Near surface Geophysics Research Papers (original) (raw)

4th European Conference on Permafrost (EUCOP4), Évora, Portugal, 18-21 June 2014

This research deals with the detection of possible surface soil pollution by radon emissions for an area located inside the university of Baghdad campus at AL-Jadiriyah / Baghdad. The area is about 5625 m 2 and located near the College of... more

This research deals with the detection of possible surface soil pollution by radon emissions for an area located inside the university of Baghdad campus at AL-Jadiriyah / Baghdad. The area is about 5625 m 2 and located near the College of Science for Women. The area used as construction rubbles dump yard in the past, while recently it is covered with Silty-Clayey soil furnished with grass and used as a playground. A surface survey performed on October 2018 by gridding the area into 36 stations where surface radiometric pollution readings recorded and soil samples collected by using an auger for the top 30 Cm which represents the root zone of the area. Soil samples tested in the laboratory by using can technique with CR-39 type track detectors, while surface readings performed by using a portable Geiger counter device. Soil surface readings and laboratory analysis results were processed by computer in order to draw contour maps which showed the variation of radon emission anomalies across the area. The aim behind this processing and interpretation is to provide an evaluation for the health environmental impact related to the radioactivity of the top soil and the area surface. The results of this study showed that radon emissions were below the standard limits and this makes it possible to invest the area for future human housing and other activities.

This project follows a rationale of inquiry based geophysics for implementing new prospective methods based on developing trends in research. Upland sites, especially hillforts, are the hallmark of the Iron Age, but their remote locations... more

This project follows a rationale of inquiry based geophysics for implementing new prospective methods based on developing trends in research. Upland sites, especially hillforts, are the hallmark of the Iron Age, but their remote locations and difficult conditions have curtailed extensive excavation in the recent past. By understanding potential targets and their value to research agendas archaeogeophysics has the potential to rapidly develop the understanding of prehistoric enclosures and habitation patterns. Electromagnetic induction (EMI) devices are ideal for survey in upland environments as they do not rely on probes or contact with soil. This study compares the outputs of surveys carried out with an EMI device, the CMD Mini-Explorer, against a dual fluxgate gradiometer. Topsoil susceptibility measured with a coincidental loop is also compared.

In contrast to the use of marine seismic reflection techniques for reservoir-scale applications, where seismic inversion for quantitative sediment analysis is common, shallow-water, very-high-resolution seismic reflection data are seldom... more

In contrast to the use of marine seismic reflection techniques for reservoir-scale applications, where seismic inversion for quantitative sediment analysis is common, shallow-water, very-high-resolution seismic reflection data are seldom used for more than qualitative reflection interpretation. Here, a quantitative analysis of very-high-resolution marine seismic reflection profiles from a shallow- water (<50 m water depth) fjord in northern Norway is presented. Acquired using Sparker, Boomer, and Chirp sources, the failure plane of multiple local landslides correlates with a composite reflection that reverses polarity to the south. Using a genetic algorithm, a 1D post-stack acoustic impedance inversion of all three profiles is performed, calibrating against multi-sensor core logger (MSCL) data from cores. Using empirical relationships the resulting impedance profiles are related to remote sediment properties, including: P-wave velocity; density; mean grain size; and porosity. The composite reflector is consistently identified by all three data sources as a finer-grained (by one Phi), lower density (c. 0.2 g/cm3 less than background) thin bed, with an anomalous low velocity zone (at least 100 m/s lower than background) associated with the polarity reversal to the south. Such a velocity contrast is consistent with an accumulation of shallow free gas trapped within the finer- grain, less permeable layer. This study represents the first application of acoustic impedance inversion to very-high-resolution seismic reflection data and demonstrates the potential for directly relating seismic reflection data with sediment properties using a variety of commonly used shallow seismic profiling sources.

