Reflection Of Seismic Waves Research Articles

Research on Tomography by Using Seismic Reflection Wave in Laneway

As a necessary step and an integral part of works in laneway, the geological prediction is an important means of reducing disaster losses and geological disasters in the works in laneway. This paper mainly discusses tunnel reflection tomography by using seismic reflection wave in laneway. The speed of elastic wave in front of tunnel face and the three-dimensional images can be figured out when the detector check the reflection of elastic wave from the focal points on the tunnel face. The location, size and depth of cave can be ascertained. According to the forecasts of laneway works in the Iron Mine Xishimen, tunnel reflection tomography by using seismic reflection wave can well forecast engineering geology and hydro-geological conditions in front of tunnel face. It will help to supply positive guidance for working plan and construction measures in laneway. Therefore, the construction safety and speed can be ensured, helping to lead to great practical significance and significant economic benefits.

Jacobian matrix for the inversion of P- and S-wave velocities and its accurate computation method

The optimization inversion method based on derivatives is an important inversion technique in seismic data processing, where the key problem is how to compute the Jacobian matrix. The computation precision of the Jacobian matrix directly influences the success of the optimization inversion method. Currently, all AVO (Amplitude Versus Offset) inversion techniques are based on approximate expressions of Zoeppritz equations to obtain derivatives. As a result, the computation precision and application range of these AVO inversions are restricted undesirably. In order to improve the computation precision and to extend the application range of AVO inversions, the partial derivative equation (Jacobian matrix equation (JME) for the P- and S-wave velocities inversion) is established with Zoeppritz equations, and the derivatives of each matrix entry with respect to P- and S-wave velocities are derived. By solving the JME, we obtain the partial derivatives of the seismic wave reflection coefficients (RCs) with respect to P- and S-wave velocities, respectively, which are then used to invert for P- and S-wave velocities. To better understand the behavior of the new method, we plot partial derivatives of the seismic wave reflection coefficients, analyze the characteristics of these curves, and present new understandings for the derivatives acquired from in-depth analysis. Because only a linear system of equations is solved in our method, the computation of Jacobian matrix is not only of high precision but also is fast and efficient. Finally, the theoretical foundation is established so that we can further study inversion problems involving layered structures (including those with large incident angle) and can further improve computational speed and precision.

Deep mantle plumes and convective upwelling beneath the Pacific Ocean

Earth's mantle is thought to convect as a whole, with material flow across the upper mantle phase transitions of the mineral olivine at 410 and 660 km depth. However, the details of convection, especially mantle upwelling and plumes, are not well constrained. Here, we study seismic shear wave reflections from the underside of these temperature and composition dependent phase boundaries, which we resolve to be relatively flat beneath most of the Pacific, except under subduction regions and volcanic hotspots. The phase boundaries are closer together beneath the Hawaiian hotspot and also in a larger region of the South Pacific that is flanked by a number of volcanic hotspots. This region overlies the southern part of the large-scale low shear velocity province in the lowermost mantle. A large plume head or cluster of several plumes originating in the lowermost mantle and impinging upon the South Pacific 660 km discontinuity is consistent with observed phase boundary topography and subduction patterns. This feature may be related to large volume volcanic eruptions, such as the Cretaceous Ontong Java Plateau flood basalts, which have been proposed to originate in the South Pacific.

Preface to the Special Issue on Potential Geohazards of the Taipei Metropolitan Area

