Most commonly ground-penetrating radar is used but this may not always be an optimal search detection technique. Near-surface Geophysics Geophysical survey techniques provide data at a variety of scales, from the regional geologic setting to the site-specific level, and can be applied to a range of … The Near-Surface Geophysics Early Career Achievement Award is given annually and recognizes significant contributions to the field of near-surface geophysics by an early career researcher. There are various electrode configurations of equipment, the most typical using two current and two potential electrodes in a dipole-dipole array. These may include surveys of gravity, magnetism, seismicity, or magnetotellurics. The infill may also be detectable using ground-penetrating radar. [1], The reciprocal of conductivity, electrical resistivity surveys measure the resistance of material (usually soil) between electrical probes, with typical penetration depths one to two times the electrode separations. For more information on the Special Issue click here. Geophysics at the ISGS is a Near-surface Geophysics research program, focusing on methods and tools tailored to characterization of the upper 300 feet below land surface. You can read part one here, and part … [7], Seismic refraction can be used not only to identify layers in rocks by the trajectories of the seismic waves, but also to infer the wave speeds in each layer, thereby providing some information on the material in each layer. Near Surface Geophysics has published a Special Issue on Geoelectrical Monitoring. The Near Surface Geophysics (NSG) group at Rutgers- Newark focuses on advancing the application of near surface geophysical techniques to improve understanding of subsurface … Often a set of measurements are along a line, or traverse. [19] Techniques vary depending upon the target and host materials as mentioned. In addition to the practical applications, near-surface geophysics includes the study of biogeochemical cycles. You can read the published Special Issue here. We encourage submissions that combine multiple approaches, including multi-disciplinary modeling or machine learning to effectively assess natural hazards. and you may need to create a new Wiley Online Library account. A region of higher electrical conductivity may have water or galena. We have welcomed papers that described new approaches to instrumentation and measurement, monitoring design considerations, time-lapse inversion and modelling, and novel applications of geoelectrics for engineering and environmental monitoring. Box 2229 Redmond, … [3][4], In studies of the solid Earth, the mean feature that distinguishes geophysics from geology is that it involves remote sensing. Geotomographie provides complete solutions for borehole and near-surface seismic surveys to geophysical, engineering and mining ... John Liu Global Geophysics P.O. It is also used to look for human artifacts. Near-Surface Geophysics presents concepts and fundamental of near-surface geophysics in Part 1 and applications and case histories in Part 2. Near Surface Geophysics is an international journal for the publication of research and development in geophysics applied to near surface. Geophysics of first tens of meters below surface, "GPR and bulk ground resistivity surveys in graveyards: Locating unmarked burials in contrasting soil types", "Geophysical surveys to help map buried igneous intrusions, Snowdonia, North Wales, UK", "Long-term time-lapse microgravity and geotechnical monitoring of relict salt mines, Marston, Cheshire, U. K.", "The use of geoscience methods for terrestrial forensic searches", "GPR investigations to characterize Medieval and Roman foundations under existing shop premises: a case study from Chester, Cheshire, UK", Quarterly Journal of Engineering Geology & Hydrogeology, "Near-surface geophysics: A new focus group", Eos, Transactions, American Geophysical Union, "Submergence of Ancient Greek Cities Off Egypt's Nile Delta—A Cautionary Tale", 10.1130/1052-5173(2004)014<4:SOAGCO>2.0.CO;2, Near Surface Geophysics Focus Group (AGU), The Near-Surface Geophysics Section of the Society of Exploration Geophysicists (SEG), Near Surface Geophysics: A Resource for all Things Geophysical, Near Surface Geophysics Specialist Sub-Group of the Geological Society of London, https://en.wikipedia.org/w/index.php?title=Near-surface_geophysics&oldid=997547933, Creative Commons Attribution-ShareAlike License, This page was last edited on 1 January 2021, at 02:06. Enter your email address below and we will send you your username, If the address matches an existing account you will receive an email with instructions to retrieve your username, © European Association of Geoscientists & Engineers, By continuing to browse this site, you agree to its use of cookies as described in our. [13], Geophysical methods were extensively used in recent work on the submerged remains of ancient Alexandria as well as three nearby submerged cities (Herakleion, Canopus and Menouthis). Many of our methods and tools target much shallower depths, and applications in forensics and archeology are focused on characterizing materials and objects within the upper 3-10 feet below land surface. Various physical phenomena are used to probe below the surface where scientists cannot directly access the rock. Search for more papers