgressive sand sheet and a deltaic watery mud prograded discordantly over consolidated tidal estuarine deposits in the central shelf the transgressive facies relationships present a model for macrotidal epicontinental sea settings subject to low wave energy and reduced sediment supply

reconciliation of late quaternary sea levels derived from coral terraces at huon peninsula with deep sea oxygen isotope records a major discrepancy between the late quaternary sea level changes derived from raised coral reef terraces at the huon peninsula in papua new guinea and from oxygen isotopes in deep sea cores is resolved the two methods agree closely from 120 ka to 80 ka and from 20 ka to 0 ka ka 1000 yr before present but between 70 and 30 ka the isotopic sea levels are 20 40 m lower than the huon peninsula sea levels derived in earlier studies new high precision u series age measurements and revised stratigraphic data for huon peninsula terraces aged between 30 and 70 ka now give similar sea levels to those based on deep sea oxygen isotope data planktonic and benthic 18o data using the sea level and deep sea isotopic data oxygen isotope ratios are calculated for the northern continental ice sheets through the last glacial cycle and are consistent with results from greenland ice cores the record of ice volume changes through the last glacial cycle now appears to be reasonably complete