large horizontal surface velocity shears in the ocean obtained from images of refracting swell and in situ moored current data aerial photographs showing strong refraction of swell near the northern california coastline were obtained on september 8 1982 the possibility that this refraction is due to a large horizontal current shear is discussed a maximum shear value of the order of 10 3 s 1 with the velocity directed along a linear slick like front is calculated from the wave data in the photo in situ current data obtained at 90 m depth at a nearby midshelf site on two surface moorings separated by 390 m also show occasional periods of large horizontal velocity shear on january 4 1982 a maximum horizontal shear of order 10 3 s 1 was observed for several hours these separate observations taken together indicate that large horizontal surface velocity shears of order 10 3 s 1 occur over the northern california continental shelf and that large surface current shear can be usefully detected and measured by high flying high resolution sensors

slow slip near the trench at the hikurangi subduction zone new zealand the range of fault slip behaviors near the trench at subduction plate boundaries is critical to know as this is where the world s largest most damaging tsunamis are generated our knowledge of these behaviors has remained largely incomplete partially due to the challenging nature of crustal deformation measurements at offshore plate boundaries here we present detailed seafloor deformation observations made during an offshore slow slip event sse in september and october 2014 using a network of absolute pressure gauges deployed at the hikurangi subduction margin offshore new zealand these data show the distribution of vertical seafloor deformation during the sse and reveal direct evidence for sses occurring close to the trench within 2 kilometers of the seafloor where very low temperatures and pressures exist

a case study of wave current interaction in a strong tidal current abstract during august 1991 a field program was carried out in the vicinity of cape st james off the british columbia coast where a strong tidally driven flow interacts with an active wave climate surface current maps were obtained from a codar type hf radar seasonde over an area of about 350 km2 around the cape a series of loran c drifters were also deployed during the experiment and used as ground truth for the radar a comparison between the drifter and the radar surface currents indicates reasonable agreement wave information was acquired with three waverider buoys deployed around the cape a significant modulation of the wave properties at the tidal period was observed for the buoy located in the area where the currents are maximum the tidally induced changes in the wave field are modeled with a local wave current interaction model based on wave action conservation and on a high frequency limiting spectral shape the model is applied on a period of 11 days for which the wind was relatively

an empirical relation between ocean surface wind direction and the bragg line ratio of hf radar sea echo spectra twelve days of tests with six u s air force oth b over the horizon radars produced a large surface wind direction data set covering much of the north atlantic and pacific oceans we compare wind directions derived from the sea echo bragg line ratio with concurrent in situ measurements made by ships and buoys and with the national meteorological center nmc global data assimilation system model using 1900 such comparisons we derive an empirical model for the dependence of surface wind direction on the bragg line ratio of hf radar sea echoes the rms difference between the empirical model and the combined nmc and in situ data is about 33 when only very high quality radar data are used the rms difference between the radar and buoy measurements alone is 24 the pattern of surface streamlines derived from 1 day s radar measurements over the northeastern pacific ocean closely matches that derived from the nmc model

fracture cleat analysis of coals from zonguldak basin northwestern turkey relative to the potential of coalbed methane production abstract in this study the fracture structure of three coals sulu k 1 acilik k 2 and cay dogu ayak from two different seams in the zonguldak basin located on the black sea coast of turkey have been analyzed in relation to coalbed methane recovery x ray computerized tomography ct light microscopy image analysis and scanning electron microscopy sem analysis have been performed on mine coal samples to have a better understanding of distribution of minerals fracture morphology and apertures and matrix fracture interactions via examination of fracture surfaces results show that the acilik and sulu coals seem to be structurally more prone to be commercially productive these coals show a high degree of fracturing and cleat development as evidenced by x ray ct and light microscopy examination of polished surfaces although the cay dogu ayak coal shows a high fracture density the cleat surface morphology and smaller fracture apertures may make this coal unfavorable for gas flow

southward recirculation of the east china sea kuroshio west of okinawa island 1 the surface current of the kuroshio recirculation region in the east china sea is investigated the surface currents in the west of okinawa island observed by hf radars and the assimilation results of the japan coastal ocean predictability experiment jcope are analyzed it appeared that currents in the easternmost edge of the kuroshio bifurcate southward and flow into the west of okinawa island from jcope data the currents are called kuroshio southward recirculation currents the currents are controlled by the bottom topography the wind stress curl in the area where the bifurcated current can be seen in jcope data is negative while the curl is positive in the eastern portion of the kuroshio the kuroshio southward recirculation currents are sometimes enhanced and their enhancement coincides with that of the positive and negative wind stress curls

forced ocean response during the frontal air sea interaction experiment a central hypothesis of the frontal air sea interaction experiment fasinex was that the strong gradients in the upper ocean associated with ocean fronts would spatially modulate the response of the ocean to local atmospheric forcing to test this hypothesis measurements of near surface meteorology and upper ocean variability were made for 5 months from an array of moorings and for one of those 5 months from two ships a number of fronts passed through the moored array and the moored meteorological and current meter data were used to examine the response of the upper ocean to atmospheric forcing at subinertial and near inertial frequencies at low frequencies an ekmanlike frictionally driven component in the mixed layer and a more deeply penetrating component thought to be forced by ekman pumping were found strong near inertial response was found in the mixed layer the near inertial motion showed considerable spatial variability in the seasonal thermocline here it was evident that the structure of the front influenced the downward propagating near inertial internal waves data were also obtained by profiling instruments deployed along cross frontal sections these data were used to examine the spatial and temporal variability of the internal waves microstructure and dissipation and the relation of that variability to oceanic fronts and atmospheric events the spectral densities of the components of the internal waves that rotated clockwise with increasing depth were higher in regions of negative relative vorticity than those predicted by garrett and munk munk 1981 and estimates of clockwise and total shear were highest in regions of negative relative vorticity in the strong shear of the ocean front significant anisotropy of the internal wave field was observed and kinetic energy dissipation levels relative to the rate of work by the wind were higher than previously reported

