Tuesday March 24th Posters

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Chair(s): Bradley Carr, WyCEHG - University of Wyoming

THE USE OF SYNTHETIC DATASET MODELLING TO ASSESS THE DETECTABILITY OF ERT SURVEYS WITH DIFFERENT ARRAYS WHEN IDENTIFYING KARST INTERVALS IN THE HES OF POITIERS (FRANCE) (Extended Abstract) Patrizio Torrese, Dipartimento di Scienze della Terra e dell’Ambiente, Università di Pavia Abstract Electrical Resistivity Tomography (ERT) surveys were undertaken at the Hydrogeological Experimental Site (HES) of Poitiers, France to identify karst intervals at depth of 35-40 m and 85-87 m host in the Dogger Limestone fractured-karst aquifer. Dogger Limestone occurs at a depth ranging between 30 and 120 m and is overlain by argillaceous limestone. Three-dimensional resistivity imaging was obtained from full inversion of combined 2D ERT data collected along five parallel 470 m long profiles with 50 m line spacing. Data were collected using both Wenner-Schlumberger (WS) and PoleDipole (PD) arrays. A 3d block measuring 481 X 203 m in size with a maximum depth of 100 m was surveyed. The hybrid array sequence (the combination of WS and PD array sequences) showed better imaging, due to the combination of the large vertical resolution of WS, large lateral resolution and penetration depth of PD. First, resistivity soundings have been sorted from ERT apparent resistivity data in order to verify the ERT detectability when identifying karst intervals. Then, synthetic dataset modeling was performed to assess the detectability of the ERT resistivity block when identifying karst intervals. Different starting models were implemented to perform forward modeling. The use of a very heterogeneous and anisotropic starting model implemented by using all information available from resistivity and stratigraphic logs and imagery of borehole walls provided unrealistic results. This is due to the too high level of detail of the stating model respect to the ERT system detectability and resolving ability. Then, a simpler, layered starting model comprising argillaceous limestone, low porosity limestone layers and karst intervals was implemented. Inversion of the synthetic dataset obtained by forward modeling was performed. Modeling allowed addressing different issues limiting the karst intervals detectability: an excessively low thickness with respect to the system’s ability; an excessively large resistivity gap when compared to the shallow argillaceous limestone that also reduced the investigation depth and led to a severe underestimate of the limestone resistivity; variation of the layers resistivity with depth. Keywords: ERT, array, karst, Poitiers, synthetic modeling

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3D POROSITY BLOCK OF A FRACTURED-KARST AQUIFER: COMPARISON BETWEEN THE POROSITY MODEL ACHIEVED BY 3D SEISMIC AND ERT IMAGING IN THE EXPERIMENTAL SITE OF POITIERS (FRANCE) (Extended Abstract) Patrizio Torrese, Dipartimento di Scienze della Terra e dell’Ambiente, Università di Pavia Fabio Colantonio, Università di Chieti-Pescara Pasquale Greco, Università di Chieti-Pescara Jean Luc Mari, Institut Français du Pétrole Energies Nouvelles (IFPEN) Gilles Porel, CNRS IC2MP UMR 7285 - Université de Poitiers Mario Luigi Rainone, Ce.R.S.-GEO Università “G. d'Annunzio" Chieti-Pescara – ITALIA Patrizio Signanini Abstract Three-dimensional porosity blocks of a Dogger Limestone fractured-karst aquifer were obtained at the Hydrogeological Experimental Site of Poitiers, France. Dogger Limestone occurs at a depth ranging between 30 and 120 m and is overlain by argillaceous limestone. Three karst intervals at depth of 35-50 m, 85 and 115 m have been revealed from vertical flowmeter data and high-resolution imagery of borehole walls. This paper compares the porosity blocks obtained from 3D seismic and resistivity imaging. Reflection seismic survey allowed generating a 3D seismic pseudo velocity block. The seismic interval velocities have been converted in resistivity. The empirical relationship between seismic velocity and true formation resistivity proposed by Faust (1953) has been used. Resistivity values were then converted into porosity values, by using the Archie’s law (1942). The 3D seismic pseudo porosity block allowed identifying three different water productive layers that are consistent with flowmeter and borehole imagery data: an upper layer at 35-40 m depth, an intermediate layer at 85-87 m depth and a lower layer at 110-115 m. Three-dimensional resistivity imaging was obtained from full inversion of combined 2D ERT data collected using both Wenner-Schlumberger (WS) and Pole-Dipole (PD) array sequences. The 3D resistivity blocks obtained from the WS, PD and the hybrid (combination of WS and PD) sequences were converted in porosity by using the Archie law (1942). The porosity model obtained by the hybrid array (and partly the PD array) seems to apparently identify the first two main karst intervals at 50 m and 85 m bgl. The comparison revealed that even if resistivity values are better correlated to porosity values than seismic velocity values, resistivity models were strongly affected by the occurrence of the shallow, low resistivity layer that reduced the investigation depth and by the system’s detectability ability with respect to the karst intervals thickness. Keywords: Porosity, reflection seismic, ERT, karst, Poitiers

