Basis Of Geophysical Data Research Articles

Derivation and Error Analysis of the Earth Magnetic Anomaly Grid at 2 arc min Resolution Version 3 (EMAG2v3)

AbstractThe Earth Magnetic Anomaly Grid at 2 arc min resolution version 3, EMAG2v3, combines marine and airborne trackline observations, satellite data, and magnetic observatory data to map the location, intensity, and extent of lithospheric magnetic anomalies. EMAG2v3 includes over 50 million new data points added to NCEI's Geophysical Database System (GEODAS) in recent years. The new grid relies only on observed data, and does not utilize a priori geologic structure or ocean‐age information. Comparing this grid to other global magnetic anomaly compilations (e.g., EMAG2 and WDMAM), we can see that the inclusion of a priori ocean‐age patterns forces an artificial linear pattern to the grid; the data‐only approach allows for greater complexity in representing the evolution along oceanic spreading ridges and continental margins. EMAG2v3 also makes use of the satellite‐derived lithospheric field model MF7 in order to accurately represent anomalies with wavelengths greater than 300 km and to create smooth grid merging boundaries. The heterogeneous distribution of errors in the observations used in compiling the EMAG2v3 was explored, and is reported in the final distributed grid. This grid is delivered at both 4 km continuous altitude above WGS84, as well as at sea level for all oceanic and coastal regions.

The deep structure of the Greater Caucasus on the basis of geophysical data according to new technologies. 1. Gravimetry, magnetometry, local seismic tomography and micro seismic sounding

The data of gravity prospecting, magnetic prospecting and seismology for the study of deep structure of the earth crust of the Greater Caucasus according to software technologies have been processed and interpreted. The vertical sections depicting the distribution of the contrasts of the density and speeds in the earth crust up to the depth of 100 km under the Greater Caucasus have been constructed. Several speed and density heterogeneities of the zonal division of the Greater Caucasus, which make some corrections for the issues of orogenesis of the Greater Caucasus, have been distinguished. Comparative analysis of the obtained results and the results of the local seismic tomography and micro seismic sounding has been done.

Influence of Open Water Bodies on the Modeling of Summertime Convection over the Canadian Prairies

Abstract There are numerous water features on the Canadian landscapes that are not monitored. Specifically, there are water bodies over the prairies and Canadian shield regions of North America that are ephemeral in nature and could have a significant influence on convective storm generation and local weather patterns through turbulent exchanges of sensible and latent heat between the land and the atmosphere. In this study a series of numerical experiments is performed with Environment and Climate Change Canada’s Global Environmental Multiscale (GEM) model at 2.5-km grid spacing to examine the sensitivity of the atmospheric boundary layer and the resulting precipitation to the presence of open water bodies. Operationally, the land–water fraction in GEM is specified by means of static geophysical databases that do not change with time. Uncertainty is introduced in this study into this land–water fraction and the sensitivity of the resulting precipitation is quantified for a convective precipitation event occurring over the Canadian Prairies in the summer of 2014. The results indicate that with an increase in open water bodies, accumulated precipitation, peak precipitation amounts, and intensities decrease. Moreover, shifts are seen in times of peak for both precipitation amounts and intensities, in the order of increasing wetness. Additionally, with an increase in open water bodies, convective available potential energy decreases and convective inhibition increases, indicating suppression of forcing for convective precipitation.

Tokur gold ore–placer cluster in Amur Province: Geological–structural features and perspective of its development

The geological–structural features and gold-potential perspective of the Tokur ore–placer cluster in the Amur Province have been studied. This ore–placer cluster is a syncline composed of Paleozoic blackshale sequence, which is cut through by Late Paleozoic and Late Mesozoic intrusions. A granitoid massif is suggested at the depth on the basis of geophysical data. The cluster is distinguished by high productivity. Approximately 37 t gold from ore deposits, primarily from the Tokur deposit, and 60 t from placers have been mined out. The Tokur deposit is compared with the Natalka and Degdekan deposits from the Yana–Kolyma Province. Perspectives of the cluster area for large gold–quartz deposits and technogenic gold placers have been estimated.