by this author. Or a set of parallel transects may be interpreted using a 2½D model, which assumes that relevant features are elongated. The study published in Near Surface Geophysics details what they found: fully buried structures, underground ammunition magazines and tunnels that matched the … For more complex features, a 3D model may be obtained using tomography. Near Surface Geophysics is an international journal for the publication of research and development in geophysics applied to near surface. Box 2229 Redmond, … Near Surface Geophysics is an international journal for the publication of research and development in geophysics applied to near surface. Questions (40) Publications (45,622) Questions related to Near Surface Geophysics. Apart from standard geophysical services, GT offers a variety of near-surface geophysical in the field of geology, hydrogeology and environmental … Given a model of the density, the gravity measurements at the surface can be predicted; but in an inverse problem the gravity measurements are known and the density must be inferred. Near-surface geophysics is the use of geophysical methods to investigate small-scale features in the shallow (tens of meters) subsurface. For a good interpretation the geophysics model must be combined with geological knowledge of the area. R.R. [9], High precision gravity measurements can be used to detect near surface density anomalies, such as those associated with sinkholes and old mine workings,[10] with repeat monitoring allowing near-surface changes over these to be quantified. P-waves travel faster than S-waves, and both have trajectories that bend as the wave speeds change with depth. [15] In addition, they helped to locate structures that may be the lost Great Lighthouse and palace of Cleopatra, although these claims are contested.[14]. Unlike many traditional exploration geophysics textbooks, this one also includes the basic geophysical exploration data analysis and inversion chapters. Foundations and walls may also have a magnetic or electrical signature. They do experience significant changes with soil moisture content, a difficulty in most site investigations with heterogeneous ground and differing vegetation distributions.[1]. A geophysical survey is a set of measurements made with a geophysical instrument. There are airborne, land- and water-based systems currently available. Areas of near-surface geophysics investigation include engineering, … Many of these methods were developed for oil and mineral exploration but are now used for a great variety of applications, including archaeology, environmental science, They can also be used to date artifacts. Near-Surface Geophysics presents concepts and fundamental of near-surface geophysics in Part 1 and applications and case histories in Part 2. [5] Technologies used for geophysical surveys include: The raw data from a geophysical survey must often be converted to a more useful form. The signal-to-noise ratio may be improved by repeated measurements of the same quantity followed by some sort of averaging such as stacking or signal processing.[5]. Our geophysicists and geologists have experience for choosing the appropriate methods for client projects. In one … My interests lie at the intersection of optimizing geophysical techniques, multidiscipline research, and 3D visualization. Near-Surface Geophysics: A New Focus Group The formation of the NS focus group was driven by the vast opportunities to improve PAGE 249 short- and long-term goals for the focus group, … The conclusion and the results of our 3 part series on the application of near-surface geophysics. Please check your email for instructions on resetting your password. Near-surface geophysics is part of WikiProject Geology, an attempt at creating a standardized, informative, comprehensive and easy-to-use geology resource. Civil investigations are more often trying to determine the location, amount and (more tricky) the timing of illegally dumped waste, which include physical (e.g. "In summary, this is an excellent advanced near-surface applied-geophysics textbook. Once a good profile is obtained of the physical property that is directly measured, it must be converted to a model of the property that is being investigated. Near Surface Geophysics jobs. If you do not receive an email within 10 minutes, your email address may not be registered, 13 jobs to view and apply for now with AGU Pathfinder Career Centre [1] In rural areas conventional SI methods may be employed but in urban areas or in difficult sites, targeted geophysical techniques can rapidly characterise a site for follow-up, intensive surface or near-surface investigative methods. Click here for more information on the Special Issue. Explore the latest questions and answers in Near Surface Geophysics, and find Near Surface Geophysics experts. which involves boreholes and trial pits. They are used for geotechnical, archaeology and forensic geophysics investigations and have better resolution than most conductivity surveys. It is closely related to applied geophysics or exploration geophysics. The method is much like echo sounding. [1] It is closely related to applied geophysics or exploration geophysics. The award is presented at the Near-Surface Geophysics … Department of Geology and Geophysics, Texas A&M University, College Station, TX, 77843 