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SURFACE-MINE NMR METHOD (Extended Abstract) Pan Jianwei, Institute of Geophysics and Geomatics, China University of GeosciencesWuhan Li Zhenyu*, Institute of Geophysics and Geomatics, China University of GeosciencesWuhan and China University of Geosciences-Wuhan, Wuhan City, PRC Peng Yao, Institute of Geophysics and Geomatics, China University of GeosciencesWuhan Abstract In exploring groundwater, surface nuclear magnetic resonance technology is more advanced than the traditional geophysical exploration methods. So, it has been widely used in many fields. But, the traditional SNMR method has many drawbacks too. For instance, it has long dead time, shallow detecting depth and poor lateral resolution. The development of this method is limited. The surface-mine NMR method is a new kind work pattern of NMR which can solve some problems that exist in the traditional method. The forward research shows that this kind of work pattern can define the threedimensional distribution of aquifer more accurately and this method points out another direction for the development of SNMR technology. Keywords: NMR, surface-mine pattern, forward

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USING BOREHOLE AND SURFACE GEOPHYSICS TO DEVELOP A CONCEPTUAL MODEL OF HYDROSTRATIGRAPHIC LAYERS, PECOS COUNTY REGION, TEXAS Jonathan Thomas, USGS Gregory Stanton, USGS Andrew Teeple, USGS Jason Payne, USGS Abstract Future groundwater availability is a concern in the Pecos County region of west Texas, where the Edwards-Trinity aquifer is an important water resource. The U.S. Geological Survey, in cooperation with the Middle Pecos Groundwater Conservation District, Pecos County, City of Fort Stockton, Brewster County, and Pecos County Water Control and Improvement District No. 1 developed a conceptual model of the Edwards-Trinity aquifer as part of a multi-phase study of the Pecos County region. Interpreting the hydrostratigraphic layer contacts from historic and newly collected borehole geophysical logs, surface geophysical soundings, and geologic data was a major part of model development. Approximately 200 borehole geophysical logs and 300 well reports, along with 4 time-domain electromagnetic soundings, and 13 audio-magnetotelluric soundings were correlated to determine tops and bases of the aquifer (hydrostratigraphic) layers; data collected by the USGS during 2009–11 and historical data from 1930–2011 collected by various State and local agencies were used in the model. Previous studies in this region indicate that groundwater flow is largely controlled by collapse structures and associated faulting. Multiple north-south and east-west geologic sections were constructed from hydrostratigraphic surface grids across the Pecos County region to analyze fault zones and local structural features. Updated grids were created to reflect the fault displacement associated with fault zones, in many cases showing units juxtaposed across the fault zone. The resulting hydrostratigraphic grids were used along with geochemistry and hydraulic-property data to develop the conceptual model, which aids in the understanding of the hydrogeologic framework, geochemistry, and groundwater flow. This information will be used to construct a groundwater flow model of the region. Keywords: Conceptual, Geophysics, Groundwater Resources