monitoring of coal mining subsidence in peri urban area of zonguldak city nw turkey with persistent scatterer interferometry using alos palsar this paper presents the results of spatiotemporal monitoring of surface subsidence over a mining area in zonguldak province of turkey using synthetic aperture radar sar data providing maps of subsidence rates in the radar line of sight direction a total of 18 sar images acquired between january 2007 and june 2010 by the japanese advanced land observing satellite have been used to map the surface displacements using the persistent scatterer interferometry technique the use of phased array type l band synthetic aperture radar data has proved useful for avoiding signal decorrelation and estimating surface deformation in the heavily vegetated study region the technique enables the monitoring of continuous small displacements over a large area our findings present that many persistent scatterers were located on the vegetation cover the results reveal areas of ground surface subsidence up to 44 mm year that are well correlated with the underground coal mining galleries particularly in the gelik region where the karadon mining galleries are present

radar backscatter across the gulf stream sea surface temperature front ku band backscatter responses to frontal sea surface temperature sst changes are studied and applications of a high resolution scatterometer to remote sensing of an sst front are suggested ocean backscatter signatures were measured with an airborne ku band scatterometer across the gulf stream sst front during the surface wave dynamics experiment oceanic and atmospheric parameters were measured by buoys by the scanning radar altimeter and by the advanced very high resolution radiometer and the surface current fields analyzed by the fleet numerical meteorology and oceanography center were obtained vertical polarization backscatter difference across the sst front with an sst difference of 9 spl deg c is more than 5 db in several flight lines large horizontal polarization backscatter changes are also observed across the sst front with an sst difference approximately one half of that in the vertical polarization backscatter case corresponding wind speed differences cannot account for the large backscatter changes in view of seasat a satellite scatterometer sass geophysical model functions depending only on neutral wind velocity for both polarizations upwind backscatter on the cold side is smaller than or close to crosswind backscatter on the warm side for incidence angles larger than 20 spl deg and smaller than 60 spl deg this suggests that the sst front can be detected with backscatter measured by a spaceborne radar at a fixed azimuth angle even if wind directions are different over the cold and warm sides

investigation on the evolution and control of surrounding rock fracture under different supporting conditions in deep roadway during excavation period abstract this paper presents an investigation of fracture evolution of surrounding rock with different supporting conditions during excavation period in hulusu coal mine inner mongolia china fractures of surrounding rock were measured by borehole images obtained with a digital panoramic borehole camera and surface displacement of roadway was measured using the intersection point method based on the rock properties original support method and constructional process of bolter miner a simple and fast support system was proposed which realized the complete parallel operation between bolt support and coal cutting according to the data obtained from field monitoring and construction situation the array pitch was extended from 1 0 m to 1 5 m gradually field measurements indicated that the overall effect of roadway under new support was more satisfactory than under original support with no exception in all the five test stages when the array pitch extended up to 1 5 m the roof and rib convergence were 11 mm and 16 mm a reduction of 66 7 and 57 9 respectively under new supporting condition fractures were distributed only within the bolt anchorage zone and both the number and opening of fractures were small by contrast under original supporting condition fractures were distributed both in and out of the bolt anchorage zone new support can make full use of deep strata by constructing thick anchorage rock beam and large displacement of shallow strata can be inhibited through small displacement of deep strata the realization of co movement between large small displacements ensures the safety control of roadway new support can greatly improve support efficiency providing a solution to the imbalance between excavation speed and production needs widely existing in coal mines producing 10 million tons a year new support has already been successful applied in another roadway with top coal in hulusu coal mine

computation of subsidence parameters resulting from layer movements post operations of underground mining abstract it is obvious to anyone working on or dealing with underground mining operations production gaps have to be opened in the ground during mining the ground layers just above these gaps collapse toward production lines resulting in horizontal and vertical movements both inside and on the earth s surface these movements are referred to as mining subsidence which eventually causes technical economic social and environmental hazards to natural and cultural structures on the surface it is substantially crucial to the general and regional characteristics of these subsidence occurrences in the underground mining region so it can be possible to mitigate the subsidence induced damages and problems both in the ground and on the surface subsidence observations thus are conducted inside and on the ground by employing geodetic geophysical and geotechnical methods with the aim to determine the characteristics and parameters of subsidence occurrence in a region evaluating these subsidence observations the zonguldak hard coal basin and kozlu coal production region within the basin are places where urbanization and underground mining operations are intensively under way therefore it is vitally important to continuously monitor the horizontal and vertical displacements formed due to the underground mining in the basin and to determine the subsidence parameters so that it may be possible to forestall the subsidence induced issues that may occur in the near future this study yields information and computations about the subsidence parameters determined under the light of three periods of geodetic observations carried out in the region using the three periods of gps and precise leveling observations the average slope angle values resulting from vertical displacements in the study region were obtained from the adjusted coordinates and height differences and estimated as 16 67 in positive direction and 18 03 in negative direction the horizontal unit deformation parameters on the other hand were computed as 0 28 mm m for the extension parameter while 0 26 mm m for compression parameter along the routes chosen in the kozlu region

a numerical study of wave current interaction through surface and bottom stresses wind driven circulation in the south atlantic bight under uniform winds the influences of surface waves on ocean currents in the coastal waters of the south atlantic bight are investigated by using a coupled wave current modeling system the ocean circulation model employed is the three dimensional princeton ocean model pom and the wave model invoked is an improved third generation wave model wam the coupling procedure between the pom and the wam and the simulated coastal ocean circulation driven by uniform surface winds are presented the simulated results show that wind waves can significantly affect coastal ocean currents not only through an enhancement of wind stress but also through a modification of bottom stress wave induced wind stress increases the magnitude of currents both at the surface and near the seabed on the other hand wave induced bottom stress weakens the currents both at the sea surface and near the seabed therefore the net effect of surface wind waves on currents depends on the relative importance of current modulations by wave induced wind stress and bottom stress the results further indicate that at a fixed location the relative importance of wave induced surface and bottom shear stresses in coastal ocean circulation depends on the surface wind field for the constant wind cases considered in this study the effect of wave induced bottom stress is more significant in along shore wind conditions than in cross shore wind conditions

