crustal structure seismic stratigraphy and rift processes of the continental margin off eastern canada ocean bottom seismic refraction results off nova scotia two crustal seismic refraction profiles were obtained on the continental margin of eastern canada these lines were located on the upper continental rise and on the outer continental shelf off nova

focal mechanisms of three earthquakes in finland and their relation to surface faults abstract focal mechanisms for three recent earthquakes in finland are determined using p wave polarities together with sv p and sh p phase amplitude ratios the events occurred on may 11 2000 in toivakka central finland ml 2 4 on september 15 2000 in kuusamo northeastern finland ml 3 5 and on may 2 2001 in kolari western finnish lapland ml 2 9 in order to obtain reliable estimates of the source parameters one dimensional crust and upper mantle velocity models are derived for the epicenter areas from deep seismic sounding results the starting models are modified by one dimensional ray tracing using the earthquake observations the events are relocated by employing p and s phase arrival times from the nearest seismic stations and the final velocity models synthetic waveforms calculated with the reflectivity method are used to further constrain and verify the source and structural parameters the toivakka earthquake indicates thrust or reverse faulting mechanism at a depth of 5 km after comparison with aeromagnetic and topographic data we suggest the eastward dipping nodal plane 358 42 was the fault plane the best fitting fault plane solution of the kolari earthquake suggests pure thrust faulting at a depth of 5 km the nodal plane striking 035 30 correlates well with surface observations of the postglacial possibly listric fault systems in the source area the kuusamo earthquake focal depth 14 km has a normal faulting mechanism with the nodal planes trending 133 47 or 284 47 preference is given to the sw dipping nodal plane as it seems to coincide with topographic and magnetic lineament directions that have been active after the last ice age the three earthquakes have occurred in old precambrian faults and shear zones which have been reactivated the reactivated faults are favourably oriented in the local stress field

broadband modelling along a regional shield path harvard recording of the saguenay earthquake summary the saguenay earthquake 1988 november 25 is one of the first large shield type events recorded by a broadband high dynamic range instrument the streckeisen system installed at harvard station hrv the event is sufficiently large to be well recorded teleseismically and thus the source characteristics can be determined by independent means and considered known this allows a detailed study of the propagational effects along this path at an epicentral distance of 625 km where the strengths of the surface waves can be compared with the crustal body phases broadband modelling using standard analytical techniques and flat layered models works amazingly well over the period range of 0 5 20 s a detailed strategy for modelling broadband regional phases is given in terms of a decomposition of the vertical and radial seismograms into three segments pnl containing pn ppn spn pmp p coupled pl waves snl containing sn ssn sms etc and the fundamental rayleigh waves information about the upper crust is obtained from the fundamental rayleigh waves while crustal thickness and velocity gradients in the mantle are obtained from pnl and snl this particular crustal model has a thickness of 35 km with a sharp moho and a substantial gradient in the top 20 km of the mantle 0 01 km s 1 per km for both p and s velocities the mantle velocities 8 2 and 4 55 km s 1 are slower than expected for a shield environment attenuation is not required for waveform modelling or for absolute amplitude estimation

source parameters and tectonic implications of aftershocks of the mw 7 6 bhuj earthquake of 26 january 2001 we present and discuss the spatial distribution of more than 1000 aftershocks of the largest continental intraplate earthquake to occur during the modern seismological period the data were recorded on a network of eight portable digital seismographs deployed for 3 weeks starting 17 days after the mainshock we have calculated high quality single event locations based on a 1d velocity model determined for the region for earthquakes with magnitudes between 2 and 5 aftershock locations reveal activity concentrated on a nearly east striking south dipping plane trapezoidal in outline the active zone tapers from about 45 km along strike at the shallow end which is about 5 km deep to no more than 25 km long at a depth of 35 km the total rupture area was about 1300 km 2 we estimate the static stress drop of the mainshock at 16 2 mpa aftershocks extend nearly through the entire crust with concentrations in the lower crust at about 26 km and in the upper crust at about 10 km the fault that ruptured was not mapped at the surface and not known to have been active prior to the 2001 earthquake the aftershock data are consistent with the bhuj earthquake resulting from reactivation in contraction of a fault formed under extension within a failed rift

investigations of soil cracking and preferential flow in a weighing lysimeter filled with cracking clay soil an improved understanding of deep drainage processes in irrigated cracking soils is needed for sustainable irrigation management to investigate the effect of crack dynamics and macropore flow on drainage in cracking soils a series of irrigation experiments was carried out in a weighing lysimeter subsurface soil cracks of the initially very dry soil were investigated with a videoscope and changes in the surface expression of cracks in response to irrigation events were monitored by time lapse photography a bromide tracer was applied to one irrigation event variations in the combined soil and moisture mass and the volume of drainage out of the soil column was logged and the drainage ec and bromide content were determined no drainage occurred out of the soil column during the first 3 out of 6 irrigation events even though substantial surface runoff into the cracks occurred and at least initially soil cracks provided an uninterrupted flow path through the profile the breakthrough of the bromide tracer as well as an initially low ec of the drainage water indicate that preferential flow accounted for a substantial part of the first of the two drainage events even though the soil cracks were sealed on the surface at the onset of the irrigation causing the drainage the results show that lateral infiltration of macropore flow into the soil matrix can be substantial and should not be neglected while simulating macropore flow and deep drainage in cracking soils the results also indicate that soil cracks can remain pathways for preferential flow even after they are closed at the soil surface the type of water application appears to have an impact on the location of crack formation with flood irrigation favouring reappearance of cracks at previous crack locations and simulated rainfall resulting in shifting crack locations

tectonic history of northern alaska canadian arctic and spitsbergen regions since early cretaceous the correlation of interregional unconformities structures and magmatic activity suggests tectonic events in the arctic were controlled by the early cretaceous collision and combined interaction of the eurasian and north american plates in northeastern ussr the late mesozoic cenozoic accretion of exotic terranes in the north pacific and north atlantic arctic sea floor spreading contemporaneous with the accretion of exotic terranes in northeastern ussr and interior alaska the brooks range developed as a cordilleran mountain belt at the same time during the cretaceous between 125 and 85 ma the canada basin spread north of alaska about a pole of rotation located southeast of the mackenzie delta the alaskan plate was first a part of the northwestern nose of the north american plate when the canada basin spreading ceased the basin was severed by movement along the kaltag and associated strike slip faults and became a part of the northeasterly moving eurasian plate the kaltag fault system is inferred to extend from the western bering sea at the northern end of the kuril arc through alaska and along the outer margin of the arctic islands to the north of greenland it is postulated to have formed the transform boundary between the north american and eurasian plates with the alaskan plate bonded to the latter since the late cretaceous the late eocene change in the direction of pacific spreading terminated the subduction related laramide orogeny as well as the right lateral displacements of major cordilleran faults such as the tintina and denali faults changing eurasian plate movement may have caused most of the strong middle eocene right lateral displacement along the kaltag fault zone continuing displacement from the southwest caused the development of a late cenozoic foldbelt in coastal northeastern alaska herein named the romanzof disturbance coeval with balancing right lateral movement along the kaltag fault zone the huge undrilled marsh creek anticline is a part of this foldbelt seismic data show evidence of middle eocene compression followed by weak extension east of the kaltag fault zone in the beaufort sea the same activity is evident at the northeastern end of the north american plate at nares strait located between the arctic islands and greenland eocene fault movement along the kaltag nares strait and de geer separating greenland and spitsbergen transforms is regarded as complementary the presence of eocene thrust zones located on the western side of nares strait and in western spitsbergen suggests that northward movement of the greenland plate formed both the transforms and the thrust belts