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BOREHOLE GEOPHYSICAL, FLUID, AND HYDRAULIC PROPERTIES WITHIN AND SURROUNDING THE FRESHWATER/SALINE-WATER TRANSITION ZONE, SAN ANTONIO SEGMENT OF THE EDWARDS AQUIFER, SOUTH-CENTRAL TEXAS Jonathan Thomas, USGS Gregory Stanton, USGS Abstract The freshwater zone of the San Antonio segment of the Edwards aquifer is used by residents of San Antonio and numerous other rapidly growing communities in southcentral Texas as their primary water supply source. This freshwater zone is bounded to the south and southeast by a saline-water zone with an intermediate zone transitioning from freshwater to saline water, the transition zone. During 2010 and 2011, the USGS, in cooperation with SAWS, conducted a study to further assess the potential for movement of the transition zone in part of the San Antonio segment of the Edwards aquifer. Data were collected within and surrounding the transition zone from 13 wells in four transects (East Uvalde, Tri-County, Fish Hatchery, and Kyle). Hydraulic head and geophysical log data were used to calculate equivalent freshwater heads and then analyzed to identify possible horizontal gradients across the transition zone and thus flow. Electromagnetic (EM) flowmeter logs were collected under both ambient and stressed (pumping) conditions and were processed to identify vertical flow zones within the borehole. The San Antonio segment of the Edwards aquifer (the study area) is about 175 miles long and extends from the western groundwater divide near Brackettville in Kinney County to the eastern groundwater divide near Kyle in Hays County. The four transects consist of two to five wells per transect and were configured approximately perpendicular to and across the expected trace of the freshwater/saline-water interface. Zones of high transmissivity throughout the study site were observed to not be continuous and are likely caused by localized secondary porosity such as intersecting faults or karst features. Keywords: Edwards, Geophysics, Karst

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ADAPTATIONS TO DIGITAL GEOPHYSICAL MAPPING (DGM) INSTRUMENT VERIFICATION STRIP (IVS) METRICS TO ACCOUNT FOR ROUGH TERRAIN: A CASE STUDY (Extended Abstract) Max W. Zelenevich, Battelle, Newtown, PA, USA Mark W. Blohm, Blohm Consulting, Evergreen, CO, USA F. Les Clarke, Battelle, Arvada, CO, USA Justin E. Peach, NAVFAC Northwest, Seattle, WA Abstract The Instrument Verification Strip (IVS) was developed to replace the expansive Geophysical Prove Out (GPO) in Munitions Response Sites (MRS) as a reliable and efficient way to verify the geophysical equipment used for Digital Geophysical Mapping (DGM) is working properly. Generally speaking, an average IVS consists of 5 Industry Standard Objects (ISOs) buried at various depths and orientations and sized to imitate potential munitions in the field. The advantage of ISOs is that they are consistent in design and construction; therefore the DGM response (amplitude) at various depths can be reliably computed and then compared to IVS surveys collected prior to and after DGM activities occur. The typical metrics to which the collected data are held to are generally positional +/- 9.8 in., and amplitude no greater than 20-25% the running average. As such, these metrics were also applied to the MRS in Adak, Alaska, a site characterized by rough terrain and steep slopes. In this project, three separate IVSs were utilized due to logistical reasons. These IVSs served six production DGM teams, one QC DGM team and one QA DGM team. Keywords: IVS, UXO, DGM, EM61, sensor