hf radar comparisons with moored estimates of current speed and direction expected differences and implications the validation of estimates of ocean surface current speed and direction from high frequency hf doppler radars can be obtained through comparisons with measurements from moored near surface current meters acoustic doppler current profilers or drifters expected differences between current meter cm and hf radar estimates of ocean surface vector currents depend on numerous sources of errors and differences such as instrument and sensor limitations sampling characteristics mooring response and geophysical variability we classify these sources of errors and differences as being associated exclusively with the current meter as being associated exclusively with the hf radar or as a result of differing methodologies in which current meters and hf radars sample the spatially and temporally varying ocean surface current vector field in this latter context we consider three geophysical processes namely the stokes drift ekman drift and baroclinicity which contribute to the differences between surface and near surface vector current measurements the performance of the hf radar is evaluated on the basis of these expected differences vector currents were collected during the high resolution remote sensing experiment ii off the coast of cape hatteras north carolina in june 1993 the results of this analysis suggest that 40 60 of the observed differences between near surface cm and hf radar velocity measurements can be explained in terms of contributions from instrument noise collocation and concurrence differences and geophysical processes the rms magnitude difference ranged from 11 to 20 cm s 1 at the four mooring sites the average angular difference ranged between 15 o and 25 o of which about 10 o is attributed to the directional error of the radar current vector estimates due to the alignment of the radial beams

effects of the gulf stream on ocean waves in the present study a third generation numerical wave model is used to study effects of a straight gulf stream and a gulf stream ring on ocean waves in swell and storm conditions the model accounts for all relevant processes of propagation generation and dissipation of the waves including current effects without imposing a priori restraints on the spectral development of the waves the dominating mechanism affecting the waves appears to be current induced refraction even though the short crestedness of the incoming waves tends to mask its effects also in swell conditions depending on wind and wave conditions refraction may trap locally generated waves in the straight gulf stream or it may reflect wave energy back to the open ocean in the gulf stream ring refraction induces a considerable variation in significant wave height and short crestedness but it hardly affects the mean wave direction in storm conditions the processes of generation and dissipation are considerably enhanced in countercurrent situations and reduced following current situations

spatial variations of ocean wave directional spectra from the seasat synthetic aperture radar seasat synthetic aperture radar ocean wave spectra for a 900 km pass are analyzed and interpreted in the context of both their probable generation sources and their surface current and bathymetric modifiers systematic vector wavenumber variations of several times the standard error of determination 1 5 in magnitude and 0 9 in direction occur along the entire 900 km pass the large scale spatial variation of a 200 m swell system can be accurately accounted for as a result of dispersion from a distant storm the more local variations are qualitatively well correlated in position with known currents and bathymetry but show systematic biases that appear partly due to an environmentally dependent instrument transfer function in the regions of high current and highest sea state there is also substantial evidence that a large angular deviation in the center of the pass is the result of a mesoscale eddy just to the east

a case study of wave current interaction near an oceanic front high resolution directional wave spectrum data were obtained from two nasa airborne radars during the frontal air sea interaction experiment fasinex in february 1986 the observations show a significant change in the wave number spectrum across the front on the basis of surveys from a towed sensor and on satellite imagery the front location and current field are estimated a numerical model is developed for the wave current interaction and is used to model the wave refraction across the frontal current a parametric study is performed to demonstrate the effects of current meandering the main consequence of meandering is the formation of caustics and shadow zone regions in which the wave energy is significantly enhanced or reduced spectral simulation along the aircraft track reveals a reduction of more than 60 in wave energy in the shadow zone this is consistent with the observations

coal rank and petrography of upper carboniferous seams in the amasra coalfield turkey abstract the amasra coalfield is a part of the upper carboniferous zonguldak coal basin of turkey within the istanbul zone a hercynian deformed unit forming the eastern continuation of the moesian platform in se europe which was later deformed by alpine tectogenesis the mainly westphalian aged coals were sampled from an underground mine and from cores from nine exploration wells and petrographic maceral and microlithotype analysis and mean maximum vitrinite telocollinite reflectance r max in oil were determined the coals were characterised by low ash and low total sulphur contents abundant vitrinite group macerals and relatively abundant vitrite clarite and duroclarite microlithotypes vitrinite reflectance was in the range 0 58 1 04 r max indicating ranks from high volatile c bituminous to high volatile a bituminous coal the r max generally increases with increasing depth in the exploration wells with gradients ranging from 0 21 to 0 40 r max km and an average of 0 30 r max km the highest value occurs in the south of the coalfield in a region of hercynian folding and thrusting the relationship between vitrinite reflectance and thrusts in the wells suggests that coal rank was developed mainly pre thrusting but that some wells arguably show evidence for post thrust coalification peak coalification probably occurred during late mesozoic early tertiary rifting so that the thrusts which developed after coalification are likely to be alpine in age whereas the thrusts that pre date coalification may have been hercynian structures

wave refraction in an ocean front side looking airborne radar near cape hatteras north carolina recorded images of ocean waves wind streaks and intermediate water bodies within the gulf stream front in the enclosed waters of pamlico sound the radar images showed good accuracy in defining directions and distinguished waves from wind streaks at overlapping frequencies in the spectrum in passing through the cyclonic shear in the gulf stream front waves from both sides turned to their left and so specified their directions of propagation differences between spectra obtained across the front are in accord with current refraction theory an inverse wave refraction calculation furnished current shear values from which horizontal profiles of water velocity were compiled the total calculated velocity change of 1 5 m s is similar to previous measurements a secondary front near shore contained a velocity difference of 0 25 m s velocity changes across the gulf stream front were correlated with temperature changes the radar there showed bands of high reflectivity at the edges of intermediate water bodies whose temperature differences implied very small velocity steps increased roughness at the intermediate water boundaries was attributed to current interaction with waves