The Taipei metropolitan area is located within a complex tectonic environment where several types of geohazards may readily occur. In order to better characterize and understand the tectonic environment and related surface processes that may threaten the residents of Taipei, the Taiwan Central Geological Survey launched a then newly integrated project a few years ago aimed at gathering up-todate tectonic, volcanic, seismic, geologic and geochemical data in the northern and offshore Taiwan. Many new and exciting findings have arisen from such a program and have provided further insight into the overall sources of geologic and seismic hazards around the Taipei metropolitan area. Earthquake threats for the Taipei metropolitan area come from several potential sources, including large earthquakes with epicenters located some distance from Taipei for example, the 921 Chi-Chi earthquake and earthquakes occurring offshore Hualien. If certain crustal conditions develop at the plate interface underneath the Taipei Basin and allow a reflection of seismic waves into the Taipei region, earthquakes can cause severe surface vibration resulting in serious damage. Another possible earthquake threat comes from fault activities at shallow depths such as the Shanchiao normal fault. Because most of the Taipei metropolitan area is located upon the soft Quaternary sediments of the geometrically complex Taipei Basin, it is important to better understand the physical properties of the basin sediment for seismic wave propagations. Several papers in this special issue address related issues of seismic wave properties and site responses in the Taipei metropolitan area. Furthermore, active volcanoes may also result in serious damage to society and surrounding environs as documented by numerous hazardous eruptions worldwide. Although no historical volcanic eruptions have been recorded in the Taiwan region, empirical and phenomenal evidence indicates that the Tatun volcano group and the Kueishantao volcanic island may include active volcanoes raising the critical question of how to evaluate the activities and threats of the volcanoes in Tatun and Kueishantao. Several papers address these questions in this issue to better characterize the status of volcanic activities and underlying processes. Here: Chen et al. (2010b) examine Holocene activities of the Shanchiao Fault by compiling sedimentary records, particularly depositional facies and available age dates of three boreholes in the Taipei Basin. The depositional history of the Taipei Basin since the Last Glacial Maximum can be quite well reconstructed using a simple back-stripping method. They point out tectonic subsidence events that may possibly be related to major earthquakes and suggest further studies of the fault activities are needed to explore other possibilities of earthquake events. Here Cheng et al. (2010) use available data to evaluate probabilistic seismic hazards including the attenuation relationship of the peak ground acceleration, fault-slip data, and seismicity. Important earthquake sources are pointed out in the metropolitan Taipei area. In addition to the long return earthquake period of active faults, the study calls for attention to the threats of high peak acceleration resulting from subduction zone earthquakes beneath the Taipei area. Recent surface deformation and changes may be monitored by new satellite-borne and airborne remote sensing techniques, particularly InSAR and LiDAR. Chang et al. (2010a) apply DInSAR and PSInSAR techniques to analyze the general uplift and subsidence pattern in northern Taiwan and show regions of surface change of the past decade as related to fault activities. Meanwhile, Chang et al. (2010b) present the mapping results of the Nankan lineament, which is considered to be an active fault as outlined by the Taiwan Central Geologic Survey, using the newly-derived airborne LiDAR topographic data and concludes that the lineament has not been tectonically active since the deposition of the alluvial fans, thus posing less threat to the Taipei area. Huang et al. (2010a) reconstruct two-dimensional motions of the magnitude 7.1 earthquake that occurred offshore eastern Taiwan in 2002 based on 89 free-field strong motion records in northern Taiwan. According to the study, seismic wave amplifications are obvious within the Taipei Basin, especially where the sediment is the thickest. Studying the same earthquake, Huang et al. (2010c) find that seismic waves travel within the Taipei Basin and have been reflected back from its western edge with a dominant frequency of about one Hz. Characterization of these seismic waves within the Taipei Basin should provide further information for prevention of shaking-induced hazards and importantly more realistic modeling of seismic propagation. Terr. Atmos. Ocean. Sci., Vol. 21, No. 3, I-III, June 2010

The Kupa Valley (Croatia) Earthquake of 8 October 1909--100 Years Later

The Kupa Valley (Croatia) earthquake of 8 October 1909 belongs to a group of milestone events in the history of geophysics and seismology. Also known as the Kulpa Valley, Pokuplje or the Pokupsko earthquake, it is often mentioned in textbooks, encyclopedias, and historical overviews of science as the earthquake whose seismograms provided key data for Andrija Mohorovicic's proof of the existence of the crust-mantle boundary that was later named after him. The earthquake occurred at just the right time and place to inspire research that resulted in one of the most-cited seismological papers (Mohorovicic 1910a, 1910b, 1910c) from the beginning of the last century. The paper itself was remarkable, as it contained much more than just the discovery it is mostly known for (see, e.g. , Herak and Herak 2007). As Kanamori (1986) noted in his Seismological Society of America presidential address, “having been motivated by this finding, Mohorovicic made an extensive study on reflection and refraction of seismic waves at a discontinuity to strengthen his conclusion. In fact, his study of this problem seems to have as strong an impact on seismology as his discovery of the discontinuity itself.” The time was right because the theory had been there for a long time, but the instruments had just gotten good enough to record seismograms with the needed detail. In particular, the Kupa Valley earthquake occurred only a year after the first Wiechert seismograph replaced the Vicentini instrument at the Zagreb observatory, which was already equipped with the first-class Riefler clock. The place was right because the earthquake occurred close to Zagreb (about 30 km to the south) where Mohorovicic lived, and it was strong enough to cause some damage in the city. Earthquakes had been of interest in Zagreb for some time, as seismicity around the capital …