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GPR MEASUREMENTS CONDUCTED IN COURTYARDS OF NEW PALACE (TOPKAPI PALACE, TURKEY) Fethi Ahmet YukselL, Istanbul University Kerim Avci, Geometrik Mühendislik Jeofizik Mühendisi Nihan Hoskan, Istanbul University Hasan Fehmi Sahin Nevhiz Koyukan Abstract Topkapi Palace is the edge of the historical peninsula located between the Marmara Sea, the Bosphorus and the Golden Horn. The area called Seraglio was built in 1460-1478 by conqueror Sultan Mehmed. The region of the palace has an area of 700000 square meters and located on East Roman acropolis. The palace is a complex structure surrounded by 5 km length wall. It was used as the house of Ottoman sultans and management, education, art center of Ottoman Empire as well. Topkapi palace is a classic palace like other Turkish palaces known in history. The area of the palace is composed of courtyards with different functions. Courtyards are devided by monumental gates and other functional structures are interspersed around the courtyards. The Palace was continuosly developed from the begining by additions and changes made by Ottoman sultans. The sultans moved to Dolmabahce Palace in 1853. Topkapi Palace was no longer official palace after that point. The palace met with former simple beauty by permanent repairs during 50 years in period of Republic of Turkey. It is the oldest and most extensive one in the world and have been used as a museum since 1924. GPR measurements were conducted by using 250 MHz shielded antenna in Regimental square (1.courtyard), Court square (2.Courtyard), Enderun courtyard (3.courtyard) and Tulip garden (4.courtyard) of Topkapi palace. GPR measurements were performed as 1m interval of width and length on profiles. Two and three- dimensional images were obtained from GPR data. Once generated level maps and three dimensional cube models are examined, high amplitude anomalies that show geometric forms like walls, columns, cisterns belonged to the East Roman period were displayed. Keywords: GPR, Topkapi Palace, Acropolis, Istanbul

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ARCHAEOGEOPHYSICS STUDIES IN OLD VAN (TUSHPA), WHICH IS CAPITAL CITY OF KINGDOM OF URARTU Nihan Hoskan, Istanbul University Fethi Ahmet Yuksel, Istanbul University Kerim Avci, Geometrik Mühendislik Jeofizik Mühendisi Erkan Konyar, Istanbul University Can Avci, Istanbul University Abstract The old Van city is located in the east of Turkey and also located at the south of Van Lake and at the south of Van Castle built on Van cliff. The city known as Tushpa lower site is surrounded by walls that fortified with donjons. The castle walls were made as two levels and there is a ditch in the front of outer wall. There were three gates on the east, south and west side of the walls that are largely destroyed today. The city was abondened due to great destruction and fires at the time of Russian invasion in 1915. Some mosques like Kaya Celebi, Sheikh Abdurrahman Baba and mausoleum were restored but they were heavily damaged during the 2011 Van earthquake. The archaeogeophysics studies were conducted in the east of Kaya Celebi mosque and in the north and northeast of Grand mosque. GPR and magnetic measurements were made along 1 meter intermitently profiles. Archaeological remains of old periods were determined beneath the study area with two and three-dimensional images obtained from GPR data. The stone paved path was determined from the images of GPR measurements conducted in the east of Kaya Celebi mosque. The conducted excavation shows that EastWest directed road has two levels and it was built at the different times. In addition this, structures and channels are determined in the edges of the road. GPR and magnetic instruments were used in geophysical measurements conducted in the plots located around Grand Mosque. High-amplitude anomalies of archaeological materials and architectural structures were observed in the images prepared from GPR data. Once total magnetic and vertical magnetic gradyan maps created with the evaluation of magnetic measurements are observed, anomaly distrubitions belonging to archaeological remains were displayed in the different levels of the portions of the different old periods. Keywords: Van, Urartu, Tushpa, GPR, Magnetic, Archaeogeophysics