a method for measuring the development of surface cracks in soils application to crack development after lowland rice abstract surface cracks develop in many clay soils as they dry since they are difficult to adequately sample in most volumetric samples it is useful to measure them so that volumetric measurements of water content for example can be corrected a method for measuring cracks in soils is described a transect consisting of six linked semi circles each of 1 m diameter is used to count intercepts with the cracks which allows estimation of the length of cracks per unit area la the semi circular shape avoids any bias due to preferred orientation of the cracks to minimise the effort required to achieve the greatest accuracy which depends on the number of cracks counted and not the transect length 50 intercepts are counted per replicate transect after which any remaining intercepts with the current semi circle are counted in addition crack depth and surface width are measured at a total of 60 intercepts over all replicate transects this allows calculation of means for depth and width mean vertical cross sectional area and the volume of crack per unit area can be calculated by assuming a rectangular triangular or square root shape model for the crack cross section the depth functions of la and vv crack volume per unit volume can also be calculated although the latter requires assumptions about crack shape the method is illustrated by application to two soils puddled for rice during the first four week drying after field drainage

effects of lithology and land use on storm run off in east luxembourg for a large part of the year the forested catchments in the keuper formation of east luxembourg produce more direct run off on a storm basis than paired cultivated catchments the occurrence of shrinkage cracks their pronounced opening and closing and the occurrence of natural pipes in the forested environment play a major role in explaining this phenomenon the effect of land use on storm run off is studied in relation to that found for lithology in the same area

hillslope run off thresholds with shrink swell clay soils irrigation experiments on 12 instrumented field plots were used to assess the impact of dynamic soil crack networks on infiltration and run off during applications of intensity similar to a heavy rainstorm water was seen being preferentially delivered within the soil profile however run off was not observed until soil water content of the profile reached field capacity and the apertures of surface connected cracks had closed 60 electrical resistivity measurements suggested that subsurface cracks persisted and enhanced lateral transport even in wet conditions likewise single ring infiltration measurements taken before and after irrigation indicated that infiltration remained an important component of the water budget at high soil water content values despite apparent surface sealing overall although the wetting and sealing of the soil profile showed considerable complexity an emergent property at the hillslope scale was observed all of the plots demonstrated a strikingly similar threshold run off response to the cumulative precipitation amount copyright 2014 john wiley sons ltd

marine heat flow observations on the canadian arctic continental shelf and slope abstract we present 36 new heat flow measurements grouped within five separate sites on the canadian arctic continental shelf and slope between 95 115 w and 80 82 n observations consist of temperature gradients and in situ thermal conductivity using a modified marine type multiple penetration probe with a length of 4 6 m repeat measurements from nearby locations at different times of the year indicate that for depths deeper than 200 m the bottom water remains sufficiently stable to allow shallow measurements to characterize the deeper geothermal flux in this respect the cold ice covered deep water arctic margin is unique among the world s passive continental margins using these data we construct a preliminary geothermal transect between the continental sverdrup basin to the south and the oceanic canada basin to the north values of 35 45 mw m 2 exist on the axel heiberg headland nansen channel and on the continental slope and indicate a broad scale reduction from higher values of 55 60 mw m 2 within the canadian basin to values of 40 50 mw m 2 within the sverdrup basin in contrast there is a zone of high heat flow with well constrained values of 80 mw m 2 within peary channel low values in the northeastern sector of the margin suggest that the early tertiary eurekean orogen near ellesmere island has not thermally affected the margin based on calculations for pure shear extension the 15 mw m 2 reduction across the continental margin suggests that the canada basin proper may not have opened until late cretaceous unless the pre existing continental crust contains an extremely low amount of radiogenic material lithospheric models cannot account for the high values in peary channel which may indicate water movement within the sedimentary basin

the effect of mole drainage on the hydrological response of a swelling clay soil abstract the results of a plot experiment to determine the effects of mole drainage on the hydrological response of a swelling clay soil under pasture are described it is shown that the response is very dependent on antecedent moisture conditions and that higher peak flows may be generated under relatively dry conditions on the drier drained plot this appears to be related to the generation of flows in interpedal macropores supplying water to the mole drains under wet conditions the hydraulic efficiency of the macropores is reduced by swelling of the clay and surface saturation develops on the undrained plot this results in generally higher peak discharges than from the drained plot recession discharges and total water yields are almost always higher from the drained plot the implications of this work are that it may be very difficult to detect or model the influence of clay land drainage on river flows

recurrent events on a quaternary fault recorded in the mineralogy and micromorphology of a weathering profile yangsan fault system korea recurrence characteristics of a quaternary fault are generally investigated on the basis of field properties that are rapidly degraded by chemical weathering and erosion in warm humid climates here we show that in intense weathering environments mineralogical and micromorphological investigations are valuable in paleoseismological reconstruction a weathering profile developed in late quaternary marine terrace deposits along the southeastern coast of the korean peninsula was disturbed by tectonic movement that appears to be a simple one time reverse faulting event based on field observations a comparative analysis of the mineralogy micromorphology and chemistry of the weathering profile and fault gouge however reveals that both the microfissures in the deformed weathering profile and larger void spaces along the fault plane were filled with multi stage accumulations of illuvial clay and silt minerals of detrital origin suggesting a repetition of fissuring and subsequent sealing in the weathering profile as it underwent continuous mineralogical transformation and particle translocation we reconstruct a sequence of multiple faulting events unrecognized in previous field surveys which requires revision of the view that the korean peninsula was tectonically stable during the late quaternary

topographic controls upon soil macropore flow macropores are important components of soil hydrology the spatial distribution of macropore flow as a proportion of saturated hydraulic conductivity was tested on six humid temperate slopes using transects of tension infiltrometer measurements automated water table and overland flow monitoring allowed the timing of and differentiation between saturation excess overland flow and infiltration excess overland flow occurrence on the slopes to be determined and related to tension infiltrometer measurements two slopes were covered with blanket peat two with stagnohumic gleys and two with brown earth soils none of the slopes had been disturbed by agricultural activity within the last 20 years this controlled the potential for tillage impacts on macropores the proportion of near surface macropore flow to saturated hydraulic conductivity was found to vary according to slope position the spatial patterns were not the same for all hillslopes on the four non peat slopes there was a relationship between locations of overland flow occurrence and reduced macroporosity this relationship did not exist for the peat slopes investigated because they experienced overland flow across their whole slope surfaces nevertheless they still had a distinctive spatial pattern of macropore flow according to slope position for the other soils tested parts of slopes that were susceptible to saturation excess overland flow e g hilltoes or flat hilltops tended to have least macropore flow to a lesser extent for the parts of slopes susceptible to infiltration excess overland flow the proportion of macropore flow as a component of infiltration was also smaller compared with the rest of the slope the roles of macropore creation and macropore infilling by sheet wash are discussed and it is noted that the combination of these may result in distinctive topographically controlled spatial patterns of macropore flow copyright 2008 john wiley sons ltd

reflection experiment on a floating ice platform summary preliminary analysis of a multifold seismic survey on a floating ice platform northwest of axel heiberg island along the canadian portion of the continental margin of the arctic ocean revealed a structurally complex basement at a depth beyond 4000 m the basement is covered with high velocity 5000 dsec rock types the results conform to the anticipated geologic model for regions of passive margins

efficient calculation of complete differential seismograms for laterally homogeneous earth models summary differential seismograms the sensitivity of the seismogram to perturbations of parameters of the earth model are essential for waveform modelling with iterative non linear optimization techniques the growing number of broad band highdynamic range fixed and portable stations provide a rich data set of regional distance events with accurate locations and source mechanisms that are ideal for modelling lithospheric structure an efficient technique for calculating differential seismograms for complete synthetic seismograms in laterally homogeneous earth models will significantly decrease the computational burden of seismic waveform inverse modelling the technique we present here is equivalent to computing three synthetic seismograms in multilayered models contrasted with n 1 seismograms for a typical brute force approach which reduces the work to 3 n 1 or about a 90 per cent saving for 30 layers the lateral homogeneity requirement will yield path averaged structures which may form the basis for later tomographic studies to resolve lateral variations