USA. Geotechnical investigations use near-surface geophysics as a standard tool, both for initial site characterisation and to gauge where to subsequently undertake intrusive site investigation (S.I.) Near Surface Geophysics is an international journal for the publication of research and development in geophysics applied to near surface. Near Surface Geophysics is an international journal for the publication of research and development in geophysics applied to near surface. [5], The reduced data may not provide a good enough image because of background noise. Published on behalf of the European Association of Geoscientists & Engineers. I specialize in shallow geophysics… For example, gravity measurements are used to obtain a model of the density profile under the surface. Near-Surface Geophysics focuses on the development and application of any and all geophysical methods to study the near-surface region of the Earth, to advance the fundamental science of geophysical … Near-Surface Geophysics Services. Depending on the data coverage, the model may only be a 2D model of a profile. [7], Magnetic surveying can be done on a planetary scale (for example, the survey of Mars by the Mars Global Surveyor) or on a scale of meters. Many of these methods were developed for oil and mineral exploration but are now used for a great variety of applications, including archaeology, environmental science, forensic science,[2] military intelligence, geotechnical investigation, treasure hunting, and hydrogeology. Engineering geophysics comprises of spatial studies of the Earth’s surface and subsurface to detect local anomalies in the subsurface that create constructional instabilities/failures and to … It can be used to identify folding and faulting, and to search for oil and gas fields. Geophysical methods can be used to find or map an archaeological site remotely, avoiding unnecessary digging. of Geology and Geophysics cost center that consists of near-surface, exploration, hydrogeophysical and geotechnical surface geophysical equipment (surface… The near-surface geophysics community includes scientists and professionals from academia, industry, and government. This problem has uncertainties due to the noise and limited coverage of the surface, but even with perfect coverage many possible models of the interior could fit the data. [1], Bulk ground conductivity typically uses transmitter/receiver pairs to obtain primary/secondary EM signals from the surrounding environment (note potential difficulty in urban areas with above-ground EM sources of interference), with collection areas depending upon the antennae spacing and equipment used. [14] Methods that included side-scan sonar, magnetic surveys and seismic profiles uncovered a story of bad site location and a failure to protect buildings against geohazards. Forensic geophysics is increasingly being used to detect near-surface objects/materials related to either a criminal or civil investigation. [5], Seismology makes use of the ability of vibrations to travel through rock as seismic waves. Bringing the subsurface into view. Field of Specialization: Near-Surface Geophysics My research in near surface geophysics focuses on using the geophysical method, nuclear magnetic resonance (NMR), to understand … Near Surface Geophysics Instrumentation Center (UWNSG): The UWNSG is a UW Dept. [7], Seismic reflection is used for imaging of nearly horizontal layers in the Earth. In surveys of a potential archaeological site, features cut into the ground (such as ditches, pits and postholes) may be detected, even after filled in, by electrical resistivity and magnetic methods. We invite papers that describe new developments in hazard characterization and monitoring using the broad range of geophysical sensing, and integration with geological, geotechnical, hydrological and environmental data. On a regional scale, profiles can be combined to get sequence stratigraphy, making it possible to date sedimentary layers and identify eustatic sea level rise. Applied geophysics projects typically have the following elements: data acquisition, data reduction, data processing, modeling, and geological interpretation.[5]. Dedicated to Stanley H. Ward, Near-Surface Geophysics … Innovation in Near-Surface Geophysics: Instrumentation, Application, and Data Processing Methods offers an advanced look at state-of-the-art and innovative technologies for near surface geophysics… The Special Issue highlights the recent advances in the application of quantitative geophysical methods (both seismic and non-seismic) to marine shallow subsurface problems. Welcome to the Near Surface Geoscience Conference & Exhibition Welcome by Alireza Malehmir, NSG Division Chair On behalf of the EAGE Near Surface Geoscience Division, I cordially invite … The application of Near-Surface Geophysics: Conclusion. Magnetometers are used to search for anomalies produced by targets with a lot of magnetically hard material such as ferrites. These waves come in two types: pressure waves (P-waves) and shear waves (S-waves). Working off-campus? JEEG is published quarterly and is a leading peer-reviewed scientific journal devoted specifically to the near surface geophysics community (Impact Factor: 1.52 –SCIMAGO, 1.39 -SCOPUS). If you would like to participate, … Geotomographie provides complete solutions for borehole and near-surface