﻿<?xml version="1.0" encoding="utf-8"?><rss version="2.0"><channel><title>International Journal of Geophysics</title><link>http://www.hindawi.com</link><description>The latest articles from Hindawi Publishing Corporation</description><copyright>&amp;#169; 2012, Hindawi Publishing Corporation. All rights reserved.</copyright><item><title>An Experimental and Modeling Study on the Response to Varying Pore Pressure and Reservoir Fluids in the Morrow A Sandstone</title><link>http://www.hindawi.com/journals/ijgp/2012/726408/</link><description>In mature oil fields undergoing enhanced oil recovery methods, such as CO2 injection, monitoring the reservoir changes becomes important. To understand how reservoir changes influence compressional wave (P) and shear wave (S) velocities, we conducted laboratory core experiments on five core samples taken from the Morrow A sandstone at Postle Field, Oklahoma. The laboratory experiments measured P- and S-wave velocities as a function of confining pressure, pore pressure, and fluid type (which included CO2 in the gas and supercritical phase). P-wave velocity shows a response that is sensitive to both pore pressure and fluid saturation. However, S-wave velocity is primarily sensitive to changes in pore pressure. We use the fluid and pore pressure response measured from the core samples to modify velocity well logs through a log facies model correlation. The modified well logs simulate the brine- and CO2-saturated cases at minimum and maximum reservoir pressure and are inputs for full waveform seismic modeling. Modeling shows how P- and S-waves have a different time-lapse amplitude response with offset. The results from the laboratory experiments and modeling show the advantages of combining P- and S-wave attributes in recognizing the mechanism responsible for time-lapse changes due to CO2 injection.</description><Author>Aaron V. Wandler, Thomas L. Davis, and Paritosh K. Singh</Author><copyright>Copyright &amp;#xa9; 2012 Aaron V. Wandler et al. All rights reserved.</copyright></item><item><title>2D Model Study of CO2 Plumes in Saline Reservoirs by Borehole Resistivity Tomography</title><link>http://www.hindawi.com/journals/ijgp/2011/805059/</link><description>The performance of electrical resistivity tomography (ERT) in boreholes is studied numerically regarding changes induced by CO2 sequestration in deep saline reservoirs. The new optimization approach is applied to generate an optimized data set of only 4&amp;#x25; of the comprehensive set but of almost similar best possible resolution. Diverse electrode configurations (mainly tripotential &amp;#x3b1; and &amp;#x3b2;) are investigated with current flows and potential measurements in different directions. An extensive 2.5D modeling (&amp;#x3e;100,000 models) is conducted systematically as a function of multiparameters related to hydrogeology, CO2 plume, data acquisition and methodology. ERT techniques generally are capable to resolve storage targets (CO2 plume, saline host reservoir, and impermeable cap rock), however with the common smearing effects and artefacts. Reconstructed tomograms show that the optimized and multiply oriented configurations have a better-spatial resolution than the lateral arrays with splitting of potential and current electrode pairs between boreholes. The later arrays are also more susceptible to telluric noise but have a lower level of measurement errors. The resolution advance of optimized and multiply oriented configurations is confirmed by lower values for ROI (region of index) and residual (relative model difference). The technique acceptably resolves targets with an aspect ratio down to 0.5.</description><Author>Said A. al Hagrey</Author><copyright>Copyright &amp;#xa9; 2011 Said A. al Hagrey. All rights reserved.</copyright></item><item><title>Nonlinear Magnetoconvection in a Sparsely Packed Porous Medium</title><link>http://www.hindawi.com/journals/ijgp/2011/207123/</link><description>Linear and weakly nonlinear properties of magnetoconvection in a sparsely
packed porous medium are investigated. We have obtained the values of Takens-Bogdanov bifurcation points and codimension two bifurcation points by plotting
graphs of neutral curves corresponding to stationary and oscillatory convection
for different values of physical parameters relevant to magnetoconvection in a
sparsely packed porous medium near a supercritical pitchfork bifurcation. We
have derived a nonlinear two-dimensional Ginzburg-Landau equation with real
coefficients by using Newell-Whitehead (1969) method. The effect of the parameter
values on the stability mode is investigated and shown the occurrence of
secondary instabilities namely, Eckhaus and Zigzag instabilities. We have studied
Nessult number contribution at the onset of stationary convection. We have also
derived two nonlinear one-dimensional coupled Ginzburg-Landau-type equations
with complex coefficients near the onset of oscillatory convection at a supercritical
Hopf bifurcation and discussed the stability regions of standing and travelling