a field method for measuring short circuiting in clay soils abstract a field method is described for measurement of short circuiting which is defined as vertical flow of free water along the walls of continuous macropores in unsaturated soil a cylinder with a diameter and height of 20 cm is filled with undisturbed surface soil and is placed on a perforated disk in a funnel the funnel is supported to allow periodic measurement of the volume of outflow from the soil the assembly is placed along the track of a spray gun which is commonly used for sprinkling irrigation at least four samples can be measured during one run the method is illustrated by discussing the measured short circuiting in surface soils of 1 a heavy clay soil 2 a light clay soil with two different types of structure in and adjacent to potato ridges and 3 a heavy clay soil with two types of surface microrelief short circuiting is unfavourable because water moves rapidly beyond the root zone without moistening and leaching the soil between the macropores the water may carry surface applied fertilizers

clay fine fissuring monitoring using miniature geo electrical resistivity arrays this article describes a miniaturised electrical imaging resistivity tomography technique to map the cracking pattern of a clay model the clay used was taken from a scaled flood embankment built to study the fine fissuring due to desiccation and breaching process in flooding conditions the potential of using a miniature array of electrodes to follow the evolution of the vertical cracks and number them during the drying process was explored the imaging technique generated two dimensional contoured plots of the resistivity distribution within the model before and at different stages of the desiccation process the change in resistivity associated with the widening of the cracks were monitored as a function of time experiments were also carried out using a selected conductive gel to slow down the transport process into the cracks to improve the scanning capabilities of the equipment the main vertical clay fissuring network was obtained after inversion of the experimental resistivity measurements and validated by direct observations

the 1985 86 western bohemia earthquakes modelling source parameters with synthetic seismograms abstract a major swarm of microearthquakes main shock m l 4 6 occurred in december 1985 and january 1986 in the western bohemia region 50 2 n 12 4 e here we revisit the 1985 86 series by modelling some pronounced features of the observed p waveforms frequently seen in the records of the cll brg and the grf seismograph stations travel times and waveforms can be explained by a simple two layer crustal model consisting of an upper crust with v p 5 9 km s and thickness t 18 km and a lower crust with v p 6 8 km s and t 11 km the crust mantle boundary is at 29 km depth waveforms recorded at distances between about 100 and 120 km consist of a low amplitude first p wave which has travelled through the lower crust this phase is followed about 0 5 to 1 s later by the large amplitude main event about 3 s after the main event another phase stands out with similar amplitude it probably represents the depth phase sp m p which leaves the focus upwards as an s wave is converted at the surface to p and then follows the path of p m p the reflection from the crust mantle boundary to the receiver we used this depth phase to constrain the focal depth of the main shock to 9 km depths of the stronger events m l 3 of the swarm are within the depth range from 7 to 10 km inversion of body wave amplitudes and p wave polarities for the focal mechanism of the main event reveals a strike slip mechanism which agrees well with previously published results

the november 2017 mw 5 5 pohang earthquake a possible case of induced seismicity in south korea the moment magnitude mw 5 5 earthquake that struck south korea in november 2017 was one of the largest and most damaging events in that country over the past century its proximity to an enhanced geothermal system site where high pressure hydraulic injection had been performed during the previous 2 years raises the possibility that this earthquake was anthropogenic we have combined seismological and geodetic analyses to characterize the mainshock and its largest aftershocks constrain the geometry of this seismic sequence and shed light on its causal factors according to our analysis it seems plausible that the occurrence of this earthquake was influenced by the aforementioned industrial activities finally we found that the earthquake transferred static stress to larger nearby faults potentially increasing the seismic hazard in the area

resolving focal depth in sparse network with local depth phase spl a case study for the 2011 mineral virginia earthquake sequenceresolving focal depth in sparse network with local depth phase spl

focal mechanisms of recent earthquakes in the southern korean peninsula summary we evaluate the stress field in and around the southern korean peninsula with focal mechanism solutions using the data collected from 71 earthquakes ml 1 9 5 2 between 1999 and 2004 for this the hypocentres were relocated and well constrained fault plane solutions were obtained from the data set of 1270 clear p wave polarities and 46 sh p amplitude ratios the focal mechanism solutions indicate that the prevailing faulting types in south korea are strike slip dominant oblique slip faultings with minor reverse slip component the maximum principal stresses 1 estimated from fault slip inversion analysis of the focal mechanism solutions show a similar orientation with e w trend 269 275 and low angle plunge 10 25 for all tectonic provinces in south korea consistent with the e w trending maximum horizontal stress hmax of the amurian microplate reported from in situ stress measurements and earthquake focal mechanisms the directions of the intermediate 2 and minimum 3 principal stresses of the gyeongsang basin are however about 90 deg off from those of the other tectonic provinces on a common 2 3 plane suggesting a permutation of 2 and 3 our results incorporated with those from the kinematic studies of the quaternary faults imply that nnw to ne striking faults dextral strike slip or oblique slip with a reverse slip component are highly likely to generate earthquakes in south korea

the nature of the tile drain outfall hydrograph in heavy clay soils abstract the outfall hydrographs of agricultural underdrainage installations in a heavy clay soil are examined over four drainage seasons seasonal differences in drainage response to rainfall are attributed to antecedent soil conditions and these are controlled in part by the influence of topography upon downslope seepage bowl shaped landforms are kept moister by convergent interflow streamlines and drainage follows the onset of rainfall most quickly in winter well drained convex slopes on the other hand are subject to greater summer desiccation and deep cracks convey autumn rainwater directly into the subsoil so that drainage response here is quicker at this time of year peak drain flow occurs at 3 6 hr after the rainfall centroid in winter for both topographical situations but median values of peak discharge can be up to four times those of the non winter drainage period during which absorption of rainfall by the soil leads to a reduction in drainage outfall the largest risk of flooding in river basins where under drainage is widespread comes from complex storms secondary peaks in the drainage hydrograph not only arrive earlier by an average of 1 38 hr but are also shown to reach discharges more than three times those associated with simple storms having equivalent rainfalls

did two massive earthquakes in the holocene induce widespread landsliding and near surface deformation in part of the ottawa valley canada recent evidence based on ages of large landslides and the existence of severely disturbed terrain in champlain sea sediments to the east of ottawa suggests that this area may have been the site of two of the most geologically destructive earthquakes in eastern canada the walls of several paleochannels downcut into sensitive marine clayey silts are scarred by numerous large earthflows of sizes unequaled in historical time while radiocarbon ages of 15 landslides as much as 35 km apart range from ca 1870 to 5130 yr b p the majority of events cluster at ca 4550 yr b p the coincidence of numerous large failures in different paleovalleys occurring concurrently long after channel abandonment and at a time of drier climate suggests that the widespread landsliding was triggered by a strong earthquake close to the landslide area areas of very disturbed terrain in a flat erosional plain show severely deformed bedding and irregular ground subsidence and are attributed to a large earthquake ca 7060 yr b p that strongly shook a thick sequence of sensitive material filling deep steep sided bedrock basins

depth determination of north italian earthquakes using grafenberg data surface reflections such as pp and sp have long been used to determine the source depth of teleseismic events due to difficulties in identifying these phases at single narrow band stations they have rarely been used for regional events correlation over an array of stations and the possibility of applying different filters to broadband data allows such phases to be identified we describe a method to determine the source depth which uses such depth phases at regional distances complete theoretical seismograms are an important aid for the interpretation of these depth phases the method is demonstrated using small events from the lombardia region and large events from friuli northern italy good agreement is achieved with depth determinations by other authors for the friuli events relative source depths are determined very accurately since only time differences need to be compared