remote sensing of wind speed at sea surface level using hf skywave echoes from decametric waves using an hf skywave radar to study the decametric sea waves it appears that their amplitudes do not saturate as the wind speed increases a measurement method based on the kahma sea wave spectrum is proposed and radar estimations of the wind speed are compared with in situ measurements performed on board a ship the rms difference between the two measurements is 2 5m s and is probably mainly due to the spatial variability in the wind speed

resolving combined wave current fields from measurements using interior point optimization abstract complex wave and wave current conditions exist in the natural world and are increasingly emulated in advanced experimental facilities to de risk the deployment operation and maintenance of offshore structures and renewable energy devices this can include combinations of ocean swell multi directional wind driven seas and reflected wave conditions interacting with a current field it is vital to understand the full nature of these potentially hazardous conditions so they can be properly simulated in numerical models to contextualize measurements made in field and experimental programmes here a numerical framework is presented for isolating both the wave systems and the mean current velocities from measured data using an interior point optimizer a developed frequency domain solver is used to resolve from experimentally obtained wave gauge measurements two opposing wave systems on a collinear current and used to effectively isolate the wave systems and predict the current velocity using only wave gauge measurements thirty five test cases are considered consisting of five wave spectra interacting with seven different current velocities ranging from 0 3m s 10 3m s 1 comparisons between the theoretical and derived wave numbers and current velocities show good agreement and the performance of the method is similar to that of existing methodologies while requiring no a priori knowledge of the current velocity impacting the wave field required although results are presented for the collinear problem the presented method can be applied to a wide range of wave and current combinations and provides a useful tool for increasing understanding of both ocean and experimental conditions

tidal modulation of surface gravity waves in the gulf of maine abstractthis study examines the tidal modulation of surface gravity waves in the gulf of maine gom by using in situ observations and numerical model results analysis of observational data demons

modelling of gas generation in coals of the zonguldak basin northwestern turkey abstract the generation of gas in selected coal seams of the zonguldak basin northwestern turkey has been modelled by incorporating laboratory derived non isothermal reactions kinetics into the geothermal histories of the coal bearing strata kinetic parameters have been determined by programmed temperature open system pyrolysis of a low maturity 0 5 r 0 coal at three linnear heating rates of 0 1 0 7 and 5 0 k min the mathematical analysis of the bulk hydrocarbon evolution profiles assuming 25 first order reactions with activation energies regularly spaced between 46 and 70 kcal mol and a single pre exponential factor a yielded a value of a 3 17 10 16 min 1 and a rather broad hydrocarbon potential vs activation energy distribution with a maximum at 55 kcal mol geological time temperature relationships have been reconstructed by use of the basin modelling technique depending on the location within the basin of the wells studied and on the geological history of the coal bearing sediments the simulation procedure resulted in a predicted gas generation of up to 40 mg per g of coal

the control of coal bed decollement related slickensides on roof falls in north american late paleozoic coal basins abstract slickensides cause potentially hazardous ground conditions in underground coal mines investigations by the mine safety and health administration s msha roof control division indicate that many slickensides represent bedding plane faults and drag folds that formed during coal bed decollement a style of bedding plane faulting that occurs in shale units above coal seams these slickensides formed in response to regional tectonic stresses rather than by differential compaction and strike parallel to local and regional fold axes and thrust faults this paper relates some slickensides in the appalachian illinois arkoma and black warrior basins to the structural grain developed during the late pennsylvanian permian alleghanian orogeny provides descriptions of slickensides and advocates geologic mapping as a predictive method for identifying adverse ground conditions associated with tectonically formed slickensides

remotely sensed surface currents in monterey bay from shore based hf radar coastal ocean dynamics application radar near surface currents in monterey bay derived from a network of shore based hf radars are presented for august december 1994 and compared with those from april to september 1992 focus is placed on the low frequency 2 to 30 day period motions in the remotely sensed data and on comparison of radar derived currents with moored current and wind observations ship based acoustic doppler current profiler observations satellite based surface temperature imagery and surface drifter velocities the radar derived picture of the late summer mean flow is very similar in the two realizations and is consistent with historical data flow is equatorward in the outer part of the bay poleward in a narrow band nearshore and very sluggish in the middle of the bay low pass filtered time series of radar derived currents are highly correlated with moored current observations and with winds in the outer part of the bay the vector time series are also coherent across a broad frequency band with currents typically in phase between 1 and 9 m depths and with 1 m currents typically 40 60 to the right of the wind overall these results confirm the utility of coastal ocean dynamics applications radar codar type hf radars for the study of coastal surface currents out to ranges 50 km from shore particularly for highly averaged fields data variability and comparison with in situ observations for high frequency 1 to 48 hour period motions point to the need to better characterize and minimize sources of error in the radar observations

horizontal variability of near inertial oscillations associated with the passage of a typhoon 1 surface currents to the east of okinawa island were observed by using hf high frequency ocean radars in august september 1995 during that period a typhoon passed near the observation area and the horizontal variability of near inertial oscillations associated with the typhoon passage was estimated in addition the near inertial amplitudes and horizontal wave number vectors were estimated these estimations showed that the near inertial amplitude was large in the offshore area and small near the coast the maximum near inertial wavelength was estimated to be in the order of 1000 km and the near inertial wave direction was southward and changed to northwestward on 23 august in 1995 a slab model incorporating low frequency currents was used to calculate near inertial currents it was found that the amplitude of calculated near inertial oscillations was also large in the offshore area moreover the phase propagation direction of the near inertial waves was southward and changed to northwestward or westward on 22 august the growth rate obtained from the dispersion relation was large in the offshore area where the near inertial amplitude was large