waves.</description><Author>A. Benerji Babu, Ragoju Ravi, and S. G. Tagare</Author><copyright>Copyright &amp;#xa9; 2011 A. Benerji Babu et al. All rights reserved.</copyright></item><item><title>Anomalous Geomagnetic Variations Possibly Linked with the Taiwan Earthquake (Mw=6.4) on 19 December 2009</title><link>http://www.hindawi.com/journals/ijgp/2011/848467/</link><description>On 19 December 2009, the eastern part of Taiwan at approximate depth of 45&amp;#x2009;km was struck by a strong earthquake (Mw=6.4). The epicenter was located about 20&amp;#x2009;km away from the Hualien (HLN) station in Taiwan. By analyzing data from the HLN station and Amami Oshima (AMA) in Japan as a remote reference, the geomagnetic east-west (D) and vertical (Z) components recorded at the HLN station are showing no correlation with those at the AMA station in December 2009. Anomalous variations of &amp;#x223C;10&amp;#8211;15&amp;#x2009;nT started about one week before the occurrence of the earthquake and lasted for about two weeks. Also, an enhanced ULF signal in the range of Pc 3 (10&amp;#8211;40&amp;#x2009;s) was observed a few days before the onset of the earthquake. Moreover, the polarization ratio (Z/H (north-south component)) of the Pc 3 amplitude at the HLN station decreased a few days preceding the earthquake. The mechanism behind these anomalous variations is not fully understood. However, we expect that crustal stress perturbations and underground conductivity changes associated with the earthquake played an important role for generating such observed geomagnetic variations.</description><Author>E. M. Takla, K. Yumoto, J. Y. Liu, Y. Kakinami, T. Uozumi, S. Abe, and A. Ikeda</Author><copyright>Copyright &amp;#xa9; 2011 E. M. Takla et al. All rights reserved.</copyright></item><item><title>Remote Detection of the Electric Field Change Induced at the Seismic Wave Front from the Start of Fault Rupturing</title><link>http://www.hindawi.com/journals/ijgp/2011/752193/</link><description>Seismic waves are generally observed through the measurement of undulating elastic ground motion. We report the remote detection of the Earth&amp;#39;s electric field variations almost simultaneously with  the start of fault rupturing at about 100&amp;#x2009;km from the fault region using a special electric measurement. The rare but repeated detection indicates that the phenomenon is real. The characteristic time of diffusion is almost instantaneous, that is, less than 1 second to travel 100&amp;#x2009;km, more than ten times faster than ordinary seismic P wave propagation. We suggest that the measured electric field changes are produced by the electrokinetic effect through increased pore water pressure of the seismic pulse. It is also suggested that the long range propagation is due to the surface wave mode confined near the interface of the different conductivity. The length scale of the finite strength of the electric field is 16&amp;#x2009;km, 160&amp;#x2009;km for electric conductivity of 0.01, 0.001, Sm&amp;#x2212;1, respectively. This phenomenon suggests a new seismic sensing method and a new earthquake early warning system providing more seconds of lead time.</description><Author>Yukio Fujinawa, Kozo Takahashi, Yoichi Noda, Hiroshi Iitaka, and Shinobu Yazaki</Author><copyright>Copyright &amp;#xa9; 2011 Yukio Fujinawa et al. All rights reserved.</copyright></item><item><title>Electromagnetic Anomalies around The Wenchuan Earthquake and Their Relationship with Earthquake Preparation</title><link>http://www.hindawi.com/journals/ijgp/2011/904132/</link><description>Electromagnetic precursors before the Wenchuan earthquake on May 12, 2008 were collected and summarized on the basis of related published papers. The relationship  between electromagnetic anomalies and different earthquake preparation stages was analyzed, and an entire seismic preparation process was constructed according to corresponding anomalies in different electromagnetic parameters. It is illustrated that stereo electromagnetic observation is useful in the understanding of earthquake preparation mechanism. It is inevitable that a lot of problems exist in anomaly distinguishing and coupling mechanism analysis, which needs further studies in future.</description><Author>Xuemin Zhang and Xuhui Shen</Author><copyright>Copyright &amp;#xa9; 2011 Xuemin Zhang and Xuhui Shen. All rights reserved.