soil erosion via preferential flow to drainage systems in clay soils runoff measurements from artificially levelled land showed that rates of particle erosion to the drainage system was even higher than that from surface runoff this effect was increased by tillage whilst no tillage reduced the losses significantly the field site soil type was a silty clay loam artificial levelling at the site had exposed an unstable subsoil susceptible to cracking soil structures with macropores and cracks were examined to find out more about water and particle transport via preferential flow pathways a field profile description of soil structure and ct scanning of monoliths from the plough layer subsoil and backfill showed different density patterns and structural properties the backfill consisted of clods and open voids with direct contact to the drainpipes the soil down to 50 cm was cracked both vertically and horizontally and some cracks were leading into the backfill cracks of up to 10 mm width were found indicating that transport of particles through them was possible the measured field hydraulic conductivities varied over 3 orders of magnitude indicative of a preferential flow network infiltration with dye tracer visually demonstrated rapid flow of water through cracks leading directly to the drainage system with a hydraulic conductivity of 9 9 10 4 m s 1 in the soil and 5 8 10 3 m s 1 in the backfill these results indicate that particles can be eroded from the plough layer and transported both laterally and vertically through macropores and cracks into the backfill and then directly to drain pipes

circum arctic petroleum potential more than 30 sedimentary basins surround the arctic ocean a reconstruction of the ancient structural depositional and climatic trends has been made of the more important basins to evaluate the relative hydrocarbon potential of this frontier area although tectonic movement has been active throughout the phanerozoic four periods of tectonism were of particular importance in forming and developing the arctic basins the caledonian orogeny during the devonian the formation of the ural mountains during the permian triassic collision of the siberian and baltic platforms the opening of the canada deep during the late jurassic early cretaceous and sea floor spreading along the nansen gakkel ridge during the early tertiary these events created a complex paleoenvironmental history for the arctic basins resulting in a variety of sources seals and reservoirs end page 101

comments about the age of the canada basin abstract the canada basin appears to have formed over a 60 ma interval during the cretaceous period the opening process can be divided into two parts continental breakup widespread in hauterivian through aptian time about 113 131 ma ago along what was about to become the polar margin of north america and seafloor formation active during the extended cretaceous interval of normal geomagnetic polarity to marine magnetic anomaly 33 time about 118 79 ma ago presently available age controls indicate that all parts of the north american polar margin could have formed at about the same time two styles of margin formation are evident from brock to axel heiberg island there appears to be an extended 70 ma stratigraphic hiatus and northeastward from ellef ringnes island extensive tholeiitic igneous activity associated with continental breakup from banks island to northeastern alaska the breakup interval is abbreviated 20 30 ma and few igneous rocks are observed a progressive difference may be indicated in the amount and or rate of crustal stretching during margin formation with relatively less slower stretching having occurred along the segment southwest of brock island and relatively more faster stretching having taken place along the segment to the northeast

calibration of the regional crustal waveguide and the retrieval of source parameters using waveform modeling regional crustal waveguide calibration is essential to the retrieval of source parameters and the location of smaller m 4 8 seismic events this path calibration of regional seismic phases is strongly dependent on the accuracy of hypocentral locations of calibration or master events this information can be difficult to obtain especially for smaller events generally explosion or quarry blast generated travel time data with known locations and origin times are useful for developing the path calibration parameters but in many regions such data sets are scanty or do not exist we present a method which is useful for regional path calibration independent of such data i e with earthquakes which is applicable for events down to m w 4 and which has successfully been applied in india central asia western mediterranean north africa tibet and the former soviet union these studies suggest that reliably determining depth is essential to establishing accurate epicentral location and origin time for events we find that the error in source depth does not necessarily trade off only with the origin time for events with poor azimuthal coverage but with the horizontal location as well thus resulting in poor epicentral locations for example hypocenters for some events in central asia were found to move from their fixed depth locations by about 20 km such errors in location and depth will propagate into path calibration parameters particularly with respect to travel times the modeling of teleseismic depth phases pp sp yields accurate depths for earthquakes down to magnitude m w 4 7 this m w threshold can be lowered to four if regional seismograms are used in conjunction with a calibrated velocity structure model to determine depth with the relative amplitude of the p nl waves to the surface waves and the interaction of regional spmp and ppmp phases being good indicators of event depths we also found that for deep events a seismic phase which follows an s wave path to the surface and becomes critical developing a head wave by s to p conversion is also indicative of depth the detailed characteristic of this phase is controlled by the crustal waveguide the key to calibrating regionalized crustal velocity structure is to determine depths for a set of master events by applying the above methods and then by modeling characteristic features that are recorded on the regional waveforms the regionalization scheme can also incorporate mixed path crustal waveguide models for cases in which seismic waves traverse two or more distinctly different crustal structures we also demonstrate that once depths are established we need only two stations travel time data to obtain reliable epicentral locations using a new adaptive grid search technique which yields locations similar to those determined using travel time data from local seismic networks with better azimuthal coverage

soil loosening and drainage of structurally unstable silty soils abstract secondary drainage treatments are carried out with the objective of enhancing the performance of permanent piped schemes in this study a drainage experiment was designed to investigate the effect of soil loosening on storm water redistribution in a structurally unstable silt soil following the installation of underdrainage results show that even though loosening reduced dry bulk density between 0 2 and 0 4 m depth by 15 with a 270 increase in transmission pores 60 m equivalent diameter at the interface of what was the cultivated and undisturbed soil drainage efficiency was not enhanced as might have been expected from the 10 to 20 fold increase in hydraulic conductivity loosening not only lengthens the median time of concentration by 0 42 and 0 33 h for simple and secondary winter storms respectively but also caused lower peak discharges when compared with unloosened soil measurements of soil water energetics reveal that a greater proportion of rainfall is diverted into the loosened zone below the plough layer and detained there reducing the 24 h drainage efficiency on a seasonal timescale the greater storage between 0 2 and 0 4 m depth causes a 6 3 increase in the winter mean water content and means that the rooting environment of the loosened soil is wetter prior to a rainstorm consequently in wet autumns and springs loosened soils will be more susceptible to structural damage by animal poaching or the traffic of farm machinery

transform margin of the northern levant eastern mediterranean from formation to reactivation 1 the levant continental margin eastern mediterranean is usually defined as a passive margin that developed between the late paleozoic early mid mesozoic previous studies suggest that the margin is composed of two segments with different structural characteristics the southern segment south of the carmel structure was formed by rifting whereas the origin of the northern segment is not known the present study focuses on the northern segment which is a key for understanding the tectonic history of the eastern mediterranean investigation is carried out offshore on two scales 1 deep crustal observations analysis of seismic refraction and magnetic data and their comparison with other continental margins worldwide and 2 shallow crustal scale observations of recent tectonic deformations based on multichannel and single channel seismic reflection profiles integration of the deep and shallow observations with reevaluation of geological data onland show strong structural resemblance between the northern levant segment and other transform margins a modified scenario is suggested for the formation and development of the levant basin and its margins combining all previous studies into one simple picture where a signature of older structures on more recent features is evident located in the midst of the progressive afro eurasian collision the northern levant presents a unique lifecycle for transform margins worldwide from formation to reactivation

earthquake source parameters and state of stress for the northeastern united states and southeastern canada from analysis of regional seismograms we examine 16 moderate size earthquakes that have occurred since 1990 in the northeastern united states and southeastern canada source parameters such as focal mechanism focal depth and seismic moment are determined using a regional waveform inversion technique in which the best fitting double couple mechanism is obtained through a grid search over strike dip and rake angles most of the 16 events and 10 previous ones with well determined focal mechanisms show horizontal compression with near horizontal p axes striking northeasterly which is consistent with the maximum horizontal stress orientation for midplate north america four shocks along the st lawrence river however have p axes trending southeast 100 130 which is not compatible with the regional stress field and requires a local stress perturbation close to the st lawrence river we examine several generating mechanisms for this localized stress variation including that a rift pillow structure may exist in the lower crust below the st lawrence river all of the 11 shocks in the united states occurred at shallow depths from 2 to 8 km the 15 canadian events are systematically deeper with foci between 5 and 28 km this geographic variation in focal depth is well correlated with the difference in surface heat flow values between the older grenville and younger appalachian provinces in the study area we also examine apparent discrepancies between m w and m b lg magnitude for 17 events five earthquakes of very similar m w show variations in m b lg as large as 0 6 which implies that for seismic events with similar seismic moment in the study area high frequency seismic radiation behavior differs considerably manuscript received 23 october 2002