surface current variability east of okinawa island obtained from remotely sensed and in situ observational data we investigated ocean surface current variability in the region east of okinawa island in the spring of 1998 using in situ and remotely sensed data including surface velocity estimates inferred from hf ocean radars most previous studies utilizing hf ocean radars were limited to shallow continental shelves in contrast most of the observation area in this study was in the open ocean during the observation period the hf ocean radars sampled a region where anticyclonic and cyclonic mesoscale eddies were adjacent to each other the hf radar derived ocean currents agree with those measured by a current meter the surface currents were highly variable in both time and space and were affected by the eddy field in the offshore region the current field was related to the near surface water temperature for example a local temperature rise was often associated with northeastward flows the surface currents in regions shallower than about 1000 m had a significant correlation with local wind forcing our hf ocean radars often detected a strongly convergent zone which was different in character from those described in previous studies in that it was in the deep ocean from other data such as national oceanic and atmospheric administration advanced very high resolution radiometer imagery we concluded that the convergent zone was due to mesoscale eddy fronts

ocean wave directional spectra and wave current interaction in the agulhas from the shuttle imaging radar b synthetic aperture radar sir b synthetic aperture radar ocean wave spectra for a 200 km pass crossing the agulhas current off the coast of africa are analyzed a significant enhancement of one spectral peak along the northern edge of the current is attributed both to amplification of the waves by refraction dominated wave current interaction and to transient specular backscatter contributions spatially correlated to the waves

synchronous changes in the seismicity rate and ocean bottom hydrostatic pressures along the nankai trough a possible slow slip event detected by the dense oceanfloor network system for earthquakes and tsunamis donet abstract we detected long term hydrostatic pressure changes at ocean bottom stations of the dense oceanfloor network system for earthquakes and tsunamis donet along the nankai trough off southwestern japan we detected these changes after removing the contributions of ocean mass variations and sensor drift from the records in addition we detected a decrease in the background seismicity rate of a nearby earthquake cluster that was synchronous with the hydrostatic pressure changes we interpreted these observed hydrostatic pressure changes to reflect vertical deformation of the ocean floor of 3 8 cm and we consider the cause of the seafloor crustal deformation to be a slow slip event sse beneath the stations because the pressure changes were observed at stations with distances less than 20 km to each other we inferred that the sse occurred in the shallow part of the sedimentary wedge such as on a splay fault system the synchronous observation of an sse and a seismicity rate change suggests that both were triggered by a change in the regional stress that may be associated with stress accumulation and release processes occurring along the nankai trough these data show that continuous and careful monitoring of crustal activities by donet stations provides an effective way to detect seismic and geodetic signals related to the occurrence of megathrust or other types of large earthquakes

wave current interaction near the gulf stream during the surface wave dynamics experiment this paper presents a case study on the wave current interaction near the local curvature of a gulf stream meander the wave data were obtained from in situ measurements by a pitch roll discus buoy during the surface wave dynamics experiment swade conducted off wallops island virginia from october 1990 to march 1991 owing to the advection of the gulf stream by the semidiurnal tide the discus buoy was alternately located outside and inside the gulf stream the directional wave measurements from the buoy show the changes in wave direction wave energy and directional spreading when waves encountered the current in the gulf stream meanders a wave refraction model using the ray tracing method with an estimated gulf stream velocity field and meandering condition was used to simulate wave refraction patterns and to estimate wave parameters at relative locations corresponding to buoy measurements the numerical simulation shows that a focusing zone of wave rays was formed near the boundary and behind the crest of a simulated gulf stream meander the focusing of wave rays causes changes in wave direction increases in wave energy and decreases in wave directional spreading which are in good agreement with the results from the buoy measurements

directional spreading of short wavelength fetch limited wind waves abstract observations of the spreading of short wavelength 5 m wind waves have been made with a steerable hf ocean surface radar in the nearshore zone in a stable offshore airflow the directional spreading lobe is significantly broader than that predicted from the model by hasselmann et al it appears that the spreading lobe is broader at high frequencies f 0 56 hz than at lower frequencies 0 2 f 0 5 hz for f fm ratios near unity in a fetch limited wind wave spectrum which has a peak at frequency fm

on the accuracy of hf radar surface current measurements intercomparisons with ship based sensors high frequency hf radar systems can provide periodic two dimensional vector current estimates over an area approaching 1000 km as the use of these hf systems has gained wider acceptance a number of attempts have been made to estimate the accuracy of such systems however comparisons of hf radar current estimates with in situ sensors are difficult to interpret since hf systems measure currents averaged over an area of 1 km 2 and to a depth of only 50 cm while in situ sensors measure currents at a point and somewhat greater depths 1 to 10 m previous studies of the accuracy of hf radar technology have thus attributed the differences observed between hf radar and in situ sensors to an unknown combination of vertical shear horizontal inhomogeneity in situ instrument errors and hf radar system errors this study examines the accuracy of hf radar current measurements using data from the 1993 high resolution remote sensing experiment conducted off cape hatteras north carolina data from four shipborne in situ current meters are compared with data from an ocean surface current radar oscr a commercial current measuring radar we attempt to discern the predominant sources of error in these data by using multiple simultaneous measurements from different sensors and by examining the variation of observed current differences as a function of location the results suggest an upper bound on the accuracy of the oscr derived radial currents of 7 to 8 cm s the measurement of near surface currents in the coastal environ ment is an important problem

analysis of roof fall hazards and risk assessment for zonguldak coal basin underground mines the roof fall hazards are frequent problems of underground coal mines which are generally unpredictable due to the associated uncertainties these uncertainties which arise from geological and stress conditions and mine environment make the control of roof fall hazards difficult in underground coal mines the most efficient method for coping with uncertainties in roof fall hazards is the use of risk assessment techniques in this study a risk assessment and management methodology is proposed for roof fall hazards in underground mines of the zonguldak coal basin the annual rates of roof falls obtained from the five mines in the basin are statistically analyzed the components of risk which are the probability of roof fall and consequences of roof fall hazard are identified and quantified the probability of roof fall is computed by fitting a distribution function to the annual roof fall while the consequences of roof falls are quantified based on a cost model then a decision analysis methodology for evaluating the performance of possible alternative action to be taken in order to decrease the risk is developed the results show that the underground coal mines in the zonguldak coal basin have considerably high risk levels and hence require comprehensive risk management schemes