Groundwater flow pattern and related environmental phenomena in complex geologic setting based on integrated model construction

Summary Groundwater flow, driven, controlled and determined by topography, geology and climate, is responsible for several natural surface manifestations and affected by anthropogenic processes. Therefore, flowing groundwater can be regarded as an environmental agent. Numerical simulation of groundwater flow could reveal the flow pattern and explain the observed features. In complex geologic framework, where the geologic–hydrogeologic knowledge is limited, the groundwater flow model could not be constructed based solely on borehole data, but geophysical information could aid the model building. The integrated model construction was presented via the case study of the Tihany Peninsula, Hungary, with the aims of understanding the background and occurrence of groundwater-related environmental phenomena, such as wetlands, surface water–groundwater interaction, slope instability, and revealing the potential effect of anthropogenic activity and climate change. The hydrogeologic model was prepared on the basis of the compiled archive geophysical database and the results of recently performed geophysical measurements complemented with geologic–hydrogeologic data. Derivation of different electrostratigraphic units, revealing fracturing and detecting tectonic elements was achieved by systematically combined electromagnetic geophysical methods. The deduced information can be used as model input for groundwater flow simulation concerning hydrostratigraphy, geometry and boundary conditions. The results of numerical modelling were interpreted on the basis of gravity-driven regional groundwater flow concept and validated by field mapping of groundwater-related phenomena. The 3D model clarified the hydraulic behaviour of the formations, revealed the subsurface hydraulic connection between groundwater and wetlands and displayed the groundwater discharge pattern, as well. The position of wetlands, their vegetation type, discharge features and induced landslides were explained as environmental imprints of groundwater. The highly vulnerable wetlands and groundwater-dependent ecosystems have to be in the focus of water management and natural conservation policy.

Ore potential trends in Finland: Indications from geochemical, geophysical and lineament data

The regional scale ‘geo-characteristics’ of Finnish metallic ore deposits are examined by using the existing large geochemical and geophysical databases of Geological Survey of Finland. For the study, lithogeochemical and geophysical grid values were interpolated at the location of 612 ore deposits. The parameters examined were major geochemical elements, gravity, airborne magnetic and electromagnetic data and radiometric U, Th and K radiation. Additionally, topographic lineament density was used to estimate variations in rock fractures and faulting. The grid values interpolated to deposit locations were further compared with threshold values representing the modal, ‘most common’ value for each grid.The comparison indicated significant and characteristic differences in parameters between interpolated grid values at ore locations and the threshold values of the grids. The significance of these variations was also statistically verified. The findings included the following:•Interpolated levels of CaO, FeO, MgO and MnO are relatively high and SiO2, K2O and K-radiation low in the majority of ore deposit locations indicating the intermediate to mafic environment of the deposit environments in regional scale. U radiation is also commonly high, referring to increased mobile elements during ore forming processes. These parameters also characterize the most common Ni_Cu deposit group (130 out of 612 deposits).•There is a very close connection between gold and enhanced MnO at the regional scale throughout Finland. CaO, FeO, MgO, and the electromagnetic quadrature (imaginary) component are also high at the locations of Au deposits.•A magnetic high is common for deposit environments containing Fe, Ti, V, and Zn.•Locations of PGM (platinum group metal) deposits are characterized by high CaO, MgO, MnO, and magnetic levels, but low gravity, thorium, and lineament density.•High gravity and U radiation are common.•Lineament density is elevated in several deposits containing Fe, U, Ni, Zn, Cu Au, V and Sn.Detailed examples are provided for selected deposit groups. Moreover, a summary diagram is presented of 27 major Finnish deposit types. It is evident, that the significant relationships between ore deposits and the analyzed variables can be used to guide future exploration work from known deposits to future ore potential target areas. In addition, combinations of selected variables can be useful in detailed targeting for mineralizations.

Evolution of the gulf of Cadiz margin and southwest Portugal contourite depositional system: Tectonic, sedimentary and paleoceanographic implications from IODP expedition 339