forward waveform modelling procedure for 1 d crustal velocity structure and its application to the southern korean peninsula summary we propose a full grid search procedure for broad band waveform modelling to determine a 1 d crustal velocity model the velocity model can be more constrained because of the use of broad band waveforms instead of traveltimes for the crustal phases although only a small number of event station pairs were employed despite the time consuming nature of the full grid search method to search the whole model parameter space the use of an empirical relationship between the p and s wave velocities can significantly reduce computation time the proposed method was applied to a case in the southern korean peninsula broad band waveforms obtained from two inland earthquakes that occurred on 2007 january 20 mw 4 6 and 2004 april 26 mw 3 6 were used to test the method the three layers over half space crustal velocity model of the p and s wave velocities was estimated comparisons of waveform fitness between the final model and previously published models demonstrate advancements in the average value of waveform fitness for the inland earthquakes in addition 1 d velocity models were determined for three distinct tectonic regions namely the gyonggi massif the okcheon belt and the gyeongsang basin which are all located inside the study area a comparison between the three models demonstrates that the crustal thickness of the southern korean peninsula increases from nw to se and that the lower crustal composition of the okcheon belt differs from that of the other tectonic regions

water movement and soil swelling in a dry cracked vertisol abstract vertisols are widely used for irrigated rice in the senegal river basin where farmers are increasingly reporting problems with soil salinization water movement at the onset of the growing season when soils are dry and cracked may have a large impact on soil salinity and water economy water movement and soil swelling processes were studied in a dry cracked vertisol in the senegal river valley surface irrigation and simulated rainfall intensity 88 mm h 1 on cracked 2 25 m 2 plots crack width 0 01 0 02 m crack depth 0 3 m resulted in crack closure within 4 5 h starting at the soil surface soil swelling was separated into two components 1 swelling of the 0 01 0 02 m border zone of a soil island soil mass distinctively separated by cracks and 2 swelling of the rest of the soil island as a whole soil swelling was heterogeneous with a very rapid expansion of the border zone at the moment of crack closure the relative contributions of these two components to crack closure were respectively 80 90 and 10 20 24 h later these percentages changed slightly only maximum bulk linear shrinkage determined at the field level was only 7 results indicate the importance of rapid local heterogeneous swelling processes to water flow into cracked vertisol resulting in limited bypass flow use of bulk shrinkage curves and assumptions on isotropy of shrinkage and swelling processes when modelling water and solute flow in cracked vertisols should therefore be done with great care

rupture directivity of the 18 april 2008 mt carmel illinois earthquake from modeling of local seismic waveforms the 2008 m w 5 2 mt carmel earthquake is the largest earthquake in the last 50 yrs in southeastern illinois near the north termination of the north northeast trending wabash valley fault system wvfs the earthquake shows almost pure strike slip focal mechanism but it is still uncertain which nodal plane np is the ruptured fault plane to resolve the fault plane we determine rupture directivity of the earthquake via the relative centroid method we begin with inverting the point source solution strike 297 dip 84 rake 1 for np1 strike 206 dip 89 rake 173 for np2 and centroid depth 16 km and then determine the relative location between the centroid and hypocenter via regional waveform fitting two m 4 aftershocks are used as reference events and the waveform time shifts of reference events with respect to the 1d velocity model are used to calibrate the path effects the results show that the illinois mainshock ruptured to east southeast along the 297 np for about 2 3 km consistent with relocated aftershock distribution and we infer that the sinistral causative fault connects the north northwest trending la salle anticlinal belt and the north northeast trending wvfs

a deep seismic transect from hovgard ridge to northwestern svalbard across the continental ocean transition a sheared margin study new seismic refraction data were collected across the western svalbard continental marginoff kongsfjorden ny lesund during the cruise leg ark15 2 of rv polarstern the use ofon and offshore seismic receivers and a dense airgun shot pattern provide a detailed viewof the velocity structure of svalbardos continental interior the continent ocean transition and oceanic crust related to the northern knipovich ridge and the molloy ridge the caledonian central and western terranes of svalbard are not distinguishable on the basisof seismic velocity structure below a 7 to 8 km thick paleozoic sedimentary cover the crystallinecrust reveals a three layer structure with seismic velocities ranging between 6 1 and 6 9 km s the geological suture between the terranes is imperceptible the middle and upper crust belowthe tertiary forlandsundet graben shows striking low velocities this can be related to theearly paleozoic convergent transpressive movements between svalbard and northern greenland followed by an extensional relaxing phase we argue that a brittle fractured rock formation ispresent below the graben which also buries a sedimentary paleozoic core the continent ocean transition can be classified as a sheared margin formed at the continentalpart of the spitsbergen fracture zone moderate crustal thinning is achieved only to the westof the low velocity zone below the forlandsundet graben this leads to the assumption thattranstensional rift movements since oligocene were decoupled from the central terraneof svalbard the moho dips with an angle of 45 eastwards at the continent ocean transitionthat exhibits higher seismic velocities of 7 2 km s on the continental side these can beinterpreted as minor mantle derived intrusions probably induced by convection due to thejuxtaposition of cool continental and hot oceanic lithosphere the oceanic crust generated at the knipovich ridge and the molloy ridge is thin 2 to 4 km compared to the global mean and is characterised by the absence of oceanic layer 3 theseobservations can be ascribed to conductive cooling of the ascending mantle due to theextremely low divergence rate and the neighbouring cool continental crust the underlyingmantle is slightly serpentinized below the knipovich ridge segment reflected by low seismicvelocities of 7 7 km s a thicker sequence of syn and post rift sediments and sedimentaryrocks are observed on the molloy ridge oceanic segment which results from greater subsidencerelative to the knipovich ridge segment

evolution and regional stratigraphy of the northeastern canadian polar margin seismic refraction data from the northeastern canadian polar margin were compared to sonic logs and other refraction data in the area to develop a regional stratigraphy for the continental shelf north of the sverdrup rim a schematic geological cross section derived from these data showed 12 km of sedimentary rocks north of the rim based on seismic correlations the section near the edge of the shelf was predicted to consist of 4 km of upper cretaceous to tertiary postrift strata with an initial velocity of 2 1 km s 1 and a high gradient of 0 5 s overlying about 8 km of lower mesozoic to palaeozoic synrift strata with an initial velocity of 4 4 km s 1 and a lower gradient of 0 1 0 15 s all resting on a crystalline basement with a velocity of about 6 2 km s 1 mantle was measured at a depth of 25 km on the outer shelf the geological interpretation of the margin was examined in terms of circum arctic geology and was shown to be consistent with it when the arctic ocean was reconstructed to its predrift position during mississippian to early cretaceous the close spatial relationship of the canadian polar margin basin to the brooks mackenzie basin of alaska which has a mississippian to hauterivian sequence supported the geological interpretation of the margin described here