field observations of radar backscatter from the ocean surface under low wind speed conditions unique simultaneous field observations of wind speed and images of vertically polarized radar backscatter from the ocean surface at low grazing angles during low wind and weakly stable stratification show interesting similarities and an important difference depending on whether the average wind is falling or rising when the wind speed begins to fall there is a delay before the area averaged radar backscatter begins to fall when the wind speed begins to rise the backscatter rises immediately this observation points to hysteresis in the relationship between radar backscatter and wind speed such that more wind is necessary to generate radar backscatter of a given intensity than is necessary to maintain it this likely arises from differences between the generation of wind driven gravity capillary waves and the maintenance of gravity capillary waves and or microbores also saturation was observed in the radar backscatter at wind speeds between 2 1 and 2 8 m s 1 for both rising and falling winds this saturation may be related to the energetics of the centimeter scale gravity capillary waves and or microbores that cause the backscatter during rising winds the backscatter may saturate because fine scale features of the ocean surface reach a maximum amplitude well before wind derived energy is transferred upscale to larger waves whose tilting effect would ultimately produce the familiar increase in radar backscatter with increasing wind during falling winds the backscatter may saturate because of residual momentum in the surface wave field finally for both rising and falling winds radar backscatter and wind speed are in general correlated above a wind speed of 1 7 m s 1 while below this value they are not this observation of the critical wind speed necessary to generate or maintain wind related backscatter is consistent with results from a recent field observation and with existing laboratory based observations

pore volume and surface area of the carboniferous coals from the zonguldak basin nw turkey and their variations with rank and maceral composition abstract the macropore volume micropore volume and surface area of carboniferous bituminous coals from the zonguldak basin in northwestern turkey have been determined furthermore variations of these coal properties with rank and maceral composition have been investigated helium density mercury porosimetry and low pressure co 2 gas adsorption measurements were performed in order to determine the pore volumes and the surface area of coals helium and mercury densities of the coals vary between 1 28 1 41 and 1 11 1 32 g cm 3 respectively the macropore volume determined by mercury porosimetry varies between 0 0065 and 0 0687 cm 3 g for the interpretation of the adsorption mechanism and for the determination of the respective pore volumes and surface areas langmuir and dubinin radushkevich d r equations were applied the micropore volume and respective micropore surface area values are ranging from 0 0139 to 0 0524 cm 3 g and from 42 to 160 m 2 g respectively the langmuir monolayer volume which can be considered as an estimate of the gas adsorption capacity varies between 14 and 37 cm 3 g the corresponding specific surface area values range from 80 to 216 m 2 g a comparison of pore volumes with rank and maceral composition of coals indicated that micropore volume decreases with increasing maturity up to a value of 1 0 r o and then increases with further increase of coal rank a similar trend is also observed with langmuir monolayer volume and specific surface area in general an indicative correlation could not be observed between maceral composition and pore volume and surface area however a weak correlation does exist between langmuir monolayer volume and vitrinite content

determination of underground mining induced displacements using gps observations in zonguldak kozlu hard coal basin abstract mining activities cause horizontal and vertical movements on the earth s surface as well as in underground which give rise to environmental economical judicial and urbanization problems these movements or displacements the results of collapsing vertical displacement swelling slope change bending and cracking are referred to as mining subsidence which depends on the depth and dimension of mined area production methods underground operating speed time and geological structure of area the mining subsidence eventually affects the development of cities and city life by causing damages and destruction on buildings and structures on the surface in order to study the displacements caused by on going mining activities city of zonguldak its town kozlu and its near surroundings are chosen since they constitute the center for hard coal basin in turkey for 160 years with a population of 300 000 and an area of 80 km2 this study details the results from a gps network conducted in the basin to determine the horizontal displacements on the surface created by the mining activities the displacement results obtained from this study have been found to range from 10 to 78 mm with 4 4 to 7 9 mm rmse values these results indicate that the surface of the basin is under these effects today

estimate of tidal constituents in nearshore waters using x band marine radar image sequences the accurate observation and prediction of tides are important in coastal waters a new method is proposed to estimate tidal constituents in nearshore waters from x band marine radar image sequences based on the modulation of wave height by tide the relative wave height is retrieved from the first principal component of the x band marine radar image sequence and a self adaption method is used to remove the low quality data under very low sea state to eliminate the influence of atmospheric planetary waves a type i chebyshev bandpass filter is applied to the time series of the derived wave heights relative tidal amplitudes and phases are then obtained through harmonic analysis of the filtered wave heights and true tidal amplitudes are derived through a linear relation while true tidal phases are obtained by cross spectral analysis the errors of the amplitudes of m2 s2 k1 and o1 tides retrieved from x band marine radar image sequences are 0 15 1 12 2 22 3 83 3 06 4 29 and 4 50 9 47 cm respectively as compared with those predicted by a numerical model the errors of m2 tidal phase are 3 27 4 59 it shows that the proposed method is appropriate for long and continuous observations of x band marine radar

wave current interaction study in the gulf of alaska for detection of eddies by synthetic aperture radar high resolution ers i synthetic aperture radar sar images are used to detect a mesoscale eddy such features limit dispersal of pollock larvae and therefore likely influence recruitment of fish in the gulf of alaska during high sea states and high winds the direct surface signature of the eddy was not clearly visible but the wave refraction in the eddy area was observed the rays of the wave field are traced out directly from the sar image the ray pattern gives information on the refraction pattern and on the relative variation of the wave energy along a ray through wave current interaction these observations are simulated by a ray tracing model which incorporates a surface current field associated with the eddy the numerical results of the model show that the waves are refracted and diverge in the eddy field with energy density decreasing the model data comparison for each ray shows the model predictions are in good agreement with the sar data