Two Dimensional Common Reflection Surface Stack Based on the Fresnel Zone

AbstractCommon Reflection Surface (CRS) stack can improve signal‐to‐noise ratio of seismic signals. However, the key issue to improve resolution is how to set CRS stack aperture. In this paper, we discuss the characteristics of Fresnel zone during the reflection of seismic waves and suggest that the Fresnel zone under undulate layerinterface condition can be approximated with ellipse. Then we bring forward a method to determine the aperture size of CRS stack based on Fresnel zone and use it to deal with seismic section of the steep slope belt in Miyang Depression. The results show that Fresnel zone based CRS stack improves both the signal‐to‐noise ratio and resolution because the stacking aperture determined by Fresnel zone maximizes the superposition energy of seismic signals. In addition, deep weak seismic information is preserved and displayed, while normal CRS stack can only improve the signal‐to‐noise ratio and the shallow seismic information.

Constraining the anisotropy structure of the crust by joint inversion of seismic reflection travel times and wave polarizations

In the context of wide-angle seismic profiling, the determination of the physical properties of the Earth crust, such as the elastic layer depth and seismic velocity, is often performed by inversion of P- and/or S-phases propagation data supplying the geometry of the medium (reflector depths) or any other structural parameter (P- or S-wave velocity, density...). Moreover, the inversion for velocity structure and interfaces is commonly performed using only seismic reflection travel times and/or crustal phase amplitudes in isotropic media. But it is very important to utilize more available information to constrain the non-uniqueness of the solution. In this paper, we present a simultaneous inversion method of seismic reflection travel times and polarizations data of transient elastic waves in stratified media to reconstruct not only layer depth and vertical P-wave velocity but also the anisotropy feature of the crust based on the estimation of the Thomsen’s parameters. We carry out a checking with synthetic data, comparing the inversion results obtained by anisotropic travel-time inversion to the results derived by joint inversion of seismic reflection travel times and polarizations data. The comparison proves that the first procedure leads to biased anisotropic models, while the second one fits nearly the real model. This makes the joint inversion method feasible. Finally, we investigate the geometry, P-wave velocity structure and anisotropy of the crust beneath Southeastern China by applying the proposed inversion method to previously acquired wide-angle seismic data. In this case, the anisotropy signature provides clear evidence that the Jiangshan-Shaoxing fault is the natural boundary between the Yangtze and Cathaysia blocks.

Reflection of seismic surface waves at the northern Apennines

Seismic surface waves with periods of 15 to 20 s are reflected laterally at the northern Apennines. For earthquakes originated and recorded in the wider Alpine area, a few hundred kilometres north of the Apennines, we can directly observe late arrivals of reflected regional surface waves. These have a characteristic polarization of particle motion and often dominate the intermediate-period surface wave coda. Love waves are the most prominent coda arrivals, while reflected Rayleigh waves show smaller amplitudes, and become clear only after rotation of the recordings to the reflection incidence direction. We can track the development of the Love wave reflection along a temporary broad-band transect across the northern Apennines, indicating the location of the reflector near to the highest topography. From spectral element simulations of three-dimensional wave propagation, we attribute the reflection to a continuous, ∼ 270 km long offset in the crust-mantle boundary under the mountain belt with vertical throw of ∼ 20 km, thus supporting a deep crustal root under the outer side of the Apennines fold and thrust belt, and significant crustal thinning on the inner side. Amplitude reflection coefficients for near-normal incidence can be estimated as ∼ 7% for both Love and Rayleigh waves.

Artificial screen for reducing seismic vibration generated by blasting

The purpose of blasting operations is rock fragmentation. Blasting is a key component in the overall rock fragmentation system - the first element of the ore extraction process. It provides appropriate rock material granulation or size that is suitable for loading and transportation. However, in spite of many advantages explosives have, their usage may cause environmental problem such as seismic vibration. One of the solutions to this particular problem may be application of an artificial screen as a barrier to the seismic wave path. The results of experimental research on the artificial screen concept, its characteristics and role in attenuation of seismic effects generated by blasting are presented. The experiment is based on two physical phenomena: (1) the size and degree of discontinuity and (2) the reflection and refraction of seismic waves. More than 1,500 laboratory measurements were conducted with different combinations of screen sizes, positions of the screen to blasting source, and intensities of blasting impulses. The results of the study show reduction of generated vibrations up to 58% by employment of artificial screens.