2D seismic refraction data, from seven traverse lines, were used to investigate subsurface geology in the Appollonian Formation of the onshore Tano Basin of Ghana. Tano Basin is one of the four basins of Ghana and the most important one... more

2D seismic refraction data, from seven traverse lines, were used to investigate subsurface geology in the Appollonian Formation of the onshore Tano Basin of Ghana. Tano Basin is one of the four basins of Ghana and the most important one when it comes to oil potential of Ghana. The survey covered approximately a total area of about 113,000 m 2. With the exception of one traverse line which had the length of 60 m, each of the remaining traverse lines had a length of 120m. The results from the data analysis indicated that, the surveyed area is underlain by three geological units although results from two traverse lines revealed two geological units. The P-wave velocity of the first layer ranges between 335.00-468.00 m/s and the average velocity of 391.57 m/s. It has a thickness range of 5.0-27.5 m with an average thickness of 16.25 m. The layer is interpreted as a weathered layer and consist of soil and dry loose sand which might be formed as beach deposit. The second layer has P-wave velocity range of 590.00-1133.00 m/s and the average velocity of 881.71 m/s. The layer thickness ranges between 14.5-31.0 m and the average of 25.80 m. The layer may consist of unconsolidated water-saturated sand and clay. The last layer detected by this survey has P-wave velocity range of 1068.00-2724.00 m/s and the average of 2074.20 m/s. The layer is interpreted as the bedrock underlining the surveyed area. The layer may consist of gravel, sandstone and limestone.

Small, low cost Autonomous underwater vehicles (AUVs) provide ideal platforms for shallow water survey, as they are capable of unmanned navigation and can be programmed to acquire data at constant depth, or constant altitude above the... more

Small, low cost Autonomous underwater vehicles (AUVs) provide ideal platforms for shallow water survey, as they are capable of unmanned navigation and can be programmed to acquire data at constant depth, or constant altitude above the seabed. AUVs can be deployed under most sea states and are unaffected by vessel motions that often degrade sonar and magnetometer data quality. The integration of sonar and magnetometer sensors on AUV’s is challenging, however, due to limited payload and strong magnetic fields produced by the vehicle motor.
In this study, a Marine Magnetics Explorer Overhauser magnetometer was mated to a portable AUV (OceanServer Iver2) creating the first practical AUV- deployed magnetic survey system. To eliminate magnetic interference from the AUV, the magnetometer was tethered to the AUV with a 5 m tow cable, as determined by static and dynamic instrument testing. The results of the magnetic tests are presented, along with field data from a shallow water test area in Lake Ontario near Toronto, Canada. AUV-acquired magnetic survey data were compared directly with a conventional boat-towed magnetic survey of the same area. The AUV magnetic data were of superior quality despite being collected in rough weather conditions that would have made conventional survey impossible. The resulting high-resolution total magnetic intensity and analytic signal maps clearly identify several buried and surface ferrometallic targets that were verified in 500-kHz side- scan sonar imaging and visual inspection by divers.

The electromagnetic profiling and Vertical Electrical Sounding (VES) data were acquired from some communities in the Twifo-Hemang Lower Denkyira District of the Central region of Ghana, in order to determine zones of high groundwater... more

The electromagnetic profiling and Vertical Electrical Sounding (VES) data were acquired from some communities in the Twifo-Hemang Lower Denkyira District of the Central region of Ghana, in order to determine zones of high groundwater potentials and to recommend suitable sites to drill boreholes for community water supply. The research reported here covered three communities namely; Esukese Ekyire, Kwanyarko. First the electromagnetic measurements were carried out, qualitative interpretations of the data were carried out and weathered rock zones were identified. Then the VES measurements using Schlumberger array were conducted at points on the electromagnetic traverse that displayed weathered zones. ZONDIP1D software was used in creating 1D sounding curve models of geological subsurface structures beneath the sounding points. Results of the modelling suggest that the communities are underlain by three to four geological layers. Interpretations of the 1D inversion of the VES data provide the resistivities and thicknesses of subsurface layers. On the basis of resistivity values and thicknesses of the layers in the 1D models, sites were recommended to drill boreholes for community water supply.