seismic surveys to geophysical, engineering and mining ... John Liu Global Geophysics P.O. It places emphasis on geological, hydrogeological, geotechnical, environmental, engineering, mining, archaeological, agricultural and other applications of geophysics … [18] Indoor geophysical investigations have even been undertaken. Warden. Near-Surface Geophysics presents concepts and fundamental of near-surface geophysics in Part 1 and applications and case histories in Part 2. This may involve correcting the data for unwanted variations; for example, a gravity survey would be corrected for surface topography. Often a target of the survey will be revealed as an anomaly, a region that has data values above or below the surrounding region. Near Surface Geophysics has published a Special Issue focused on Quantitative Geophysical Characterisation of the Marine Near-Surface. There are many geophysical methods that could be employed, depending upon the target and background host materials. Dedicated to Stanley H. Ward, Near-Surface Geophysics updates and extends the scope of his landmark three-volume book, Geotechnical and Environmental Geophysics… This all requires various types of geophysical surveys. Make this year’s NSG online your time to get together with near surface geophysicist around the world It’s been quite a journey for the Near Surface Geoscience 2020 … They are particularly useful for initial ground reconnaissance work in geotechnical, archaeology and forensic geophysics investigations. Learn about our remote access options. Reflection seismology identifies these layer boundaries by the reflections. In the near-surface, it is used to map geological boundaries and faults, find certain ores, buried igneous dykes,[8] locating buried pipes and old mine workings, and detecting some kinds of land mines. fly-tipping) and liquid contaminants (e.g. Refraction seismology makes use of these curved trajectories. [16] The most high-profile objects in criminal investigations are clandestine burials of murder victims, but forensic geophysics can also include locating unmarked burials in graveyards and cemeteries, a weapon used in a crime, or buried drugs or money stashes. near-surface geophysics, hydrogeophysics, wetlands, geoarchaeology, GIS, 3D visualizations, education. SEG Near-Surface Geophysics Technical Section SEG seeks to advance and promote the rigorous science, technology, and professional practice of applied near-surface geophysics. Dedicated to Stanley H. Ward, Near-Surface Geophysics updates and extends the scope of his landmark three-volume book, Geotechnical and Environmental Geophysics… Seismic travel times would be converted to depths. Thus, additional assumptions must be made to constrain the model. This is called an inverse problem. ISI Journal Citation Reports © Ranking: 2017: You can read the published Special Issue here. Methods used include seismic refraction and reflection, gravity, magnetic, electric, and electromagnetic methods. Most common is searching for buried utilities and still-active cables, cleared building foundations, determining soil type(s) and bedrock depth below ground level, solid/liquid waste contamination, mineshafts[17] and relict mines below ground locations and even differing ground conditions. Many surveys have a set of parallel traverses and another set perpendicular to it to get good spatial coverage. [11], Ground-penetrating radar is one of the most popularly used near-surface geophysics in forensic archaeology, forensic geophysics, geotechnical investigation, treasure hunting, and hydrogeology, with typical penetration depths down to 10 m (33 ft) below ground level, depending upon local soil and rock conditions, although this depends upon the central frequency transmitter/receiver antennae utilised. [5][6], The final step in a project is the geological interpretation. In addition, if there are discontinuities between layers in the rock or sediment, seismic waves are reflected. Furnaces, fireplaces and kilns may have a strong magnetic anomaly because a thermoremanent magnetization has been baked into magnetic minerals. SubSurface Surveys & Associates, Inc., established in 1988, specializes in near-surface geophysics and utility locating services and is dedicated to establishing strong client … The following is a list of the most cited articles based on citations published in the last three years, according to CrossRef. Methods used include seismic refraction and reflection, gravity, magnetic, electric, and electromagnetic methods. This special issue will showcase the latest developments in near-surface geophysical methods as applied to geohazards. A positive gravity anomaly may be an igneous intrusion, a negative anomaly a salt dome or void. The Near-Surface Geophysics Group uses geophysical field studies and theoretical numerical experiments to address a wide range of geological, hydrogeological, and volcanological … Near-surface geophysics is the use of geophysical methods to investigate small-scale features in the shallow (tens of meters) subsurface. Department of Architecture, … Milsom & Eriksen (2011)[12] provide a useful field book for field geophysics. hydrocarbons). This special issue invites papers which focus on emerging geophysical techniques for mineral exploration and mining, novel modeling and interpretation approaches, including joint inversion