Research and Analysis of Forward Prediction Technology Using Seismic Reflection Wave in Tunnel and Laneway in China

The detection and forecast for geological structure ahead of the tunnel and laneway is a very difficult problem in the world.Many applied researches based on the method of the seismic reflection wave have been done in our country from 1990,and many successful practical examples are obtained.At the same time,the detecting methods also have different problems.The main methods using reflection wave principle for forward prediction in the word include different forms,such as TSP,negative watching velocity,HSP,TRT,ISIS,and landsonar method,and so on.This article illustrates briefly the principle of different methods,and analyzes the status-quo of application and research of the forward prediction technology in China.The existing shortage in data collecting and processing of forward prediction ahead of tunnel and laneway is pointed out.The authors believe that the researches of the forward model and inversion theory,data collecting system in 3D complex space,migration imaging technology,etc,should be concerned in forward prediction and forecast.The aim of forward prediction is to establish and consummate the dynamic system of real time watching and forecasting for geological structures ahead of tunnel and laneway.

Discovery of a magma chamber and faults beneath a Mid-Atlantic Ridge hydrothermal field

Crust at slow-spreading ridges is formed by a combination of magmatic and tectonic processes, with magmatic accretion possibly involving short-lived crustal magma chambers. The reflections of seismic waves from crustal magma chambers have been observed beneath intermediate and fast-spreading centres, but it has been difficult to image such magma chambers beneath slow-spreading centres, owing to rough seafloor topography and associated seafloor scattering. In the absence of any images of magma chambers or of subsurface near-axis faults, it has been difficult to characterize the interplay of magmatic and tectonic processes in crustal accretion and hydrothermal circulation at slow-spreading ridges. Here we report the presence of a crustal magma chamber beneath the slow-spreading Lucky Strike segment of the Mid-Atlantic Ridge. The reflection from the top of the magma chamber, centred beneath the Lucky Strike volcano and hydrothermal field, is approximately 3 km beneath the sea floor, 3-4 km wide and extends up to 7 km along-axis. We suggest that this magma chamber provides the heat for the active hydrothermal vent field above it. We also observe axial valley bounding faults that seem to penetrate down to the magma chamber depth as well as a set of inward-dipping faults cutting through the volcanic edifice, suggesting continuous interactions between tectonic and magmatic processes.

Quantifying uncertainties on the solution model of seismic tomography

Reflection tomography allows the determination of a propagation velocity model that fits the traveltime data associated with reflections of seismic waves in the subsurface. A least-squares formulation is used to compare the observed traveltimes and the traveltimes computed by the forward operator based on a ray tracing. The solution of this inverse problem is only one among many possible models. A linearized a posteriori analysis is then crucial to quantify the range of admissible models we can obtain from these data and the a priori information. The contribution of this paper is to propose a formalism which allows us to compute uncertainties on relevant geological quantities for a reduced computational time. Nevertheless, this approach is only valid in the vicinity of the solution model (linearized framework), complex cases may thus require a nonlinear approach. Application on a 2D real data set illustrates the linearized approach to quantify uncertainties on the solution of seismic tomography. Finally, the limitations of this approach are discussed.

Low Vp/Vs ratios in the crust and upper mantle beneath the Sea of Okhotsk inferred from teleseismic pMP, sMP, and sMS underside reflections from the Moho

Teleseismic ground motion recordings of deep earthquakes often contain clear seismic wave reflections from the free surface above the source (pP, sP, sS), with isolated precursors (pMP, sMP, and sMS) produced by underside reflections from the Moho (the crust‐mantle boundary) below the free surface reflection points. The waveforms of the depth phases and their precursors are readily modeled, providing constraints, for steep angles of incidence, on integrated two‐way crustal travel times and Moho shear and compressional impedance contrasts above deep earthquake source regions. We model surface reflection waveforms in stacks of three‐component, long‐period WWSSN and digital broadband seismograms for signals traversing the crust and upper mantle beneath the Sea of Okhotsk, which overlies deep earthquakes in the subducted Kurile slab. The crust beneath most of the Sea of Okhotsk is 19–25 km thick, indicating a submerged continental margin, with minor crustal thinning toward the Kuril back‐arc basin, where thin oceanic crust is found. Modeling pMP and sMS phases that sample the same subregion provides tight constraints on the Vp/Vs ratio in the crust and uppermost mantle (assuming common density structure and consistent crustal thickness for P and S waves); the absolute velocities are not constrained by the data. We find unusually low Vp/Vs ratios in the range 1.6–1.7 for the uppermost mantle under the Sea of Okhotsk and comparably low average Vp/Vs ratios for the crust in several regions. The presence of fluids and extensive silica enrichment, possibly involving low‐temperature veining, are viable explanations for the anomalous Vp/Vs ratios; this may represent an important process of continentalization taking place landward from the volcanic arc in subduction zones.