</copyright></item><item><title>Hydrological Excitation of Polar Motion Derived from GRACE Gravity Field Solutions</title><link>http://www.hindawi.com/journals/ijgp/2011/174396/</link><description>The influence of the continental water storage on the polar motion is not well known. Different models have been developed to evaluate these effects and compared to geodetic observations. However, previous studies have shown large discrepancies mainly attributed to the lack of global measurements of related hydrological parameters. Now, from the observations of the GRACE mission, we can estimate the polar motion excitation  due to the global hydrology. Data processing of GRACE data is carried out by several centers of analysis, we focus on the new solution computed by the Groupe de Recherche de G&amp;#233;od&amp;#233;sie Spatiale. At annual scales, excitations derived from GRACE data are in better agreement with geodetic observations than models estimates. The main contribution to the hydrological excitation comes from the monsoon climates regions where GRACE and models estimates are in a very good agreement. Still, the effect of the north high latitudes regions, where  the principal areas of snow cover are found, cannot be neglected. At these regions, GRACE and models estimated contributions to polar motion excitations show significant discrepancies. Finally, GRACE-based excitations reveal the possible influence of water storage variations in exciting polar motion around the frequency of 3 cycles per year.</description><Author>L. Seoane, J. Nastula, C. Bizouard, and D. Gambis</Author><copyright>Copyright &amp;#xa9; 2011 L. Seoane et al. All rights reserved.</copyright></item><item><title>Ground Penetrating Radar Assessment of  Flexible Road Pavement Degradation</title><link>http://www.hindawi.com/journals/ijgp/2011/989136/</link><description>GPR investigations were used to study degraded road pavements built in cutting sections. Road integrity was assessed via quantitative analysis of power curves. 1600&amp;#x2009;MHz and 600&amp;#x2009;MHz radar sections were collected in 40 damaged and undamaged road pavement sites. The collected data were processed as follows: (i) linearisation with regression analysis of power curves; (ii) assessment of absorption angle  &amp;#x03B1;&amp;#x2032; which is directly proportional to absorption coefficient  &amp;#x03B1; (this was obtained by setting the e.m. propagation velocity to 10&amp;#x2009;cm/ns); (iii) comparison of absorption coefficients in both damaged and undamaged zones with respect to road pavement degradation.
If the absorption coefficients of damaged and undamaged road sections have nearly the same value, then the likely cause of degradation is the fatigue or the thermal shrinkage; if they are not, then road degradation is due to the different compactness of the soil caused by vehicular traffic load. In a considerable number of sites, the statistical comparison of damaged and undamaged zones through the absorption coefficient analysis shows that surface observations of road pavements are quite consistent with power curve analyses.</description><Author>Sandro Colagrande, Danilo Ranalli, and Marco Tallini</Author><copyright>Copyright &amp;#xa9; 2011 Sandro Colagrande et al. All rights reserved.</copyright></item><item><title>Analysis of the Crust Deformations before and after the 2008 Wenchuan Ms8.0 Earthquake Based on GPS Measurements</title><link>http://www.hindawi.com/journals/ijgp/2011/802346/</link><description>We use the movement velocities of GPS stations in western Sichuan province, China, to determine the distribution of horizontal strain accumulation before the 2008 Wenchuan Ms8.0 earthquake with a piecewise approximation approach and the coseismic displacements to determine the fault slips of the earthquake with an inversion analysis method. The results show that the distribution of the principal strain rates is strongly related to the active faults in the region, but along Longmenshan fault where the earthquake occurred, the strain rates are much lower than the others. The fault slip distribution shows mainly a thrusting with dextral striking, and the fault slips in the upper parts of the fault plane are in general bigger. Using the current strain accumulation rate and the released energy by the earthquake, we predict such a big earthquake in Longmenshan fault zone will happen in 460 to 1380 years.</description><Author>Jicang Wu, Renzhao Liu, Yongqi Chen, Conrad Tang, Guojie Meng, and Yaming Dang</Author><copyright>Copyright &amp;#xa9; 2011 Jicang Wu et al. All rights reserved.</copyright></item><item><title>Latitude-Time Total Electron Content Anomalies as Precursors to Japan&amp;#39;s Large Earthquakes Associated with Principal Component Analysis</title><link>http://www.hindawi.com/journals/ijgp/2011/763527/</link><description>The goal of this study is to determine whether principal component analysis (PCA) can be used to process latitude-time ionospheric TEC data on a monthly basis to identify earthquake associated TEC anomalies. PCA is applied to latitude-time (mean-of-a-month) ionospheric total electron content (TEC) records collected from the Japan GEONET network to detect TEC anomalies associated with 18 earthquakes in Japan (M&amp;#x2265;6.0) from 2000 to 2005. According to the results, PCA was able to discriminate clear TEC anomalies in the months when all 18 earthquakes occurred. After reviewing months when no M&amp;#x2265;6.0 earthquakes occurred but geomagnetic storm activity was present, it is possible that the maximal principal eigenvalues PCA returned for these 18 earthquakes indicate earthquake associated TEC anomalies. Previously PCA has been used to discriminate earthquake-associated TEC anomalies recognized by other researchers, who found that statistical association between large earthquakes and TEC anomalies could be established in the 5 days before earthquake nucleation; however, since PCA uses the characteristics of principal eigenvalues to determine earthquake related TEC anomalies, it is possible to show that such anomalies existed earlier than this 5-day statistical window.