Abstract The renovation of a proposed railway bridge in Akere, North Central Nigeria was investigated using integrated Geotechnical (SPT) and Geophysical methods (2-D and 3-D resistivity imaging using multi-electrode system and extracted... more

Abstract
The renovation of a proposed railway bridge in Akere, North Central Nigeria was investigated using integrated Geotechnical (SPT) and Geophysical methods (2-D and 3-D resistivity imaging using multi-electrode system and extracted vertical electrical sounding techniques). Frequent flooding from the Niger River on overflowing it’s banks have been washing away the railway section along this section and several engineering foundation precaution taken have proved abortive. Eight traverses of 2-D lines, one 3-D section and sixty four extracted VES data were acquired and interpreted. Inter electrode spacing of 1m and inter traverse spacing of 3m were adopted for better near surface resolution. The subsurface layers were characterized by top soil, clay, clayey sand/sandy clay, weathered/intensely fractured rock, sand and fresh basement. The 8 borehole data earlier acquired were integrated with the 2-D and 3-D Resistivity tomography results. A perfect correlation was obtained for the two techniques. However all the boreholes terminated at shallow depth (5 – 11m), and did not provide information beyond this depth while the Resistivity tomography penetrated to a depth of about 15 – 20m and revealed the presence of structurally weak materials (Clay/Fractured basement) inimical to the foundation of the rail line along the traverses. The 2-D and 3-D resistivity tomography shows that the first aquifer is underlain by clay layer separating the upper aquifer unit from the lower aquifer unit, this was further corroborated by the VES results. The presence of low resistivity subsurface materials compose of clay/clayey sand within a depth range of 10 –17m may accelerate failure of piles along the Railway line. This layer is inimical to the proposed rail line. The depth to the competent soil material along where the failed (10 to 20m) piles were installed varies compared to adjacent regions (3 – 6m). It was therefore recommended that necessary precaution in foundation design to competent layer or to exploit the adjacent shallow competent region be considered. Pile foundation to varying depths within the competent region is recommended and should be socketed and anchored within the basement rock which occur at varying depths within the investigated area. The integration of geotechnics and invaluable multi-dimensional variation of subsurface distribution provided in the geophysical investigation have provided an insightful and lasting solution to the foundation problems encountered.

Electromagnetic (EM) profi ling and Vertical Electrical Sounding (VES) studies were carried out for groundwater exploration in the Twifo-Hemang Lower Denkyira Districts of Ghana. These two geophysical methods were used for exploring the... more

Electromagnetic (EM) profi ling and Vertical Electrical Sounding (VES) studies were carried out for groundwater exploration in the Twifo-Hemang Lower Denkyira Districts of Ghana. These two geophysical methods were used for exploring the groundwater potentials beneath Achiase Community, Mbaa Mpe Hia Community and Moseaso Community. This paper seeks to encourage the use of inversion for interpreting electromagnetic data rather than the usual qualitative interpretation method using line graphs and also the use of apparent resistivity maps as 2D pseudo resistivity maps to support interpretations of the 1D inversion results (in cases where the available budget could not permit 2D and or 3D inversion). These would help in enhancement of obtained results, reduce ambiguity and help decision making. The EM results revealed that; the three communities are underlain by two layers with the fi rst layer having the thickness range between 2 to 10 m and the second layer is a half space. The results from VES studies indicate that; Achiase Community and Mbaa Mpe Hia No. 2 community are underlain by three geoelectrical layers and Moseaso Community is underlain by four geoelectrical layers. On the basis of this study the Moseaso Community is ranked highest in terms of groundwater potential followed by the Achiase community and fi nally the Mbaa Mpe Hia No.2 Community. Several sites were recommended for drilling boreholes for water supply in these communities.

Geophysical methods have been used with increasing frequency in archaeology since 1946; aerial photography has been used since 1919. The geophysical methods that are most commonly used at present are electrical resistivity, magnetics, and... more

Geophysical methods have been used with increasing frequency in archaeology since 1946; aerial photography has been used since 1919. The geophysical methods that are most commonly used at present are electrical resistivity, magnetics, and ground-probing radar. Magnetic detectors, particularly when used in
a gradient mode or with a continuously recording base station, are used at almost all sites where any geophysical methods are used. Portable, noncontacting electromagnetic soil-conductivity systems are also being increasingly used because of their very high rate of data acquisition. Less commonly used methods
include self-potential (sometimes called spontaneous potential), microgravity, radiometric, thermal infrared imagery, and sonic or seismic techniques. Recent developments in image processing and graphic representation have contributed substantially to the archaeologist’s ability to do “rescue archaeology,” that is, to carry out high-speed, nondestructive reconnaissance surveys for ancient human cultural evidence in advance of modern industrial development.