The contourite depositional system (CDS) along the southwestern Iberian Margin (SIM), within the Gulf of Cadiz and offshore areas of western Portugal bear the unmistakable signal of Mediterranean Outflow Water (MOW) exiting the Strait of Gibraltar. This locality records key information concerning the effects of tectonic activity on margin sedimentation, the effects of MOW dynamics on Atlantic circulation, and how these factors may have influenced global climate. Over the last four decades, numerous studies have been conducted on the late Miocene, Pliocene and Quaternary sedimentary stacking pattern of Neogene basins along the SIM for both academic and resources exploration purposes. However, understanding of the region rests primarily on basic seismic stratigraphy calibrated with limited data from only a few exploration wells. The Integrated Ocean Drilling Program (IODP) Expedition 339 recently drilled five sites in the Gulf of Cadiz and two sites on the western Iberian margin. The integration of core and borehole data with other geophysical databases leads us to propose a new stratigraphic framework. Interpretation of IODP Exp. 339 data along with that from industry sources and onshore outcrop analysis helps refine our understanding of the SIM's sedimentary evolution.We identify significant changes in sedimentation style and dominant sedimentary processes, coupled with widespread depositional hiatuses along the SIM within the Cadiz, Sanlucar, Doñana, Algarve and Alentejo basins. Following the 4.5Ma cessation of a previous phase of tectonic activity related to the Miocene–Pliocene boundary, tectonics continued to influence margin development, downslope sediment transport and CDS evolution. Sedimentary features indicate tectonic pulses of about 0.8–0.9Ma duration with a pronounced overprint of ~2–2.5Ma cycles. These more protracted cycles relate to the westward rollback of subducted lithosphere at the convergent Africa-Eurasia plate boundary as its previous NW–SE compressional regime shifted to a WNW–ESE direction. Two major compressional events affecting to the Neogene basins at 3.2–3Ma and 2–2.3Ma help constrain the three main stages of CDS evolution. The stages include: 1) the initial-drift stage (5.33–3.2Ma) with a weak MOW, 2) a transitional-drift stage (3.2–2Ma) and 3) a growth-drift stage (2Ma-present time) with enhanced MOW circulation into the Atlantic and associated contourite development due to greater bottom-current velocity. Two minor Pleistocene discontinuities at 0.7–0.9Ma and 0.3–0.6Ma record the effects of renewed tectonic activity on basin evolution, appearing most prominently in the Doñana basin. Several discontinuities bounding major and minor units appear on seismic profiles. Quaternary records offer the clearest example of this, with major units of about 0.8–0.9Ma and sub-units of 0.4–0.5Ma. Sedimentation is controlled by a combination of tectonics, sediment supply, sea-level and climate. This research identifies time scales of tectonic controls on deep-marine sedimentation, specifically over periods of 2.5–>0.4Ma. Shorter-term climatic (orbital) mechanisms control sedimentation at time scales of ≤0.4Ma. The role of bottom water circulation and associated processes in shaping the seafloor and controlling the sedimentary stacking pattern on continental margins has to be seriously reconsidered in future multidisciplinary studies. This is not only because of the common occurrence of sandy contourite deposits in deep water setting and their economic interest for hydrocarbon exploration, but principally because they archive the heartbeat of the interior Earth and therefore have important sedimentary and paleoceanographic implications.

Tectonics and evolution of the lithosphere of the eastern fragment of the Mongol-Okhotsk orogenic belt

The article describes tectonics and the deep structure of the lithosphere in the eastern fragment of the Mongol-Okhotsk orogenic belt according to results of analysis of the geological and geophysical database. With account of palinspastic reconstructions, the model is developed to show the most probable paleogeodynamics of the lithosphere in the Mongol-Okhotsk orogenic belt and its heterochronous terrains.

Structure Design of the Database in the INS/Database Matching Navigation System

Using the geophysical field data matching navigation could improve the concealment of the underwater vehicle, and it is also an important navigation technology in the future. Using the database to save the navigation data not only could overcome the drawbacks when using the files to storage the data but also integrated the different database together. The QNX Database is used to be the database management system (DBMS) of the INS/Database matching navigation system. According to the needs of the INS/Database matching navigation system and the relationship of the geophysical field data, the structure of geophysical field data database is designed and implemented. The result shows that the DBMS has well real-time performance, reliability and scalability. It meets the requirements of the DBMS.

Paleo-bathymetry of the northern North Atlantic and consequences for the opening of the Fram Strait

In the past decade, the geophysical database in the northern North Atlantic and central Arctic Ocean constantly grew. Though far from being complete, the information from new aeromagnetic and seismic data north of the Jan Mayen Fracture Zone and in the Arctic Ocean, in combination with existing compiled geological and geophysical data, is used to produce paleo-bathymetric maps for several Cenozoic time intervals. This paleo-bathymetric model provides evidence for an initial deep-water exchange through the Fram Strait starting around 17 Ma. Furthermore, the model suggests that crustal rifting prior to initial seafloor spreading might have facilitated an earlier deep-water connection. This confirms that the paleo-topography of the Yermak Plateau played an important role in allowing at least the exchange of shallow water between the northern North Atlantic and the Arctic Ocean before the opening of the deep-water Fram Strait gateway. In the south of the research area the paleo-bathymetric model indicates that the first possibility for a deep-water overflow from the Norwegian-Greenland Sea to the North Atlantic could have been between 15 and 20 Ma.