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GEOPHYSICAL RESEARCH IN THE CASTLE OF SAVSAT, ARTVIN (TURKEY) USING GEORADAR AND MAGNETIC METHODS Kerim Avci, Geometrik Mühendislik Jeofizik Mühendisi Fethi Ahmet Yuksel, Istanbul University Kubra Erguven Nihan Hoskan, Istanbul University Osman Aytekin, Yuzuncu Yil University Abstract Savsat Castle is located on the Northeast of Turkey. The castle is about 67 km away from the city center and 3 km away from the town center. The castle has 12 meters elevation difference in its own area and has 941 meters avarage altitude. Despite the standing walls reached the height of 10 meters, it is understood that they are orginally higher than this. At the direction of the entrance, a very small part of the protected wall was monitored. The piles of stones fallen from the walls have already covered a substantial part of castle interior. In Savsat castle, Artvin, geophysical surveys were performed in order to determine if there are any architectural ruins beneath the piles of stones covering interior space of the castle. Once the magnetic maps are examined. The regular anomalies may belong to basic building foundations. The irregular anomalies may belong to the piles of stones or walls foundations and the column of the building. A trial trench was made at the location in which the anomalies were detected and structural elements were observed. GPR measurements were conducted by using 250 MHz shielded antenna in the front of east wall in which magnetic measurements were performed. GPR measurements were carried out at the opened floor and at the locations that have not been excavated yet. Georadar measurements were made in the total of 113 profiles and 18 regions of castle interior. After data proccessing steps of obtained GPR radargram, two and three dimensional underground georadar images were obtained. Once generated level maps and threedimensional cube models are examined, high amplitude scattered anomalies and geometric forms that may be structural elements were displayed beneath the excavated trenches. In the areas that have not been excavated yet, distrubutions of regular and irregular anomalies were displayed. Keywords: GPR, Magnetic, Savsat Castle, Artvin

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TESTING GEOPHYSICAL METHODS TO EXPLORE ROCK SOURCES FOR ROAD CONSTRUCTION AGGREGATES AT TIMBER SALE SITES IN WESTERN WASHINGTON, PACIFIC NORTHWEST OF THE UNITED STATES Recep Cakir, Washington State Department of Natural Resources Koichi Hayashi Terran Gufler, Washington State Department of Natural Resources John E. Jenkins, Washington State Department of Natural Resources Venice Goetz, Washington State Department of Natural Resources Joseph Schilter, Washington State Department of Natural Resources Timothy Walsh, Washington State Department of Natural Resources Abstract The Washington State Department of Natural Resources (WADNR) manages three million acres of lands in Washington State to provide revenue from timber sales and other forest products for trust beneficiaries such as public schools, universities, and other institutions. Rock sources are needed to supply aggregate for road construction in the timber harvest areas and that can be challenging to locate them in rugged terrain conditions of heavily forested areas. If the desired quality rock is not found close to a timber harvest area, then the timber sale project may not be profitable and thus represent a revenue loss to the trust beneficiaries. To explore the desired rock sources in the areas we tested various geophysical methods that are reliable, relatively inexpensive, unobtrusive, and portable for use in remote locations. Our objectives are to identify and use a feasible and practical geophysical method or combination of methods to 1) locate bedrock sources, and 2) expand existing quarries for road construction. In addition, it is desired to a) identify the extent and thickness of overburden soils, b) characterize the rock quality beneath the overburden, and c) identify if groundwater is present and a significant concern. Our approach includes geologic reconnaissance in combination with one or more of the following geophysical methods: active/passive shallow seismic, single-station passive seismic, electric resistivity (OHM-Mapper), Ground Penetration Radar (GPR), and Electromagnetic Induction (EMI). We tested these methods at three sites in western Washington. Our test study results evaluate the feasibility of each geophysical method used to meet the objectives for rock exploration. From our study results we recommend P-wave seismic refraction and GPR surveys for the rapid exploration of the desired source rock, and electromagnetic induction and/or electric resistivity survey methods (supplementary to seismic and GPR surveys) to explore the ground water and/or subsurface fracture conditions. Keywords: Forest Road Construction, Seismic Velocity, GPR, Electric Resistivity, Electromagnetic