</description><Author>Jyh-Woei Lin</Author><copyright>Copyright &amp;#xa9; 2011 Jyh-Woei Lin. All rights reserved.</copyright></item><item><title>Comparative Hydrological and Geoelectrical Study on the Quaternary Aquifer in the Deltas of Wadi Badaa and Ghweiba, El Ain El Sukhna Area, Northwest Suez Gulf, Egypt</title><link>http://www.hindawi.com/journals/ijgp/2010/585243/</link><description>El Ain El Sukhna area was selected in the last ten years to initiate many governmental and investmental programs. The different activities in that area depend mainly on the groundwater of the Quaternary aquifer, which forms the main water bearing strata. In the present work, twenty one geoelctrical soundings using the Schlumberger configuration are carried out at selected sites especially in missing parts from wells to delineate the groundwater setting in such sites. Eight of them are conducted in the close vicinity of water wells, where lithologs and pumping test data of these wells are available to relate hydrologic and geoelctric measurements. The pumping tests data are analyzed by using AQTESOLV program and the geolectrical sounding data were interpreted by partial curve matching technique to obtain the initial parameters. The results indicated that, the transmissivity is found to be closely related with transverse resistance and the hydraulic conductivity with average transverse resistivity, while the salinity is inversely related with resistivity. Finally, priority map for drilling water wells is constructed to make the results more illustrative and useful for decision maker. The promising area for drilling is located at the western portion of the study region.</description><Author>M. M. El Osta, A. El. El Sheikh, and M. S. Barseem</Author><copyright>Copyright &amp;#xa9; 2010 M. M. El Osta et al. All rights reserved.</copyright></item><item><title>Physics of Magnetopause Reconnection: A Study of the Combined Effects of Density Asymmetry, Velocity Shear, and Guide Field</title><link>http://www.hindawi.com/journals/ijgp/2010/202583/</link><description>Magnetopause reconnection would be characterized by the density jump across the current sheet, the flow shear across the boundary, and nonzero guide field. While effects of each of these elements have been studied, the effects arising from the combination of these are still unexplored. Two-dimensional full-particle simulations show that the combination of shear flow and/or guide field with density asymmetry induces the sliding motion of the X-line along the magnetopause. The direction of the X-line motion is controlled either by the ion flow at the X-line when the shear flow effects dominate or by the electron flow at the X-line when the guide field effects dominate. The shear flow effects and the guide field effects may counteract each other in determining the direction of the X-line motion and, in the close proximity of the subsolar region where the flow is slow, the X-line motion can be opposite to the flow direction.</description><Author>Kentaro G. Tanaka, Masaki Fujimoto, and Iku Shinohara</Author><copyright>Copyright &amp;#xa9; 2010 Kentaro G. Tanaka et al. All rights reserved.</copyright></item><item><title>The Postglacial Rebound Signal of Fennoscandia Observed by Absolute Gravimetry, GPS, and Tide Gauges</title><link>http://www.hindawi.com/journals/ijgp/2011/957329/</link><description>We have compiled time derivatives of gravity and vertical motion for a dozen sites in Fennoscandia. Time series of absolute gravimetry and permanent GPS cover a time span of about a decade. Tide gauges have operated for many decades near seven of the sites. Linear relations are found to range from &amp;#x2212;0.17 to &amp;#x2212;0.22 for the slope between gravity and vertical uplift rates. An eustatic sea level rate of 1.2&amp;#x2009;mm/year is derived from these data. This compares well with results for North America and with theoretical predictions for viscoelastic Earth models.</description><Author>Bj&amp;#248;rn Ragnvald Pettersen</Author><copyright>Copyright &amp;#x00A9; 2011 Bj&amp;#xf8;rn Ragnvald Pettersen. All rights reserved.