地震防災のための統合化地下構造データベースの構築

地震防災のための統合化地下構造データベースの構築

The Geophysical Database Management System in Taiwan

The Geophysical Database Management System (GDMS) is an integrated and web-based open data service which has been developed by the Central Weather Bureau (CWB), Taiwan, ROC since 2005. This service went online on August 1, 2008. The GDMS provides six types of geophysical data acquired from the Short-period Seismographic System, Broadband Seismographic System, Free-field Strong-motion Station, Strong-motion Building Array, Global Positioning System, and Groundwater Observation System. When utilizing the GDMS website, users can download seismic event data and continuous geophysical data. At present, many researchers have accessed this public platform to obtain geophysical data. Clearly, the establishment of GDMS is a significant improvement in data sorting for interested researchers.

AEM Data Quality Assurance and Control Procedures – A work in progress

Airborne electromagnetic data (AEM) are used in many and diverse applications such as mineral and energy exploration, groundwater investigations, natural hazard assessment, agriculture, city planning and defence. Unfortunately, many users do not have access to a simple workflow for assessing the quality of the data that they are using. This poster outlines the main quality assurance and quality control (QA-QC) procedures used by Geoscience Australia (GA) for our 2008-11 AEM surveys. Geoscience Australia is embarking on a project to upgrade the National Airborne Geophysical Database to better manage the data from major AEM surveys. This will better preserve the data and associated documentation to allow users to access and take advantage of the data well into the future. The quality of historical data included in this endeavour will unfortunately be variable and dependent on the QA-QC standards of the time. Awareness and implementation of standardised QA-QC techniques ensure future generations of AEM data captured in the National Airborne Geophysical Database will be to a higher standard.

The impact of Mars geological evolution in high energy ionizing radiation environment through time

Radiation levels expected at the surface of Mars are known to have an impact on life form as well as biological and organic materials. Therefore the ionizing radiation must be studied in order to evaluate the potential organic preservation on Mars.MarsREC (Keating et al., 2005) and dMEREM (Gonçalves et al., 2009) are ionizing radiation environment characterization models based on GEANT4 (Agostinelli et al., 2003) Monte Carlo applications developed for the European Space Agency. Enabling the interface with geophysical databases, these models allow the evaluation of Martian radiation environment as a function of climatological and geological variables.This work defines critical geophysical parameters associated with geological evolution and assesses their impact in terms of radiation environment.Results show that the erosion of the Martian atmosphere and the regolith, due to the LHB era, led to an important increase of the radiation environment, consequently radiation hazard, and led to the degradation of habitability conditions at the surface of Mars.

Influence of fluid systems of the consolidated crust on degassing of the earth and oil formation

Fluid systems in the consolidated continental crust associated with large permeable zones have been distinguished on the basis of geophysical data. These zones serve as migration pathways for fluids uplifting from the mantle. The conditions of interaction of such fluids with large horizontal and subvertical fluid systems during degassing are considered. Horizontal systems, fixed at geophysical profiles as waveguides, contain significant amounts of high-temperature fluids, which interact there with enclosing rocks and fluids uplifting during degassing with the formation of oil- and ore-bearing solutions. The experiments on the interaction of water and solutions with rocks under increased temperatures carried out in the second half of 1960s gave an idea about the character of similar reactions. It has been revealed that significant amounts of organic matters pass into solutions, and bitumen is generated at 150–250°C. Similar reactions promote formation of new oil fields.