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THE GEOARCHEOLOGICAL AND GEOPHYSICAL(GPR) RESEARCH FOR KADIKALESI (ANAIA) ANTIC CITY IN AYDIN, KUSADASI Mahmut Ziya Gorucu, Istanbul University Fethi Ahmet Yuksel, Istanbul University Kerim Avci, Geometrik Mühendislik Jeofizik Mühendisi Nihan Hoskan, Istanbul University Emine Avci, Geometrik Engineering Consultancy Subsurface Research Zeynep Mercangoz, Ege University Abstract Kadikalesi (Anaia) Tumulus(hill town) takes place in Davutlar village which is 8 km northern and belongs to Kuşadası in Aydın city. The antic city was placed on a point that controles Samos(Sisam) island which was very important to manage Eagean Sea’s. For a long time Between prehistorical term and Ottoman Empire Kuşadası (Anaia) hill town had been a settlement and it was built for protection the port of Byzantion Anaia Geophysical Works on Anaia Castle and around we used GPR and magnetometer for research. During this work in the castle different locations we did use georadar methods nad some magnetic methods. We got some 2D and 3D profile by using Data from GPR and magneometer measurements After this works it was found the axis of the church and the base of the castle and church. The base of Kuşadası (Anaia) Antic city Kuşadası there are some Formations by covering Menderes Massive Formation. These formations are Şenköy formation Early-middle Permian age and it is transitive to each other. After these formation Bafa formation which is Upper Permian-Eraly Triasic age overlies it. Then Bozdağ formation which is middle Triasic-Upper Cretesaous aged comes by covering the Bafa. After this Zeytinköy formation overlies with tectonic contact as a disconformity represented by flysch. In the region Terrestrial sediments which is Tertiary aged covers all aother formations by disconformity These last unit is represented by two formations such as Söke formation which is Miocene aged and terrestrial sediments and Balatcik and Hisartepe volcanic rocks. Quaternary sediments are terrestrial rocks. In this work we got some samples from the Antic city and from field to compare petrographic and petrological in the microscope. As a result the material fort he antic city supplied mostly from near area. But some of them come from far northern or far eastnorthern of the region. Keywords: Anaia, GPR, Magnetic, Geology, Archeogeophysical, Geoarcheology, Permian, Kuşadası, Turkey

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DO AIR-FILLED CAVES CAUSE HIGH RESISTIVITY ANOMALIES?! A SIXCASE STUDY FROM THE EDWARDS AQUIFER RECHARGE ZONE IN SAN ANTONIO, TEXAS Mustafa Saribudak, Environmental Geophysics Associates Abstract Of course they do! But it is rarely that caves are purely filled with air. A variety of sediments accumulates in caves and can be preserved more or less intact for long periods of time (Palmer, 2007). Presence of sand and gravel and clay deposits, mineralization, faults and fractures, perched water in caves are the rules rather than the exception. The existence of caves represents a hazard for urban areas. Therefore it is important to know the size, position and depth of caves before building or reconstruction. Cavity imaging using geophysical surveys has become common in the San Antonio area since early 2000 although their use has been going on in other parts of country for the last 25 years. It appears from these studies that the resistivity imaging method has been the primary technique among others, such as gravity, ground penetrating radar, magnetic, conductivity, etc. Resistivity values, in theory, increase dramatically over air-filled cavities. So it is expected to find high resistivity anomalies over the air-filled cavities. This article describes only resistivity imaging data collected over six caves between the years of 2000 and 2005, which are air filled and are located in the northern part of Bexar County, San Antonio, Texas. All caves but one was encountered through drilling and/or excavation for building and utility lines or power pole reconstructions. The study area falls into the part of the Recharge Zone of the Edwards Aquifer region and it represents a well- developed karstified and faulted limestone. The purpose of the study is to show that air-filled cavities do not always cause high resistivity anomalies due to the complex subsurface conditions, and they are sometimes are not separable as a cave anomaly from the surrounding rocks. Keywords: Resistivity, caves, air-filled, Edwards Aquifer, San Antonio