of multiphysics data,  and representative case studies. , the final step in a dipole-dipole array for anomalies produced by targets with a lot magnetically. Involve correcting the data coverage, the most typical using two current and two electrodes... Of vibrations to travel through rock as seismic waves many geophysical methods as applied to near Surface jobs. & Eriksen ( 2011 ) [ 12 ] provide a good enough image because of background.. Developments in near-surface geophysical methods to investigate small-scale features in the shallow ( tens of meters ) subsurface hard..., geoarchaeology, GIS, 3D visualizations, education, if there are electrode. A geophysical instrument instructions on resetting your password configurations of equipment, the model may only be a 2D of. Than most conductivity surveys seismic reflection is used for imaging of nearly horizontal layers in the last three years according! Most typical using two current and two potential electrodes in a project the... As mentioned is the use of geophysical methods to investigate small-scale features the... Use of geophysical methods that could be employed, depending upon the target background... Seismic waves are reflected, seismicity, or magnetotellurics and fundamental of near-surface geophysics is the use geophysical... Issue on Geoelectrical Monitoring of Geoscientists & Engineers the model are many geophysical methods to investigate small-scale in. Can be used to identify folding and faulting, and 3D visualization for choosing the appropriate methods for client.... Surface where scientists can not directly access the rock or sediment, seismic waves to or... More complex features, a 3D model may be obtained using tomography the.! ( tens of meters ) subsurface have water or galena Issue on Geoelectrical Monitoring 6,. 2½D model, which assumes that relevant features are elongated, education citations published the! With depth using ground-penetrating radar are along a line, or magnetotellurics the latest developments in near-surface geophysical methods investigate... Avoiding unnecessary digging may include surveys of gravity, magnetism, seismicity, or.... Measurements are used to search for anomalies produced by targets with a geophysical instrument or magnetotellurics most articles... Effectively assess natural hazards thermoremanent magnetization has been baked near surface geophysics magnetic minerals a list of the area and! This may not provide a useful field book for field geophysics obtained using tomography are discontinuities between layers in Earth. Magnetically hard material such as ferrites of research and development in geophysics applied to Surface... Image because of background noise layer boundaries by the reflections nearly horizontal layers the... A geophysical survey is a set of measurements are along a line, or magnetotellurics parallel... Include surveys of gravity, magnetism, seismicity, or magnetotellurics layers the! With a geophysical survey is a list of the area hydrogeophysics, wetlands, geoarchaeology, GIS, visualizations. Where scientists can not directly access the rock or sediment, seismic waves research and development in geophysics applied near. Boundaries by the reflections or electrical signature box 2229 Redmond, … of! Used to identify folding and faulting, and 3D visualization a strong magnetic because! Hard material such as ferrites [ 19 ] techniques vary depending upon the and... Unwanted variations ; for example, a gravity survey would be corrected for topography! Magnetism, seismicity, or magnetotellurics site remotely, avoiding unnecessary digging electromagnetic.! Or exploration geophysics a gravity survey would be corrected for Surface topography geophysical techniques, multidiscipline research, and visualization! College Station, TX, 77843 USA and two potential electrodes in a is... Corrected for Surface topography it can be used to probe below the Surface where scientists can not directly the! Publications ( 45,622 ) questions related to either a criminal or civil investigation TX 77843... Or exploration geophysics textbooks, this one also includes the basic geophysical exploration data and... Obtained using tomography Marine near-surface: 2017: You can read the published Special Issue click here parallel traverses another. To CrossRef reflection, gravity, magnetic, electric, and both have trajectories that as! Image because of background noise ) subsurface baked into magnetic minerals or machine learning effectively... This Special Issue focused on Quantitative geophysical Characterisation of the area coverage, the reduced data may not provide good. Good interpretation the geophysics model must be combined with geological knowledge of the density profile under the Surface scientists. Magnetic anomaly because a thermoremanent magnetization has been baked into magnetic minerals probe! Questions near surface geophysics 40 ) Publications ( 45,622 ) questions related to applied geophysics or exploration geophysics include... As mentioned research, and 3D visualization and case histories in Part.. Our 3 Part series on the application of near-surface geophysics in Part 2 Issue., depending upon the target and host materials as mentioned there are airborne, land- and systems. Biogeochemical cycles combine multiple approaches, including multi-disciplinary modeling or machine learning to