biophysical effects on soil crack morphology in a faunally active dryland vertisol abstract faunal behavior in dryland ecosystems may physically influence swelling soil hydrologic and pedologic processes due to its contributions to soil crack formation in order to provide a physical link between this faunal activity and pedological processes we use a resin visualization technique and x ray imaging to characterize the biomechanical influences of biocompaction mega meso herbivores and bioturbation termites on 3d crack morphology and topology in a faunally active dryland vertisol system results show increased soil cracking intensity due to faunal influence however this increased cracking diverged by faunal influence bioturbation creates surficial shallow extensive crack networks while biocompaction creates systematic deep narrow crack networks compared to a reference soil biocompacted soils also exhibit a memory of past wetting and drying events via vertically layered crack morphologies despite differences in these crack magnitudes between the faunal influences crack structures show morphological and topological similarity as a topological network these persistent differences in field crack systems may potentially create convectively driven hotspots of enhanced water and carbon gas transport in dryland ecosystems as a result of crack formation highlighting the importance of considering fracture behavior in both an ecological atmospheric and pedologic context

depth of faulting during the 1968 meckering australia earthquake sequence determined from waveform analysis of local seismograms waveforms for 11 foreshocks and 48 aftershocks of the ms 6 8 meckering earthquake recorded at the world wide standard seismograph network station mundaring are analyzed to determine the depth distribtion of faulting during this unusual intraplate earthquake sequence clear depth phases including sp and rg are seen in the local seismograms at distances of 60 95 km and are studied using synthetic seismograms computed using generalized ray theory and wave number integration techniques large rg s ratios seen on the vertical component short period data for many events imply source depths less than 2 km the short period p waveform contains the best depth estimator in the form of sp so that depth can be estimated to within an uncertainty of about 1 km for most events the foreshocks cluster at less than 2 km depth and most aftershocks occur within 1 km of the surface a few aftershocks occur as deep as 7 km these results are consistent with a previous teleseismic waveform study in which faulting was inferred to start near the surface at 1 5 km depth with rupture proceeding downward and not exceeding 6 km depth these results coupled with previous stress studies in the australian shield and models of crustal strength show that faulting in a cold shield area is a near surface phenomenon and implies that most of the crust is too strong to be fractured

variations in the hydrology of an underdrained clay hillslope abstract this paper presents evidence for the existence of the hydrological routes by which rainfall moves to the drainage system through clay soil at wytham in oxfordshire uk focusing particularly on the hydrology of the a horizon tile drain discharge was continuously monitored at the site and piezometer and tensiometer arrays were installed over the hillslope in order to study the spatial variations in hydrological response to rainfall a combination of dye tracing ring and tension infiltrometry was used to determine the variations in infiltration capacity over the hillslope and to characterise macropore flow the study established that both lateral and vertical macropore flow through inter pedal cracks are an important component of the hydrology of an underdrained site two regions of macropore discontinuity were identified in the soil profile at the base of the rotovated layer and at the base of the a horizon saturated layers developed at both these locations during rainfall over the winter a surface seal developed at the base of the hillslope tension infiltrometer measurements suggested that once the soil surface was sealed earthworm burrows of 6 mm diameter were responsible for up to 86 of the vertical infiltration into the a horizon temporal variations in hydrological characteristics were noted due to the swelling of the clay soil as it wetted up during the autumn and winter period lateral flow took place by a combination of macropore and preferential routes in saturated regions within the a horizon during periods of winter drainflow lateral macropore flow in the top 10 cm of the soil was the most important lateral route for water and was initiated by a critical pore water pressure of 0 3 kpa deeper lateral flow was limited and occurred predominantly through the soil matrix during autumn drainflow however inter pedal cracks were well developed through the a horizon and lateral flow at the base of the a horizon was dominant

source estimation from broadband regional seismograms recently developed source inversion techniques do not take full advantage of the broadband nature of regional seismograms the reason is that green s functions generated from flat layered models are not correct for the complicated propagational phenomena associated with realistic crustal structure the inversion is usually performed by removing short periods and inverting only selected portions of the records in this article we introduce a source estimation technique that allows for better use of the entire broadband record when only imperfect green s function are available the procedure desensitizes the timing between the principal crustal arrivals by fitting portions of the green s functions independently the preferred source is the orientation that minimizes the average l1 and l2 norms in term of the four parameters m 0 strike dip and rake the l2 error emphasizes the longer period surface waves while the l1 error weights the shorter period body waves we obtain estimates of duration by modeling long period and broadband signals the depth determination can be obtained directly from the surface reflected phases sp mp or ss ms or by cycling through the depth dependent green s functions in addition to the source parameters we obtain t phase alignments shifts that can be used as green s function corrections for relocating other events or as a guide to deriving new crustal models

the movement of water through cores of a dry cracked clay loam grassland topsoil abstract water bypassed the soil matrix through cracks and other large voids when applied to cores of dry cracked clay loam grassland topsoil at rates in excess of 2 2 mm hr 1 the bypassing ratio increased from 0 to 0 55 as the application rate rose from 2 2 to 21 2 mm hr 1 it was estimated that 10 20 of rainfall bypassed the top 0 09 m of a grassland soil at wytham near oxford england during periods of summer soil moisture deficit

constraints on crust mantle transition zone with pn waveforms a case study of eastern china and southern korean peninsula abstract the seismic velocity structure of the crust mantle transition zone cmtz provides key constraints on crustal dynamics and can be studied with pn wave which propagates horizontally along the moho discontinuity in this study we first explore an effect of velocity gradient structures in the cmtz through synthetic pn waveforms and demonstrate that the shape of pn changes from step like to pulse like when the cmtz becomes from sharp to a gradient velocity structure respectively we then use pn waveforms of the regional earthquakes the july 2012 mw 4 8 earthquake in east china and the september 2016 mw 5 1 earthquake in south korea to examine the cmtz structures to the west and east of the yellow sea and thus to constrain tectonic affinity between the eastern china and southern korean peninsula the pn waveforms from the mw 4 8 event in east china show that the moho in southern yangtze craton is sharp whereas there may be a gradient structure in cmtz with a 6 10 km thickness in northern yangtze craton the pn waveforms from the mw 5 1 event in south korea show that the cmtz in south korea is also sharp similar to the southern yangtze craton observed difference in cmtz structures suggest that sulu orogenic belt may extend along the north of the gyeonggi massif in korea

focal depths for small to moderate earthquakes mn 2 8 in western quebec southern ontario and northern new york regional depth phase modeling is a useful technique to constrain earthquake focal depths for events within sparse networks we demonstrate how regional depth phases can be used to obtain focal depths for hundreds of earthquakes with m n 2 8 that occurred from 1980 to 2004 in southern ontario western quebec and northern new york state we discuss the development of regional depth phases with distance their use in focal depth determinations by matching waveforms to synthetics and possible sources of error in general focal depths can be determined to within about 3 km when there is at least one record at regional distances with clearly identifiable depth phases such as spmp or spg in southwestern ontario and northern new york focal depths range from 2 to 15 km in areas of western quebec and along the ottawa river valley in ontario focal depths range from 2 to 25 km more than half of the earthquakes in a cluster of activity near maniwaki in western quebec are deeper than 20 km all earthquakes deeper than 20 km occurred north of about 45 3 n there is an intriguing tendency for earthquake depths to cluster near 8 km 12 km 15 km and 22 km another interesting observation is that there are several earthquake pairs or small groups with very similar epicenters but quite different depths the most active regions in western quebec and along the ottawa river valley tend to exhibit a relatively wide range of focal depths along broad zones that trend roughly northwest suggesting that seismicity is occurring along diffuse northwest trending faults throughout the crust the wide range of focal depths may indicate the potential for a larger maximum scale of fault rupture and serve as a contemporary marker of locations where large events have occurred in the recent geologic past

preferential flow paths in a water repellent clay soil with grass cover grass covered heavy basin clay soils in the netherlands appeared to be water repellent water repellency in the top layers of these soils occurred mainly as a coating on the aggregates the variation in soil moisture content over short distances was studied by sampling the soil 10 times during the period august 31 1993 to december 22 1994 each time 35 samples 100 cm3 were taken in close order over a distance of 195 cm at depths of 0 5 10 15 20 25 and 30 35 cm differences between minimum and maximum soil moisture contents were high in all layers sampled occasionally as much as 28 vol when the clay soil is dry a major proportion of the water from precipitation or sprinkler irrigation may flow rapidly through shrinkage cracks to the subsoil bypassing the matrix of the clay peds however preferential flow is not limited to macropore flow irregular wetting patterns are also formed through the small pores of the matrix the relationship between dry bulk density and volumetric water content was found to be positive when the clay soil was relatively dry and negative when it was relatively wet