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JOINT HYPOCENTER-VELOCITY INVERSION OF SURFACE WAVE ARRIVAL TIMES TO LOCATE HYPOCENTER OF UNEXPLODED ORDNANCE MUNITION (UXO) Issam Bakari, Institut National de la recherche scientifique (INRS-ETE), Canada, Québec Bernard Giroux, Institut National de la recherche scientifique (INRS-ETE), Canada, Quebec Sonia Thiboutot, Defence Research and Development Canada, Canada, Quebec Abstract Unexploded ordnances (UXO) in training ranges cause a significant risk to the environment and human activity after the abandonment of training fields. It was recently proposed (VanDeMark et al., 2012; VanDeMark et al., 2013) to detect and locate the occurrence of OXUs during firing exercise through microseismic monitoring, to allow their rapid removal. In this contribution, the location problem is addressed. The proposed method is based on the inversion of surface wave arrival times recorded by seismic sensors buried around the range. The method consists in minimizing, by the least-squares method, the difference between observed and predicted arrival times of the surface wave generated from UXO impacts. Due to the non-linearity of the problem, the velocity model and the initial hypocenters are iteratively updated until the residuals between predicted and observed arrival times fall within a prescribed limit. The location algorithm is based on the approach of Block (1994) and Giroux (2001) but with surface waves traveltimes computed on triangular meshes instead P and S waves on rectangular grids. The algorithm was tested with synthetic data which consist of the arrival times of surfaces waves generated by the ray tracing code under heterogeneous velocity. Each source of arrival time has thus a known coordinate hypocentre and origin time. The velocity model was estimated by 20 calibrations shots whose origin time and locations at the free surface are known. Tests were conducted but applying varying quantities of noise on the synthetic arrival times in each seismic sensor. The results obtained show that the previous approach is feasible; it is possible to locate the UXO's hypocenters with good accuracy (error of the hypocenter location reached 1-2 meter) under low noise condition (3%). However, under strong noise (15%) the accuracy of localisation decreases significantly (error of the hypocenter location reached 40 m). This notwithstanding, error of location depends on the ray-station coverage within the grid and the initial velocity model depend upon the number of calibration shot. Keywords: Microseismic, Surface waves, inversion, monitoring, UXO, Hypocenter

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TEMPERATURE AND RESISTIVITY INVESTIGATIONS TO DETERMINE ZONES OF STREAMBED LEAKAGE AND ABATE ABANDONED MINE DRAINAGE IN THE UPPER SCHUYLKILL RIVER, SCHUYLKILL COUNTY Laura Sherrod, Kutztown University Charles Cravotta, U.S. Geological Survey Alex Spielman Abstract Pennsylvania has an estimated 750 km2 of abandoned mines and more than 8,000 km of streams degraded by abandoned mine drainage (AMD). Stretching 210 km from its headwaters in Schuylkill County to its mouth in Philadelphia, the Schuylkill River originates partly as AMD from extensive underground anthracite mines. The AMD forms as recharge leaks through streambeds, mine spoil, and mine workings where it dissolves pyrite oxidation products and acquires sulfate, iron, and other contaminants. Abatement of streamflow losses from tributaries such as West Creek to underground mines in the headwaters is key to improving downstream water quality. Because West Creek loses perennial flow to underlying mines, its downstream flow is intermittent while associated AMD is sustained. Leakage of stream water from the channel combined with high evapotranspiration in the summer result in a dry creek bed. Along some losing reaches, inflows of groundwater can add to the total flow lost from the stream and influence downstream water chemistry. To restore the aquatic habitat within West Creek and decrease the volume of AMD, zones of streamflow leakage may be identified and sealed. Resistivity surveys were performed and temperature flux measurements taken to pinpoint zones of groundwater-surface water interaction. An MPT DAS-1 was used for the resistivity surveys, traversing twelve 155 m sections of West Creek, using a dipole-dipole array with 32 electrodes and a spacing of 5m. Data was processed with the resistivity inversion software ERTLab. Vertical temperature probes consisting of four iButtons spaced at 2 to 3 cm intervals were imbedded in sections of anomalous resistivity to determine the direction of groundwater flux using the MatLab program VFLUX. These results, along with stream discharge and water chemistry measurements, pinpoint seepage loss zones where stream restoration may prevent water from exiting the stream channel to become AMD from underlying mines. Keywords: Resistivity, Temperature, AMD, Streamflow