Frozen magma lenses

Data on the reflection of seismic waves reveal chambers of frozen magma below the Earth's crust, supporting the theory that the crust was generated by multiple magmatic bodies.

Integrated archaeological exploration using geophysical methods at Futenma area, Okinawa prefecture, Japan

The archaeology and history of Okinawa are receiving a great deal of public attention as the Okinawans attempt to define their cultural and political identity in the closing decade of the 20th century. In an attempt to explore some of the old ruins in the area of Futenma, an integrated geophysical survey had been conducted in the form of two and three dimensional geoelectrical resistivity, surface seismic wave and seismic reflection surveys. The interpretation results of geoelectric survey had identified three-layer structure, which consists of superficial low-resistivity layer that indicates filling of Shimajiri maaji followed by high-resistivity layer that indicates Ryukyu limestone, and low-resistivity layer that indicates Shimajiri mudstone group. Also clear-cut reflectors of seismic reflection lines with good continuity are identified. These reflectors considered to reveal the surface of Ryukyu limestone of archaeological remains. The result of the surface wave survey identified two-layer structure that consists of superficial layer of surface wave velocity (0.3 km/s) overlies a relatively high velocity layer (0.5 km/s). The low velocity layer is estimated to indicate filling of Shimajiri maaji, while the high velocity layer correlates Ryukyu limestone formation.From the results it was predicted that subsurface structures of ruins influence the result of exploration even if their sizes are not large. Therefore, characteristic patterns due to a certain ruin structure can be distinguished, by making comparison with the excavation findings. The soil covering Ryukyu limestone is relatively thin; however, ruin structures naturally exist in the sedimentation soil above the limestone. It is highly probable that, as we trace back to older time, the land surface would be closer in shape to the upper surface of Ryukyu limestone. Furthermore, the survey results showed that Ryukyu limestone itself is considered to be divided into fresh zone and weathered zone, which possibly has been erroded and is providing channels for the ground water flow including a doline.According to the results we obtained in this work, even though, geoelectrical resistivity technique is stand-alone for archaeological prospection, its integration with seismic methods, mainly Surface seismic wave, survey give successful results.

AVO and the nature of light

Most geophysicists working in the hydrocarbon exploration industry will have come across the famous Zoeppritz (1919) equations that govern the AVO (amplitude variation with offset) behavior of reflected seismic waves. That is how the refection coefficient changes with angle of incidence at the boundary of two horizontal layers with different VP/VS ratios. This set of equations was published many years before the advent of exploration reflection seismology and it might be helpful to shed some light, in more than a proverbial sense, on the background of their derivation. The era of AVO as a DHI for gas sands was ushered in by Ostrander (1982) who popularized the method as a hydrocarbon exploration tool. Since then, the interest in this technique has continued with multiple sessions at the SEG Annual Meeting, special issues of The Leading Edge, dedicated seminars, and specialized processing/interpretation packages. Koefoed(1955) and Bortfeld (1961) often are cited as pioneers who introduced the principles of AVO to applied geophysics. Less known, however, is an early application by Blut (1932) who calculated AVA (amplitude variation with angle) responses for various lithologies, including ice, overburden (clastic sediments), basalt, and granite by using the relationships derived by Zoeppritz. Practical background of Blut's work was the interpretation of recordings from quarry blasts. Because of the instrumental limitations of his time, these remained rather theoretical considerations since calculating the AVA response curves in the days of logarithm tables and slide rules was quite an achievement given the rather cumbersome algebra of the Zoeppritz equations. Despite these computational challenges, apart from a different sign convention, Blut's AVA curves fit quite well with curves derived by modern Zoeppritz solvers. Zoeppritz's original publication “On the reflection and transmission of seismic waves at discontinuites” focuses on earthquake seismology. It is one …