</copyright></item><item><title>Electrical Resistivity Structure and Helium Isotopes around Naruko Volcano, Northeastern Japan and Its Implication for the Distribution of Crustal Magma</title><link>http://www.hindawi.com/journals/ijgp/2010/738139/</link><description>The two-dimensional electrical resistivity structure beneath Naruko volcano was determined using magnetotelluric soundings. The resulting model shows that a prominent conductor exists through the middle crust to the uppermost mantle beneath the volcano. The location of the conductor agrees closely with a seismic low-velocity zone. Low-frequency microearthquakes occur near the conductor around the Moho depth. The cutoff depth of crustal earthquakes is coincident with the upper boundary of the conductor, implying that the conductor has a temperature appreciably higher than 400&amp;#x2218;C. Furthermore, new helium isotope data from hot springs around the volcano were obtained. The spatial distribution of the observed H3e/H4e ratios reveals the extent of mantle-derived materials beneath Naruko volcano. Consequently, it is apparent that the conductor determined beneath the volcano reflects the presence of high-temperature mantle-derived materials such as magmas and/or related fluids derived from active magmatism in the northeastern Japan subduction zone.</description><Author>Koichi Asamori, Koji Umeda, Yasuo Ogawa, and Teruki Oikawa</Author><copyright>Copyright &amp;#xa9; 2010 Koichi Asamori et al. All rights reserved.</copyright></item><item><title>On the Efficiency of the Multi-Channel Analysis of Surface Wave Method for Shallow and Semi-Deep Loose Soil Layers</title><link>http://www.hindawi.com/journals/ijgp/2010/403016/</link><description>The multi-channel analysis of surface waves (MASWs) method was used to obtain the shear wave velocity variations through near surface (depth &amp;#60; 30&amp;#x2009;m) and semi-deep (30&amp;#x2009;m &amp;#60; depth &amp;#60; 100&amp;#x2009;m) soil layers in the city of Ottawa, Canada. Sixteen sites were examined to evaluate the capability of the active and passive MASW methods for cases where the shear wave velocity (Vs) contrast between very loose soil (Vs &amp;#60; 200&amp;#x2009;m/s) and very firm bedrock (Vs &amp;#62; 2,300&amp;#x2009;m/s) is very large. The MASW velocity results compared with those of other geophysical approaches, such as seismic reflection/refraction methods and borehole data, where available, mostly confirming the capability of the MASW method to distinguish the high shear wave velocity contrast in the study area. We have found that, of the inversion procedures of MASW data, the random search inversion technique provides better results than the analytical generalized inversion method.</description><Author>Kasgin Khaheshi Banab and Dariush Motazedian</Author><copyright>Copyright &amp;#x00A9; 2010 Kasgin Khaheshi Banab and Dariush Motazedian. All rights reserved.</copyright></item><item><title>A Magma Accretion Model for the Formation of Oceanic Lithosphere: Implications for Global Heat Loss</title><link>http://www.hindawi.com/journals/ijgp/2010/146496/</link><description>A magma accretion model of oceanic lithosphere is proposed and its implications for understanding its thermal field examined. The new model (designated Variable Basal Accretion&amp;#x02014;VBA) assumes existence of lateral variations in magma accretion rates and temperatures at the boundary zone between the lithosphere and the asthenosphere. However, unlike the previous thermal models of the lithosphere, the ratio of advection to conduction heat transfer is considered a space dependent variable. The results of VBA model simulations reveal that the thickness of the young lithosphere increases with distance from the ridge axis, at rates faster than those predicted by Half-Space Cooling models. Another noteworthy feature of the new model is its ability to account for the main features in the thermal behavior of oceanic lithosphere. The improved fits to bathymetry have been achieved for the entire age range and without the need to invoke the ad-hoc hypothesis of large-scale hydrothermal circulation. Also, use of VBA model does not lead to artificial discontinuities in the temperature field of the lithosphere, as is the case with GDH (Global Depth Heat Flow) reference models. The results suggest that estimates of global heat loss need to be downsized by at least 25&amp;#37;.</description><Author>Valiya M. Hamza, Roberto R. Cardoso, and Carlos H. Alexandrino</Author><copyright>Copyright &amp;#x00A9; 2010 Valiya M. Hamza et al. All rights reserved.</copyright></item><item><title>Three-Component Forward Modeling for Transient Electromagnetic Method</title><link>http://www.hindawi.com/journals/ijgp/2010/791790/</link><description>In general, the time derivative of vertical magnetic field is considered only in the data interpretation of transient electromagnetic (TEM) method. However, to survey in the complex geology structures, this conventional technique has begun gradually to be unsatisfied with the demand of field exploration. To improve the integrated interpretation precision of TEM, it is necessary to study the three-component forward modeling and inversion. In this paper, a three-component forward algorithm for 2.5D TEM based on the independent electric and magnetic field has been developed. The main advantage of the new scheme is that it can reduce the size of the global system matrix to the utmost extent, that is to say, the present is only one fourth of the conventional algorithm. In order to illustrate the feasibility and usefulness of the present algorithm, several typical geoelectric models of the TEM responses produced by loop sources at air-earth interface are presented. The results of the numerical experiments show that the computation speed of the present scheme is increased obviously and three-component interpretation can get the most out of the collected data, from which we can easily analyze or interpret the space characteristic of the abnormity object more comprehensively.