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APPLICATION OF ELECTRICAL RESISTIVITY TOMOGRAPHY IN TWO WETLAND SYSTEMS NORTH OF THE TANANA RIVER, INTERIOR ALASKA Chrstopher Conaway, USGS Tom Lorsenson Cordell Johnson, USGS Mark Waldrop, USGS David McGuire, University of Alaska Fairbanks Merritt Turetsky Eugénie Euskirchen, University of Alaska Fairbanks Peter Swarzenski, USGS Abstract Electrical resistivity tomography (ERT) was used to investigate distribution and changes in permafrost, active layer thickness, and other features at two peatland sites on the narrow alluvial plain north of the Tanana River 20 km southwest of Fairbanks, Alaska, in June and September 2014. Both sites are in or near the Bonanza Creek Experimental Forest. Surface-based 2D measurements were conducted using a multichannel receiver and a cable with 56 electrodes at 2 meter spacing. Several conventional array types were compared at both sites: dipole-dipole, Wenner, and Schlumberger. A 180 meter transect was run from a mixed birch-spruce area through transitions into a moderate fen area (“fen site”), and a 200 meter transect was run from a black spruce forest through transitions into a bog area (“bog site”). The fen site transect results suggest a subsurface of predominantly ice-rich permafrost in the tree-populated area through a tussock area grading into a seasonally frozen layer overlying deeply thawed subsurface in the fen area. A combined Schlumberger-Wenner array appears better in resolving other horizontally-distributed features interpreted as floodplain deposits of silt, sand, and gravel. The bog site transect results show a seasonal frozen layer extending from near the surface to a depth of about 3 meters that is overlying deeper ice-rich material beginning at about 12 meters depth in the black spruce area grading into shallower permafrost in the sphagnum-dominated bog area. The bog area itself can be separated into bog having high-resistivity (ice-rich) zone beginning at a depth of 2 meters or less, and a collapse scar feature shown as a low-resistivity (unfrozen) zone extending to about 6 meters in depth. The edge of the collapse scar bog feature appears best resolved with the dipoledipole array type. Overall, the results highlight the utility of ERT to characterize permafrost and thaw features both here and elsewhere. Keywords: electrical resistivity tomography , wetland, active layer, permafrost, Alaska

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SPECTRUM ANALYSIS OF RANDOM SAMPLING OF MARINE TOWED STREAMER

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Peng Li Abstract At present, sampling of marine towed streamer seismic acquisition is appropriate only when receiver points are in the in-line direction. However, sampling is inadequate when the shot points in the in-line, cross-line direction and receiver points in the cross-line directions. To analyze the anti-aliasing characteristic, we studied random sampling of a marine towed streamer with harmonic seismic signals and synthetic records. In conditions of regular space sampling, we respectively analyzed the spectrum characteristics of adequate sampling and inadequate sampling, and the reason of spatial aliasing. Based on regular sampling analysis, we performed random sampling, and spectrum analysis for harmonic seismic signals and synthetic records, and studied the effect of random sampling on alleviating aliasing. The results show that (1) if a shot interval of a marine towed streamer is greater than the Nyquist sampling interval, data spectrum exists different degree of aliasing. In order to improve the data resolution, it is needed to reduce the shot interval to increase the spatial sampling rate; and (2) if a shot interval of a marine towed streamer cannot satisfy the Nyquist sampling theorem in the case of random distribution of a towed streamer, random distribution of shot points with random sampling can reduce the aliasing effect of seismic data. Keywords: marine towed streamers; random sampling; Fourier transform

SAGEEP 2015 630