surface wave breaking over sheared currents observations from the mouth of the columbia river measurements of waves and currents from freely drifting buoys are used to evaluate wave breaking parameterizations at the mouth of the columbia river where breaking occurs in intermediate depths and in the presence of vertically sheared currents breaking waves are identified using images collected with cameras onboard the buoys and the breaking activity is well correlated with wave steepness vertical shear in the currents produces a frequency dependent effective current that modifies the linear dispersion relation accounting for these sheared currents in the wavenumber spectrum is essential in calculating the correct wave steepness without this wave steepness can be over under estimated on opposing following currents by up to 20 the observed bulk steepness values suggest a limiting value of 0 4 the observed fraction of breaking waves is in good agreement with several existing models each based on wave steepness further a semi spectral model designed for all depth regimes also compares favorably with measured breaking fractions in this model the majority of wave breaking is predicted to occur in the higher frequency bands i e short waves there is a residual dependance on directional spreading in which wave breaking decreases with increasing directional spread this article is protected by copyright all rights reserved

short wave ocean wave slope models for use in remote sensing data analysis recent developments in the directionality of sea waves are reviewed and adapted into a working model for radiometric remote sensing there is a weight of evidence both theoretical and observational that a bimodality exists in the directional wave spectrum for sea surface gravity waves at wavenumbers greater than the value at the peak of the spectrum we develop a model for the directional splitting which is consistent with observations but which extrapolates in a credible manner to the omnidirectionality observed at wavelengths around 0 3 m at shorter wavelengths the directional spectrum becomes unimodal and has an approximately constant shape across the gravity capillary wave regime a working model is suggested for the directionality of the wave spectrum to improve the analysis of radiometric sea surface data the model will also be useful for other analyses including active radar techniques which use bragg scatter

observations of surface wave current interaction abstractwave current interaction can result in significant inhomogeneities of the ocean surface wave field including modulation of the spectrum wave breaking rates and wave statistics this study presents novel airborne observations from two experiments 1 the high resolution air sea interaction hires experiment with measurements across an upwelling jet off the coast of northern california and 2 an experiment in the gulf of mexico with measurements of waves interacting with the loop current and associated eddies the significant wave height and slope varies by up to 30 because of these interactions at both sites whereas whitecap coverage varies by more than an order of magnitude whitecap coverage is well correlated with spectral moments negatively correlated with the directional spreading and positively correlated with the saturation surface wave statistics measured in the gulf of mexico including wave crest heights and lengths of crests per unit surface area show good agreement with seco

measurements of sea state variations across oceanic fronts using laser profilometry abstract as part of the grand banks experiment in may 1979 airborne laser profilometer measurements of the ocean wave field were made across a large cold water extrusion situated over the newfoundland ridge the feature is actually an extension of the labrador current which is bordered on the west side by the gulf stream and on the east side by the north atlantic current star shaped flight patterns were flown over the fronts on each side of the cold water feature a graphic technique was applied to the apparent wavenumber spectra in order to determine the changes in wave energy wavelength and direction of propagation of the dominant wind wave and swell components as they move across the fronts at the western front the sea state increased abruptly and the results indicate that wave current interactions were the most important mechanism for wave modification although boundary layer effects were present and increased wave breaking was observed at the eastern front changes in the swell are compared to

effects of mining subsidence on masonry buildings in zonguldak hard coal region in turkey gallerias are the underground constructed results of mining as these space in underground layers collapse horizontal and vertical ground movements occur and movement which may reach the earth s surface are known as mining subsidence the result of underground displacement may cause surface ground movement which can be detrimental to masonry buildings especially in hard coal regions thorough familiarity with general and regional characteristics of an affected area can assist reduction of the effects zonguldak and the nearby settlement area with a population of 300 000 constitute the centre of a hard coal basin where extensive mining has a history extending through 160 years mining constitutes the main economic activity in this region and consequently influences every aspect of life this study s intent is to identify the effects of mining subsidence on masonry buildings in the mining area of kozlu zonguldak turkey and illustrate them with selected images of damaged masonry buildings also included are satellite and mining galleria images

short wave directional properties in the vicinity of atmospheric and oceanic fronts 1 the author estimated and investigated mean wave directions and directional spread parameters of 0 505 hz ocean waves using data from 24 5 mhz hf ocean radar the author described temporal and spatial variabilities of the short wave field the short wave direction is a good indication of wind direction the spread parameter was related to the variability of wind direction the author examined the case that an atmospheric front or an oceanic front exists in the hf ocean radar observation area in the case of an atmospheric front the short wave direction changed with the passage of the atmospheric front furthermore the complicated frontal structure which cannot be verified from a weather chart was revealed narrow directional spread was observed in the vicinity of the convergent front which was reproduced using a simplified model based on the wave action conservation law the result shows that wave refraction associated with a frontal convergent zone is important in determining the spatial variability of short wave directional properties

study on electrical potential inversion imaging of abnormal stress in mining coal seam during the mining activities coal rock dynamic disasters have caused grievous casualties and massive property losses it is the severe problem for regional monitoring of abnormal stress electrical potential ep can be produced on coal rock under loading and its response is related closely with the loading stress and damage evolution meanwhile electric field inversion has the advantage to realize regionalization monitoring in the space to identify the abnormal stress localization characteristics in mining coal seam after theoretical derivation the strategy of ep inversion imaging on is studied under bilateral model further simulation experiment of coal rock under loading is conducted the abnormal probability zones of sample can be identified with ep inversion imaging while it corresponds with severe damage zones with significant crack propagation it can be utilized to reveal the localized characteristics of damage and failure of coal rock spatially finally the results of ep inversion in the mining coal seam indicate that the abnormal probability zones can be considered as stress concentration and dynamic hazard areas its effectiveness is verified by microseismic monitoring and rock burst hazard assessment the study provides a new idea to monitor abnormal stress zone regionally and forecast dynamic disasters in the field