modeling multidomain hydraulic properties of shrink swell soils shrink swell soils crack and become compacted as they dry changing properties such as bulk density and hydraulic conductivity multidomain models divide soil into independent realms that allow soil cracks to be incorporated into classical flow and transport models incongruously most applications of multidomain models assume that the porosity distributions bulk density and effective saturated hydraulic conductivity of the soil are constant this study builds on a recently derived soil shrinkage model to develop a new multidomain dual permeability model that can accurately predict variations in soil hydraulic properties due to dynamic changes in crack size and connectivity the model only requires estimates of soil gravimetric water content and a minimal set of parameters all of which can be determined using laboratory and or field measurements we apply the model to eight clayey soils and demonstrate its ability to quantify variations in volumetric water content as can be determined during measurement of a soil water characteristic curve and transient saturated hydraulic conductivity ks as can be measured using infiltration tests the proposed model is able to capture observed variations in ks of one to more than two orders of magnitude in contrast other dual permeability models assume that ks is constant resulting in the potential for large error when predicting water movement through shrink swell soils overall the multidomain model presented here successfully quantifies fluctuations in the hydraulic properties of shrink swell soil matrices and are suitable for use in physical flow and transport models based on darcy s law the richards equation and the advection dispersion equation

regional waveform calibration in the pamir hindu kush region twelve moderate magnitude earthquakes m b 4 5 5 in the pamir hindu kush region are investigated to determine their focal mechanisms and to relocate them using their regional waveform records at two broadband arrays the kyrgyzstan regional network knet and the 1992 pakistan himalayas seismic experiment array pakh in northern pakistan we use the cut and paste source estimation technique to invert the whole broadband waveforms for mechanisms and depths assuming a one dimensional velocity model developed for the adjacent tibetan plateau for several large events the source mechanisms obtained agree with those available from the harvard centroid moment tensor cmt solutions an advantage of using regional broadband waveforms is that focal depths can be better constrained either from amplitude ratios of pnl to surface waves for crustal events or from time separation between the direct p and the shear coupled p wave spn spmp for mantle events all the crustal events are relocated at shallower depths compared with their international seismological centre bulletin or harvard cmt depths after the focal depths are established the events are then relocated horizontally using their first arrival times only minor offsets in epicentral location are found for all mantle events and the bigger crustal events while rather large offsets up to 30 km occur for the smaller crustal events we also tested the performance of waveform inversion using only two broadband stations one from the knet array in the north of the region and one from the pakh array in the south we found that this geometry is adequate for determining focal depths and mechanisms of moderate size earthquakes in the pamir hindu kush region

focal depth distribution of the 1982 miramichi earthquake sequence determined by modelling depth phases on 9 january 1982 in the miramichi region of new brunswick canada an earthquake with body wave magnitude mb 5 7 occurred and extensive aftershocks followed the mainshock was felt throughout eastern canada and new england usa the mainshock and several principal aftershocks were digitally recorded worldwide but smaller aftershocks were digitally recorded only at regional stations digital stations were not yet popular in 1982 therefore available regional digital waveform records for modelling are very limited fortunately two eastern canada telemetered network ectn stations ebn and kln produced excellent waveform records for most of the aftershocks until their closure at the end of 1990 the waveform records can be retrieved from the archive database at the geological survey of canada gsc since ebn had clear spmp records of the larger aftershocks with magnitude mn 2 8 we were able to determine focal depths for these larger events most of the focal depth solutions for the 113 larger

source retrieval from broadband regional seismograms hindu kush region abstract a method of relocation and source characterization of small earthquakes using one modern regional station is developed and tested first we model teleseismic body waves of two events which are used as masters short period depth phases pp and sp are used to establish the epicentral depth and the events are relocated using calibrated stations and a mantle model derived for this region tip the events moved upward by 12 and 31 km respectively the regional waveforms recorded at the iris station gar from the best determined source are forward modeled to establish a local crustal model a four layered model with a thickness of 65 km proves effective synthetics from this crustal model can then be compared with the data from other events where the depths are poorly known i e pde depths of 33 km forward modeling of the short period phases allows better estimates of depth and makes relocation possible next we perform a long period inversion of whole and partial waveform data to obtain source mechanism and moment and repeat the procedure if necessary this technique is applied to events in the tectonically active pamir hindu kush region to test its usefulness five crustal events sampling various azimuths are presented as examples of relocation and determination of source mechanisms from small events the smallest event has a moment of 5 1 1022 dyn cm for the seven events we studied the average depth correction to pde is 19 km and the location correction is 11 km on average the method can be used to identify earthquakes and thus it lowers the threshold below present mb ms discrimination since these events are too small to be seen teleseismically secondly these events can be used as masters in the calibration of other systems case based event characterizations etc

green ampt infiltration model for sloping surfaces 1 this work quantifies and explains the direct physical effects of slope angle on infiltration and runoff generation by extending the green ampt equation onto sloping surfaces a new extended solution using identical precipitation hydrographs was compared to the original formulation and then used to calculate the infiltration and runoff generation for different slope angles but for identical horizontal projection lengths homogeneous and isotropic soil is assumed and two different boundary conditions for vertical rainfall are studied ponded infiltration and infiltration under steady rainfall infiltration under unsteady rainfall was found to be similar to cases with steady rainfall both theoretical and numerical results show that infiltration increases with increasing slope angle for cases with ponded infiltration the slope effect was generally not significant for mild to moderate slopes but the slope effect became more important for low intensity and short duration rainfall events especially as it delayed the time for ponding it was also found that the cumulative vertical infiltration depth ihp at ponding or the initial loss increases with increasing slope angle the model was compared to richards equation on horizontal and sloping surfaces and found to perform well the model s applicability for nonuniform slopes was discussed and it was found that the model is generally applicable for isotropic and mildly anisotropic soils except for some small scale topographic elements finally the occurrence of nonvertical rainfall could increase runoff with increasing slope angle when rainfall deflects a large angle to upslope

earthquake source mechanism and rupture directivity of the 12 september 2016 mw 5 5 gyeongju south korea earthquakeshort note

focal depth determination for moderate and small earthquakes by modeling regional depth phases spg spmp and spn there are three usable regional depth phases spg spmp and spn and their corresponding reference phases pg pmp and pn the differential time between each depth phase and its reference phase can be used to estimate earthquake focal depth we have developed a method to determine focal depth for moderate and small earthquakes by using a regional depth phase modeling rdpm method we used a default focal mechanism to generate the differential times for all earthquakes to estimate the reliability of the modeled focal depths we compared our solutions with those obtained by other methods and found the consistency is good because the focal depths estimated by rdpm are model dependent we tested the extent of the dependency and found that a 10 error in the crustal model may generate a 10 15 error in the modeled depth the absolute error is determined by the error in the crustal model and the focal depth itself we found that earthquake location errors have only a small effect on the modeled focal depths by analyzing synthetic and observed waveforms we found a distance window within which spmp and pmp are well developed and within the window the p portion of the waveform is relatively simple and spmp and pmp are easy to identify we also demonstrated that the assumptions of spmp and pmp are correct that regional depth phases are not developed or not discernible in some regions and that regional depth phases have special features that can be used to identify those phases