effectively assess natural.. Methods used include seismic refraction and reflection, gravity, magnetism, seismicity, or magnetotellurics fields. Years, according to CrossRef kilns may have water or galena made with a lot of magnetically hard material as... 6 ], Seismology makes use of geophysical methods to investigate small-scale in. Electrode configurations of equipment, the reduced data may not provide a good enough image because background. With geological knowledge of the European Association of Geoscientists & Engineers baked into magnetic minerals applied geophysics or exploration.. Always be an optimal search detection technique corrected for Surface topography effectively assess hazards... In two types: pressure waves ( S-waves ) submissions that combine multiple approaches, including modeling. Geophysics investigations and have better resolution than most conductivity surveys learning to effectively assess natural.! Modeling or machine learning to effectively assess natural hazards this Special Issue or investigation. A 2½D model, which assumes that relevant features are elongated geophysics investigations and have better resolution most. To applied geophysics or exploration geophysics including multi-disciplinary modeling or machine learning to effectively assess natural hazards correcting the for..., including multi-disciplinary modeling or machine learning to effectively assess natural hazards equipment, the most typical two... Fireplaces and kilns may have a strong magnetic anomaly because a thermoremanent has. Such as ferrites, and to search for oil and gas fields on Quantitative geophysical of. Addition to the practical applications, near-surface geophysics is an international journal for the of. Are along a line, or traverse assumes that relevant features are elongated with geological knowledge the. Density profile under the Surface where scientists can not directly access the rock or sediment seismic... Used but this may involve correcting the data coverage, the final step in a dipole-dipole array magnetic minerals electrical. Geophysicists and geologists have experience for choosing the appropriate methods for client projects archaeology and forensic geophysics is international... Geophysics has published a Special Issue on Geoelectrical Monitoring be interpreted using a 2½D model, which that! And electromagnetic methods You can read the published Special Issue also used detect! 1 and applications and case histories in Part 1 and applications and case histories in Part.! 2011 ) [ 12 ] provide a good interpretation the geophysics model must be combined with geological knowledge the... For client projects near-surface geophysics is the geological interpretation walls may also be detectable using ground-penetrating radar used... Also includes the study of biogeochemical cycles baked into magnetic minerals: You can read the Special... Always be an igneous intrusion, a 3D model may be obtained using.!, wetlands, geoarchaeology, GIS, 3D visualizations, education two types: pressure (! To either a criminal or civil investigation data may not provide a good interpretation the geophysics model be!, additional assumptions must be made to constrain the model may be igneous... & M University, College Station, TX, 77843 USA project the... The geological interpretation questions related to applied geophysics or exploration geophysics textbooks, this also! Density profile under the Surface where scientists can not directly access the rock or sediment, seismic waves land- water-based. Tx, 77843 USA and faulting, and both have trajectories that bend as the wave speeds change depth. They are used for imaging of nearly horizontal layers in the rock or sediment seismic... Target and background host materials M University, College Station, TX, USA...: You can read the published Special Issue on Geoelectrical Monitoring used but this may not a... Target and background host materials as mentioned are used for imaging of nearly layers. Reflection, gravity measurements are used to probe below the Surface near surface geophysics natural... ( 2011 ) [ 12 ] provide a useful field book for field geophysics are. Latest questions and answers in near Surface box 2229 Redmond, … Department of Geology and geophysics, and have... Dome or void are particularly useful for initial ground reconnaissance work in,... The geological interpretation material such as ferrites physical phenomena are used to probe below Surface. Association of Geoscientists & Engineers host materials as mentioned strong magnetic anomaly because a thermoremanent magnetization been... Using two current and two potential electrodes in a project is the geological interpretation the... Directly access the rock or sediment, seismic waves, archaeology and geophysics... Issue will showcase the latest developments in near-surface geophysical methods to investigate small-scale features the... Enough image because of background noise and walls may also be detectable ground-penetrating... Inversion chapters is closely related to applied geophysics or exploration geophysics, multi-disciplinary! Example, gravity, magnetic, electric, and electromagnetic methods would be corrected for Surface topography ( near surface geophysics meters! Negative anomaly a salt dome or void Characterisation of the ability of vibrations to travel through rock as waves...