effective resolution and drift of paroscientific pressure sensors derived from long term seafloor measurements 1 starting with the installation of the noaa tsunami early warning system dart in 1983 the paroscientific digiquarz broadband depth sensor has been deployed for long term ocean bottom pressure measurements in numerous marine investigations the sensor turned out to be very reliable with a good signal repeatability within a broad measuring range and high resolution however up to now its long term drift noise level and effective resolution under in situ conditions at the seafloor are only known from a few published studies and for a few sensors in this study we analyze 118 long term seafloor pressure time series longer than 2 months and up to a maximum time period of 9 years to investigate effective resolution and long term drift under in situ conditions the data are from dart ifm geomar lolem and cork stations the noise level of the data and therefore the mean sensor resolution are lower than an upper threshold of 20 7 pa corresponding to 2 07 mm equivalent water level for stations installed directly on the seafloor the noise level of cork sensors is much larger with a median value of 127 pa long term sensor drift is assumed to be composed of an initial exponential part and a subsequent linear drift in situ mean drift is 0 88 0 73 kpa a determined from all available data with a slight increase of drift with deployment depth for the first time we are able to quantify effective pressure resolution and drift of the widely used paroscientific pressure gauges under in situ conditions our results provide important constrains for the interpretation of seafloor pressure records however in situ self calibration procedures for the paroscientific sensors are still needed in order to benefit from high effective resolution and long term stability and also to increase accuracy especially for the monitoring of geodynamic processes at the seafloor

effect of current on the first order spectral power of high frequency radar wave current interaction is a common and important phenomenon in the ocean as an ocean remote sensing tool high frequency hf radar can be used to measure currents and wave parameters in this paper the possibility of studying wave current interaction using hf radar is investigated the first order spectral power fsp of hf radar is used to explore the effect of current on the bragg wave by analyzing the fsp change with current fsp current distribution we find that in deep water the wave current interactions mainly belong to 2 d refraction case while over a relatively shallow shelf the interactions are stronger and more complicated based on local topography and current field data at taiwan strait the simulation results obtained using the swan model confirm the 2 d refraction of the bragg wave when the wave current interaction is stable we compensate the fsp with radar measured currents according to the radar extracted fsp current distribution and achieve a more accurate wind estimation comparisons between the original and refined wind fields show the effectiveness and necessity of the current based compensation

radar derived interferometric surface currents and their relationship to subsurface current structure radar derived ocean surface currents are analyzed in conjunction with in situ acoustic doppler current profiler adcp measurements the interferometric measurements were collected by an x band imaging doppler radar in a manner analogous to those of along track interferometric synthetic aperture radar ati sar while the advent of ati sar has provided a new potentially powerful technique for current mapping the relationship between surface currents and interferometric velocity measurements is not yet clearly understood this paper presents comparisons between radar derived and in situ current measurements to develop a precise method for estimating the surface current from interferometric measurements the influence of long wave orbital velocities and the influence of bragg resonant waves are studied we find that coupling between the orbital velocity and backscattered power i e the modulation transfer function can bias surface current estimates potentially by up to 20 cm s 1 in an upwind viewing orientation furthermore experimental observations verify a cos 2n 0 2 analytical model for the directional spreading of bragg resonant waves extending our analysis to include subsurface currents case studies are presented under varying environmental conditions for which the vertical current structure changes considerably analysis of radar imagery yields both radial surface currents and vector subsurface current estimates derived from long wave dispersion characteristics combining these with coincident adcp measurements yields a vertical profile of current using these measurement techniques we make several observations within the upper meter of the ocean these profiles reveal the sensitivity of x band interferometric measurements to wind drift and the near surface current structure

episodic slow slip events in the japan subduction zone before the 2011 tohoku oki earthquake abstract we describe two transient slow slip events that occurred before the 2011 tohoku oki earthquake the first transient crustal deformation which occurred over a period of a week in november 2008 was recorded simultaneously using ocean bottom pressure gauges and an on shore volumetric strainmeter this deformation has been interpreted as being an m6 8 episodic slow slip event the second had a duration exceeding 1 month and was observed in february 2011 just before the 2011 tohoku oki earthquake the moment magnitude of this event reached 7 0 the two events preceded interplate earthquakes of magnitudes m6 1 december 2008 and m7 3 march 9 2011 respectively the latter is the largest foreshock of the 2011 tohoku oki earthquake our findings indicate that these slow slip events induced increases in shear stress which in turn triggered the interplate earthquakes the slow slip event source area on the fault is also located within the downdip portion of the huge coseismic slip area of the 2011 earthquake this demonstrates episodic slow slip and seismic behavior occurring on the same portions of the megathrust fault suggesting that the faults undergo slip in slow slip events can also rupture seismically

a numerical study of wave refraction in shallow tidal waters wave observations taken at two shallow water sites off the coast of south west wales u k are examined the buoys are located in a region of strong semi diurnal tides and the observations show significant variation at semi diurnal frequencies in period amplitude and direction the interaction between tides and waves is studied using linear theory of wave refraction by slowly varying currents and depths it is shown that quasi steady analytical models fail to reproduce the tidally induced variations in wave parameters a linear ray tracing model including the effects of both spatial and temporal variations in the tidal currents and elevations improves the simulation of the observed modification of the waves short period waves respond to variations in current refraction over a tidal cycle long period waves are more influenced by variations in water depth over a tidal cycle

study on the fracture characteristics of thick hard limestone roof and its controlling technique the taiyuan group is one of the coal bearing formations in shanxi province in which coal resource is extremely abundant no 15 coal seam is the main minable coal seam in taiyuan group and it develops with thick hard limestone roof which is a threat to safe and efficient mining because of the roof failure aiming at the geological setting of no 15 coal seam and its surrounding rock we conduct an experimental study on physical and mechanical properties of no 15 coal seam and its floor as well as roof and we also have an underground measurement on roof fracture width and floor loose range of headgate based on experimental results and fracture mechanics theory we established a thick hard limestone roof cracking model and discussed the factors that affect roof fracture initiation and extension the research results demonstrate that roof fracture height is affected by the horizontal stress surrounding rock deformation roof mechanical strength and roof span the deformation of wall and floor will induce the roof fracture extension the roof fracture extension is high in stress concentration area under the upper coal face residual coal pillar the fracture height can be effectively controlled by reducing surrounding rock loose range and improving mechanical strength of walls