</description><Author>Bin Xiong</Author><copyright>Copyright &amp;#x00A9; 2010 Bin Xiong. All rights reserved.</copyright></item><item><title>A Constrained 3D Density Model of the Upper Crust from Gravity Data Interpretation for Central Costa Rica</title><link>http://www.hindawi.com/journals/ijgp/2010/860902/</link><description>The map of complete Bouguer anomaly of Costa Rica shows an elongated NW-SE trending gravity low in the central region. This gravity low coincides with the geographical region known as the Cordillera Volc&amp;#225;nica Central. It is built by geologic and morpho-tectonic units which consist of Quaternary volcanic edifices. For quantitative interpretation of the sources of the anomaly and the characterization of fluid pathways and reservoirs of arc magmatism, a constrained 3D density model of the upper crust was designed by means of forward modeling. The density model is constrained by simplified surface geology, previously published seismic tomography and P-wave velocity models, which stem from wide-angle refraction seismic, as well as results from methods of direct interpretation of the gravity field obtained for this work. The model takes into account the effects and influence of subduction-related Neogene through Quaternary arc magmatism on the upper crust.</description><Author>Oscar H. L&amp;#252;cke, Hans-J&amp;#252;rgen G&amp;#246;tze, and Guillermo E. Alvarado</Author><copyright>Copyright &amp;#x00A9; 2010 Oscar H. L&amp;#252;cke et al. All rights reserved.</copyright></item><item><title>A Metastable Aluminosilica Compound for Aluminum and Water Transport to the Upper Mantle</title><link>http://www.hindawi.com/journals/ijgp/2009/909431/</link><description>It has been suggested that crystalline &amp;#8220;phase egg,&amp;#8221; AlSiO3OH, with a ratio Al/Si=1 could carry aluminum and water to the mantle but its natural occurrences are still speculative. An amorphous phase with a fixed and unique, deep metastable eutectic Al2Si2O7 composition was produced in laboratory experiments wherein conditions favored kinetically controlled formation of amorphous solids. This experimentally produced kaolinite-dehydroxylate is highly reactive and it is proposed as the precursor of phase egg in subducting slabs of crustal rocks. If so, metastable phases play a role in subduction zones and it then follows that the processes and resulting conditions in these environments can be nonuniform and discontinuous at least at micrometer scales.</description><Author>Frans J. M. Rietmeijer and Joseph A. Nuth III</Author><copyright>Copyright &amp;#x00A9; 2009 Frans J. M. Rietmeijer and Joseph A. Nuth III. All rights reserved.</copyright></item><item><title>The Edgerton Structure: A Possible Meteorite Impact Feature in Eastern Kansas</title><link>http://www.hindawi.com/journals/ijgp/2009/621528/</link><description>Recognized meteorite impact features are relatively rare in the U.S. Midcontinent region, but recently with increased interest and research, the number has increased dramatically. We add another possibility to the growing list, the Edgerton structure in northwestern Miami County, Kansas. The feature is elliptical (&amp;#x223C;5.5 &amp;#x00D7; 6.5&amp;#x2009;km, slightly elongated east-west) with radial surface drainage. The feature was first observed on hillshade maps of digitized topography of 7.5 minute quadrangles. Subsequent magnetic profiles show a higher magnetic value in the center of the ellipse with higher values around the edges; this shape is characteristic of an impact feature. Depth to the anomalous body is estimated to be about 1&amp;#x2009;km, which puts it in the Precambrian crystalline basement under a cover of Paleozoic sediments. There are no deep boreholes in the vicinity and no seismic profiles are available. If it is an impact structure, it will be the second such feature documented in Kansas, the first being the Brenham meteorite crater at Haviland in Kiowa County in southwestern Kansas. It would be older than the other impact structures identified in the Midcontinent&amp;#8212;Manson in Iowa, Ames in Oklahoma, Haswell Hole in Colorado, and possibly Belton in Missouri and Merna in Nebraska. There are at least two other prospective impact features in Kansas: the Goddard ring west of Wichita and Garden City ellipse north-west of Garden City.</description><Author>Daniel  F. Merriam, Jianghai Xia, and John W. Harbaugh</Author><copyright>Copyright &amp;#x00A9; 2009 Daniel  F. Merriam et al. All rights reserved.