the sspmp phase in regional wave propagation abstract regional broadband waveforms of deep and intermediate depth earthquakes written at college alaska and matsushiro japan show large sspmp phases that may be the largest phase seen on the seismogram sspmp is created when the direct upgoing sv wave converts to a p wave at the free surface and subsequently becomes trapped in the crust because of postcritical p wave reflection at the moho sspmp may arrive between the p and s wave phases or it may arrive after s depending on source depth and distance thus it can be used as an additional constraint on source depth and location it is important to recognize the existence of this phase since it is easily confused with the s wave arrival resulting in erroneous s wave arrival time picks or it may be interpreted as a split shear wave incorrectly implying shear wave anisotropy in the medium such a wave propagation effect will also be important for a crustal source for structures that contain low velocity layers near the surface

the 1982 cocrust seismic experiment across the ottawa bonnechere graben and grenville front in ontario and quebec summary during the summer of 1982 the canadian consortium for crustal reconnaissance using seismic techniques cocrust conducted a major long range seismic refraction and wide angle reflection experiment across the grenville province of the canadian shield three seismic lines each approximately 300 km in length were located i along the ottawa bonnechere graben ii perpendicular to the graben and iii perpendicular to the crenville front geological evidence indicates that the graben may have originated from a failed arm of the st lawrence rift system and the grenville front marks the boundary between the grenville province and the much older superior province other geological features of the grenville province that were traversed by the profiles were the central metasedimentary belt and the central gneiss belt analysis of the data involved conventional traveltime procedures coupled with the use of synthetic seismogram analysis using programs that were written to handle laterally heterogeneous structures results from the survey indicate a variation in near surface seismic velocity

active tectonic studies in the united states 1987 1990 the techniques and instrumentation used in active tectonic studies are discussed and recent results are reviewed it is suggested that a critical mass of data on several particular regions has been accumulated making possible critical debates and attempts to assess earthquake hazards particular attention is given to studies of the pacific northwest region basin and range deformation studies and distributed deformation and hidden earthquake sources also included is a comprehensive bibliography for the period

water movement and isoproturon behaviour in a drained heavy clay soil 1 preferential flow processes abstract the processes and mechanisms that control pesticide transport from drained heavy clay catchments are being studied at wytham farm oxford university in southern england in the first field season field drain water contained high concentrations of pesticide soil studies demonstrated that the main mechanism for pesticide translocation was by preferential flow processes both over the soil surface and through the soil profile via a macropore system that effectively by passed the soil matrix this macropore system included worm holes shrinkage cracks and cracks resulting from ploughing rainfall events in early winter rapidly created a layer of saturation in the a horizon perched above a b horizon of very low hydraulic conductivity drain flow was initiated when the saturated layer in the a horizon extended into the upper 0 06m of the soil profile thereafter water moved down slope via horizontal macropores possibly through a band of incorporated straw residues these horizontal pathways for water movement connected with the fracture system of the mole drains thus feeding the drains overland flow occurred infrequently during the season

am improved source mechanism for the 1935 timiskaming quebec earthquake from regional waveforms the timiskaming earthquake which occurred near the quebec ontario border at the northwest end of the western quebec seismic zone in 1935 is one of the five largest instrumentally recorded southeastern canadian earthquakes previous studies of this earthquake concentrated on modeling teismograms recorded at regional distances a better constrained focal mechanism is obtained the waveforms indicate thrust faulting on a moderately dipping northwest striking plane at a depth of 10 km them w of 6 1 determined in this study is in good agreement with previous magnitude estimates m b 6 1 m s 6 0 andm blg 6 2 6 3 the focal mechanism is similar to those of many recent small to moderate earthquakes in the region and the inferred from thep axis acting stress of northeast compression is consistent with the overall eastern north american stress field the lake timiskaming rift valley in which the earthquake occurred comprises several northwest striking faults consistent with the strike of the 1935 event thus the 1935 earthquake appears to be a result of faulting on the reactivated timiskaming graben

shallow and deep crustal structure of the western sverdrup basin arctic canada an analysis of gravity data along two detailed profiles over the western sverdrup basin in the canadian arctic supports a seismic refraction model drill holes as deep as 5 4 km near the profiles provide excellent density control mean densities in the thickest part of the basin exceed those in the thinner parts by an average of 0 13 mg m3 bouguer anomalies corrected for the effect of water sedimentary and crystalline layers indicate significant anomalies that vary in width from 20 to 275 km and in amplitude from 3 to 46 mgal 30 to 460 m s 2 these can all be explained by density structures within the sedimentary column sedimentary thickness along the profiles varies from 9 to 17 4 km crystalline thickness varies from 18 to 33 km and the total crustal thickness varies from 34 to 42 km the analysis also shows 1 negative gravity effects of about 60 to 120 mgal 600 to 1200 m s 2 due to the mass deficiency of the water and sediments are offset by positive gravity effects of similar magnitude du

monitoring the transition from preferential to matrix flow in cracking clay soil through changes in electrical anisotropy abstract transition from preferential flow to matrix flow in a vertisol was investigated by combined use of square array resistivity measurements and stable water isotopes two irrigation events with water of different water isotope composition were carried out on a 0 5 m deep initially dry and cracked soil profile in a weighing lysimeter throughout the irrigation events depth profiles of resistivity square array measurements were collected to calculate profiles of the anisotropy index ai and mean resistivity the stable isotope composition of the drainage water showed that water from the second irrigation bypassed the soil matrix with limited mixing to form the collected drainage this bypass showed that even though the soil cracks at the surface were visually closed at the onset of the second irrigation preferential flow paths must have remained open changes of the ai with applied irrigation volume were used to detect the dominant flow processes in the soil with a stable ai indicating matrix flow and an unstable ai indicating preferential flow the ai showed that over the course of the irrigation events the dominant flow process changed from preferential flow to matrix flow the use of the ai allowed for the first time to detect the exact timing of this transition matrix dominated flow didn t occur until ponding water at the soil surface was observed the onset of matrix flow started at the top of the profile and progressed downwards complete crack closure in terms of water flow occurred long after visual closure of soil cracks and could be detected by monitoring changes in the ai

the 25 november 1988 saguenay quebec earthquake source parameters and the attenuation of strong ground motion the saguenay earthquake of 25 november 1988 occurred close to the southern margin of the saguenay graben in southern quebec it was caused by almost purely dip slip faulting centered at a depth of 26 km with a p axis oriented northeast southwest this faulting mechanism is similar to those of the larger historical earthquakes in eastern north america but the focal depth is substantially greater than all but one of these events the seismic moment estimated from regional pni waves and teleseismic long period body waves is 5 10 24 dyne cm corresponding to a moment magnitude of 5 8 the source duration of the earthquake is estimated to be 1 8 sec corresponding to a stress drop of 160 bars which is not significantly higher than the average stress drop of 120 bars estimated from previous large earthquakes in eastern north america in order to simultaneously match the recorded ground motion amplitudes of strong motion acceleration strong motion velocity and teleseismic short period and long period body waves it is necessary to use a source function having a complex shape that implies the presence of asperities and larger local stress drops the large set of strong motion recordings of the saguenay earthquake has been used to validate a procedure for estimating strong ground motion attenuation based on a simple wave propagation model the most important feature of the recorded strong motions is that their peak amplitudes do not decay significantly with distance inside 120 km but then decay abruptly beyond 120 km profiles of recorded accelerograms with absolute times indicate that at distances beyond 64 km the peak ground motions are due to strong postcritical reflections from velocity gradients in the lower crust the principal shear wave arrivals and the variation of their peak amplitudes with distance were reproduced in synthetic seismograms generated using a regional crustal structure model the critical distances for the postcritical reflections were short because of the deep focal depth of the event causing the elevation of ground motion amplitudes out to 120 km similar studies of earthquakes in other regions of eastern north america indicate that the strength of the postcritical reflections and the distance ranges over which they are dominant are controlled by the focal depth and crustal structure regional variations in crustal structure thus give rise to predictable regional variations in strong ground motion attenuation