Results of comprehensive studies of the underground hydrosphere within the western shoulder of the Baikal rift (as exemplified by the Bayandai - Krestovsky Cape site)

Results of comprehensive studies of the underground hydrosphere within the western shoulder of the Baikal rift (as exemplified by the Bayandai - Krestovsky Cape site)

Chapter 42 Greenland petroleum exploration: history, breakthroughs in understanding and future challenges

Abstract In recent years there has been a growing interest from the industry for exploration in the Arctic and other high-latitude areas, including possible future petroleum provinces in Greenland. Exploration focus in Greenland has mainly been on central west Greenland with several licensing rounds and, as a promising result, the highest number of licences ever seen in Greenland. Activities in the coming years are likely to be directed more towards Baffin Bay and to the NE Greenland shelf. Both of these regions offer very promising exploration targets but also major technical challenges due to many months of ice coverage every year. Preparations for new exploration, data acquisition and geological and geophysical work are in progress in these two regions. Both of the regions benefit from excellent outcrops in the neighbouring onshore areas and a rapidly increasing geophysical database offshore. The history behind data acquisition and the most important results and models for exploration in some of the possible future petroleum provinces are described with particular focus on positive indications for structures and petroleum systems together with uncertainties in interpretation and the most critical risks for exploration. Supplementary material: Supplementary Table 1 is available at http://www.geolsoc.org.uk/SUP18477 .

Thermodynamic Modeling of the Earth's Interior

The validity and usefulness of thermodynamic models commonly used to model the physical and chemical properties of Earth's interior at high to ultrahigh pressures and their associated geophysical databases are discussed. All calorimetric data used in these models must have the quality of fitting to experimental phase diagrams derived from work not only at high temperatures and pressures but also under ambient conditions. The density and temperature profiles calculated for Earth's mantle and core and the phase diagram of iron calculated under core conditions illustrate how thermodynamic modeling helps us understand the physics of Earth's deep interior.

Extensional tectonics in the Campania Volcanic Zone (eastern Tyrrhenian Sea, Italy): new insights into the relationship between faulting and ignimbrite eruptions

The Campania Volcanic Zone (CVZ), located on the eastern margin of the Tyrrhenian Sea, is a region characterized by active tectonics and large ignimbrite eruptions starting from 290 ka. A reconstruction of the three-dimensional architecture of the ignimbrite deposits and faults of the CVZ (Campania Plain and Bay of Naples) was made by means of the interpretation of an integrated geological geophysical database. This reconstruction, based on several geological sections combined into two fence diagrams and isopach maps showing the distribution of ignimbrites, reveals: (i) a regional fault pattern characterized by NE-SW, NNE-SSW, NW-SE and E-W structures active over the last 290 ka during ignimbrite eruptions; (ii) a location of the ignimbrite vents over the whole CVZ in correspondence to NE-SW and NW-SE faults; (iii) volcano-tectonic subsidence along normal separation faults that produced asymmetric basins. Furthermore, we have established the tectonic evolution of the CVZ from the emplacement of the ignimbrite deposits, and infer the presence of a WNW-ESE trending extension associated with NNE-SSW normal faults, E-W transfer faults and the reactivation, as transtensional faults, of the NE-SW and the NW-SE structures. The results of this study conflict with the occurrence of a caldera at Campi Flegrei and Naples Bay.

Automated integration of partially colocated models: Subsurface zonation using a modified fuzzy c -means cluster analysis algorithm

Partitioning cluster analyses are powerful tools for rapidly and objectively exploring and characterizing disparate geophysical databases with unknown interrelations between individual data sets or models. Despite its high potential to objectively extract the dominant structural information from suites of disparate geophysical data sets or models, cluster-analysis techniques are underused when analyzing geophysical data or models. This is due to the following limitations regarding the applicability of standard partitioning cluster algorithms to geophysical databases: The considered survey or model area must be fully covered by all data sets; cluster algorithms classify data in a multidimensional parameter space while ignoring spatial information present in the databases and are therefore sensitive to high-frequency spatial noise (outliers); and standard cluster algorithms such asfuzzy [Formula: see text]-means (FCM) or crisp [Formula: see text]-means classify data in an unsupervised manner, potentially ignoring expert knowledge additionally available to the experienced human interpreter. We address all of these issues by considering recent modifications to the standard FCM cluster algorithm to tolerate incomplete databases, i.e., survey or model areas not covered by all available data sets, and to consider spatial information present in the database. We have evaluated the regularized missing-value FCM cluster algorithm in a synthetic study and applied it to a database comprising partially colocated crosshole tomographic P- and S-wave-velocity models. Additionally, we were able to demonstrate how further expert knowledge can be incorporated in the cluster analysis to obtain a multiparameter geophysical model to objectively outline the dominant subsurface units, explaining all available geoscientific information.