</copyright></item><item><title>Model-Based Identification of the Base of the Gas Hydrate Stability Zone in Multichannel Reflection Seismic Data, Offshore Costa Rica</title><link>http://www.hindawi.com/journals/ijgp/2009/812713/</link><description>Along the pacific margin offshore Costa Rica the Bottom Simulating Reflector (BSR) shows a patchy occurrence in 2-D seismic reflection profiles. The reason for this can be either lack of free gas beneath parts of the gas hydrate stability zone (GHSZ) or poor seismic imaging. We compare far to near offset stacked common midpoint sections to reduce imaging ambiguity utilizing the amplitude variation with offset effect and thus successfully distinguish BSRs from regular sediment reflections. In combination with 1-D modeling of the base of the GHSZ we disqualify or qualify reflections in the predicted depth range as BSR. Additionally we calculate the heat flow and compare it with an analytical solution to detect thermal anomalies, for example, at the frontal prism. The higher confidence in BSR depths based on the far offset stacks and heat flow calculations allows further analyses on gas hydrate concentration estimates and tectonic evolution of the margin.</description><Author>Romina Gehrmann, Christian M&amp;#252;ller, Peter Schikowsky, Thomas Henke, Michael Schnabel, and Christian B&amp;#246;nnemann</Author><copyright>Copyright &amp;#x00A9; 2009 Romina Gehrmann et al. All rights reserved.</copyright></item><item><title>Extensional Seismogenic Stress and Tectonic Movement on the Central Region of the Tibetan Plateau</title><link>http://www.hindawi.com/journals/ijgp/2009/897424/</link><description>Various earthquake fault types, mechanism solutions and stress fields, as well as GPS and geothermal data are analyzed for the study of the crustal movements on the Tibetan plateau and their tectonic implications. The results show that a lot of the normal faulting type-event concentrated at altitudes greater than 4000&amp;#x2009;m on the central Tibetan plateau. The altitudes concentrating normal faulting type-events can be zoned two parts: the western part, the Lhasa block, and the eastern part, the Qiangtang-Changdu region. The azimuths of T-axes are in a general E-W direction in the Lhasa block and NW-SE or NNW-SSE in the Qiangtang-Changdu region at the altitudes of the Tibetan plateau. The tensional stresses in E-W direction and NW-SE direction predominate normal faulting earthquake occurrence in the Lhasa block and the Qiangtang-Changdu region, respectively. The slipping displacements of the normal-faulting-type events have great components in near E-W direction and NW-SE direction in the Lhasa block and the Qiangtang-Changdu region, respectively. The extensions are probably an eastward or southeastward extensional motion, being mainly tectonic activity phenomena in the plateau altitudes. The extensional motions due to normal-fault earthquakes are important tectonic activity regimes on the high altitudes of the plateau. The easterly crustal extensions on the plateau are attributable to the gravitational collapse of the high plateau and eastward extrusion of hotter mantle materials beneath the eastern boundary of the plateau. Numbers of thrust-fault and strike-slip-fault earthquakes with strong compressive stress in a general NNE-SSW direction occur on the edges of the plateau.</description><Author>Jiren Xu and Zhixin Zhao</Author><copyright>Copyright &amp;#x00A9; 2009 Jiren Xu and Zhixin Zhao. All rights reserved.</copyright></item><item><title>A Comparative Analysis of Seismological and Gravimetric Crustal Thicknesses below the Andean Region with Flat Subduction of the Nazca Plate</title><link>http://www.hindawi.com/journals/ijgp/2009/607458/</link><description>A gravimetric study was carried out in a region of the Central Andean Range between 28&amp;#x2218; and 32&amp;#x2218; south latitudes 
 and from 72&amp;#x2218; and 66&amp;#x2218; west longitudes. The seismological and gravimetrical Moho models were compared in a sector which coincides with the seismological stations of the CHARGE project. The comparison reveals discrepancies between the gravity Moho depths and those obtained from seismological investigations (CHARGE project), the latter giving deeper values than those resulting from the gravimetric inversion. These discrepancies are attenuated when the positive gravimetric effect of the Nazca plate is considered. Nonetheless, a small residuum of about 5&amp;#x2009;km remains beneath the Cuyania terrane region, to the east of the main Andean chain. This residuum could be gravimetrically justified if the existence of a high density or eclogitized portion of the lower crust is considered. This result differed from the interpretations from Project &amp;#x201c;CHARGE&amp;#x201d; which revealed that the entire inferior crust extending from the Precordillera to the occidental &amp;#x201c;Sierras Pampeanas&amp;#x201d; could be &amp;#x201c;eclogitized&amp;#x201d;. In this same sector, we calculated the effective elastic thickness (Te) of the crust. These results indicated an anomalous value of Te = 30&amp;#x2009;km below the Cuyania terrane. This is further conclusive evidence of the fact that the Cuyania terrane is allochthonous, for which also geological evidences exist.