The physics and simulation of wave propagation at the ocean bottom

We investigate some aspects of the physics of wave propagation at the ocean bottom (ranging from soft sediments to crustal rocks). Most of the phenomena are associated to the presence of attenuation. The analysis requires the use of an anelastic stress‐strain relation and a highly accurate modeling algorithm. Special attention is given to modeling the boundary conditions at the ocean‐bottom interface and the related physical phenomena. For this purpose, we further develop and test the pseudospectral modeling algorithm for wave propagation at fluid‐anelastic solid interfaces. The method is based on a domain‐decomposition technique (one grid for the fluid part and another grid for the solid part) and the Fourier and Chebyshev differential operators. We consider the reflection, transmission, and propagation of seismic waves at the ocean bottom, modeled as a plane boundary separating an acoustic medium (ocean) and a viscoelastic solid (sediment). The main physical phenomena associated with this interface are illustrated, namely, amplitude variations with offset, the Rayleigh window, and the propagation of Scholte and leaky Rayleigh waves. Modeling anelasticity is essential to describe these effects, in particular, amplitude variations near and beyond the critical angle, the Rayleigh window, and the dissipation of the fundamental interface mode. The physics of wave propagation is investigated by means of a plane‐wave analysis and the novel modeling algorithm. A wavenumber–frequency domain method is used to compute the reflection coefficient and phase angle from the synthetic seismograms. This method serves to verify the algorithm, which is shown to model with high accuracy the Rayleigh‐window phenomenon and the propagation of interface waves. The modeling is further verified by comparisons with the analytical solution for a fluid‐solid interface in lossless media, with source and receivers away from and at the ocean bottom. Using the pseudospectral modeling code, which allows general material variability, a complete and accurate characterization of the seismic response of the ocean bottom can be obtained. An example illustrates the effects of attenuation on the propagation of dispersive Scholte waves at the bottom of the North Sea.

Method of high-density seismic imaging exploration and application samples

The paper introduces the method of high-density seismic imaging exploration, discusses its features different from conventional shallow seismic reflection wave technique, and illustrates the application effect of the method using three samples of engineering geological explorations on land and in water — exploration of underground cavity, location survey of sunk ship and investigation of channel silt depth.

Scale dependence of reflection and transmission coefficients

Well logs show that heterogeneities occur at many different depth scales. This study examines the effects of these heterogeneities on the propagation of seismic waves, and specifically the dependence of reflection and transmission on the spatial scale content of the medium. Wavelet transformations are used to filter certain spatial scales from an acoustic sonic log. The scale‐filtered logs are used to construct layerstack models for which reflection and transmission seismograms are computed. The modified logs are also used to calculate frequency dependent reflection and transmission coefficients as functions of scale content. It is observed that features shorter than one‐fourth of the dominant wavelength have little effect on the reflection and transmission of seismic waves. Features larger than the dominant wavelength affect arrival times of individual packets within the wavetrain, but often these features hardly alter the overall appearance of individual wave packets. Reflection and transmission coda are primarily governed by heterogeneity at spatial scales similar to half the propagating wavelength. These scales appear to control the presence and shape of the events within the coda. The study also shows that the arrival times of packets at 1 kHz approach the theoretically expected value obtained from the harmonic velocity average, and the arrival times of packets below 1 Hz approach the theoretical value expected for the Backus average of the velocities.

Low‐cost geophysical investigations of a paleochannel aquifer in the Eastern Goldfields, Western Australia

Compressional (P) wave and shear (S) wave seismic reflection techniques were used to delineate the sand and gravel aquifer within a highly saline clay‐filled paleochannel in the Eastern Goldfields of Western Australia. The seismic refraction and gravity methods were also used to investigate the paleochannel. The unsaturated loose fine‐grained sand up to 10 m in depth at the surface is a major factor in degrading subsurface imaging. The seismic processing needed to be precise, with accurate static corrections and normal moveout corrections. Deconvolution enhanced the aquifer and other paleochannel reflectors. P‐wave reflection and refraction layer depths had good correlation and showed a total of six boundaries: (1) water table, (2) change in velocity (compaction) in the paleochannel sediments, (3) sand and gravel aquifer, (4) red‐brown saprolite and green saprolite boundary, (5) weathered bedrock, and (6) unweathered bedrock. P‐wave explosive and hammer sources were found to have similar signal characteristics, and the aquifer and bedrock were both imaged using the hammer source. The deep shots below the water table have the most broadband frequency response for reflections, but stacking clear reflections was difficult. The S‐wave reflection results showed high lateral and vertical resolution of the basal saprolite clay, the sand and gravel aquifer, and very shallow clays above the aquifer. The S‐wave reflection stacking velocities were 10–20% of the P‐waves, increasing the resolution of the S‐wave section. The gravity data were modelled to fit the known drilling and P‐wave seismic reflection depths. The refraction results did not identify the top of bedrock, so refraction depths were not used for the gravity modeling in this highly weathered environment. The final gravity model mapped the bedrock topography beyond the lateral extent of the seismic and drilling data.