</description><Author>Mario E. Gimenez, Carla Braitenberg, M. Patricia Martinez, and Antonio Introcaso</Author><copyright>Copyright &amp;#x00A9; 2009 Mario E. Gimenez et al. All rights reserved.</copyright></item><item><title>Magnetostratigraphy and Tectonic Rotation of the Eocene-Oligocene Makah and Hoko River Formations, Northwest Washington, USA</title><link>http://www.hindawi.com/journals/ijgp/2009/930612/</link><description>The Eocene-Oligocene Makah Formation and subjacent middle Eocene Hoko River Formation of the northwestern Olympic Peninsula, Washington, yield mollusks, crustaceans, foraminifera, and early neocete whales; their age has never been precisely established. We sampled several sections; most samples showed a stable single-component remanence held largely in magnetite and passed a Class I reversal test. The upper Refugian (late Eocene) and lower Zemorrian (early Oligocene) rocks at Baada Point correlate with Chron C13r (33.7&amp;#x02013;34.7 Ma) and Chron C12r (30&amp;#8211;33 Ma). The Ozette Highway section of the Makah Formation spanned the early Refugian to late Refugian, with a sequence that correlates with Chrons C15r-C13r (33.7&amp;#8211;35.3 Ma), and a long reversed early Zemorrian section that correlates with Chron C12r (30&amp;#8211;33 Ma). The type section of the Hoko River Formation correlates with Chron C18r (40.0&amp;#8211;41.2 Ma). The area sampled shows about 45&amp;#x2218; of post-Oligocene counterclockwise tectonic rotation, consistent with results obtained from the Eocene-Oligocene rocks in the region.</description><Author>Donald R. Prothero, Elizabeth Draus, and Casey Burns</Author><copyright>Copyright &amp;#x00A9; 2009 Donald R. Prothero et al. All rights reserved.</copyright></item><item><title>Modern Geodata Management: Application of Interdisciplinary Interpretation and Visualization in Central America</title><link>http://www.hindawi.com/journals/ijgp/2009/878324/</link><description>In the last years new methods of data acquisition and processing in geosciences, inspired by growing computer performance, have led to an increased amount of data, and this development will proceed surely. In this paper we present the conception and technical realization of an interdisciplinary research group&amp;#39;s geodata management as a combination of a metadata catalog together with web mapping technology. Clearly related with the storage and retrieval of different datasets is the need of visualization. 3D visualization in geoscientific interpretation is a useful tool, if numerous, heterogenic datasets have to be visualized at the same time. Moreover, advanced sensing technology often generates native three-dimensional datasets. Using a case study from the Collaborative Research Centre &amp;#8220;SFB 574&amp;#8221;, we present the possibilities of our stereoscopic projection system and want to explain the benefit of 3D visualization for research in general and university education in particular, as low-cost systems become available nowadays.</description><Author>T. Damm and H.-J. G&amp;#246;tze</Author><copyright>Copyright &amp;#x00A9; 2009 T. Damm and H.-J. G&amp;#246;tze. All rights reserved.</copyright></item><item><title>A Tsunami Ball Approach to Storm Surge and Inundation: Application to Hurricane Katrina, 2005</title><link>http://www.hindawi.com/journals/ijgp/2009/324707/</link><description>Most analyses of storm surge and inundation solve equations of continuity and momentum on fixed finite-difference/finite-element meshes. I develop a completely new approach that uses a momentum equation to accelerate bits or balls of water over variable depth topography. The thickness of the water column at any point equals the volume density of balls there. In addition to being more intuitive than traditional methods, the tsunami ball approach has several advantages. (a) By tracking water balls of fixed volume, the continuity equation is satisfied automatically and the advection term in the momentum equation becomes unnecessary. (b) The procedure is meshless in the finite-difference/finite-element sense. (c) Tsunami balls care little if they find themselves in the ocean or inundating land. (d) Tsunami ball calculations of storm surge can be done on a laptop computer. I demonstrate and calibrate the method by simulating storm surge and inundation around New Orleans, Louisiana caused by Hurricane Katrina in 2005 and by comparing model predictions with field observations. To illustrate the flexibility of the tsunami ball technique, I run two &amp;#8220;What If&amp;#8221; hurricane scenarios&amp;#8212;Katrina over Savannah, Georgia and Katrina over Cape Cod, Massachusetts.</description><Author>Steven N. Ward</Author><copyright>Copyright &amp;#x00A9; 2009 Steven N. Ward. All rights reserved.</copyright></item></channel></rss>