Kajian arkeologi di Lembah Mansuli, Lahad Datu, Sabah Ielah menemukan dua tapak Paleolitik, iaitu Gua Samang Buat dan tapak terbuka Mansuli. Isu utama di Gua Samang Buat ialah berapakah kedalaman sedimen di dalamgua ini selepas... more

Kajian arkeologi di Lembah Mansuli, Lahad Datu, Sabah Ielah menemukan
dua tapak Paleolitik, iaitu Gua Samang Buat dan tapak terbuka Mansuli. Isu utama
di Gua Samang Buat ialah berapakah kedalaman sedimen di dalamgua ini selepas
ekskavasi empat meter masih belum menemui lantai gua. Manakala isu utama di
tapak terbuka Mansuli ialah interpretasi paleoalamnya yang dikatakan bersekitaran
tasik kuno. Maka, kaedah geoftzik telah digunakan untuk cuba menjawab isu ini.
Penggunaan kaedah geofizik di Lembah Mansuli telah berjaya membantu
mengenalpasti ketebalan sedimen di Gua Samang Buat dan membantu membina
paleoalam untuk Lembah Mammli. Ketebalan sedimen gua di Gua Samang Buat
yang boleh di' ekskavasi ialah 12 m di Gua 1 dan 5 m di Gua 2. Data ini
mencadangkan secara relatifberkemungkinan kita boleh menemui lapisan berusia
138,000 tahun dahulu di Gua Samang Buat berdq~rkan usia 46,000 untuk
kedalaman 4 m. Kajian gwifizik di Lembah Mansuli pula mendedahkan wujud
tasik kuno dan sa/iran sungai kuno di Lembah Mansuli. Malah daripada survei
tersebut, ianya juga mendedahkan kemungkinan wujud dua teres tasik kuno. Modelanomali graviti dan magnet juga turut menghasilkan hentuk tasik.

This work presents an analysis of the physical principles of the electromagnetic methods in Geophysics, based on the behavior of the electromagnetic field in matter. The mathematical computation is done for the solution of a model which... more

This work presents an analysis of the physical principles of the electromagnetic methods in Geophysics, based on the behavior of the electromagnetic field in matter. The mathematical computation is done for the solution of a model which approximates the electromagnetic behavior of the subsurface, making a system of parallel, homogeneous and isotropic layers. The direct problem in geoelectrics is solved, creating an algorithm for this purpose and comparing its results with those of specialized interpretation software: IPI2win.
As part of the project ‘Proyecto Borde Norte de Bogotá’, it is participated in the field work, process, and geophysical interpretation, providing results that contribute to support the declaration of the Northern Regional Forest Reserve (RFRN in Spanish).

Iraq is one of the countries that contain many important archaeological sites and manifestations of varied cultural heritage belonging to ancient civilizations. Several archaeological sites and cultural heritage are disappeared as a... more

Iraq is one of the countries that contain many important archaeological sites and manifestations of varied cultural heritage belonging to ancient civilizations. Several archaeological sites and cultural heritage are disappeared as a result of neglect, climate influences and manufactured interventions. In this study, two different radar data were used to image the subsurface with different scales, namely synthetic aperture radar (SAR) image and ground penetrating radar (GPR) data. SAR image was used to extract information regarding potential archaeological remains in Ukhaidir site, southwest of Karbala city. ALOS PALSAR (L-band) image was used to identify and detect the ground anomalies due to the presence of near-surface archaeological structures. Advanced image processing and classification were applied depending on the intensity bands (HH and HV) including texture analysis by application of the Gray Level Co-occurrence Matrices (GLCM) and Principal Component Analysis (PCA) to nominate potential archaeological sites. The results led to identifying 15 sites, eight of them were excluded because they were not covered and clearly visible in the recent high-resolution image and in the field observation, which appears as hills containing scattered stone remains and brick walls. Seven sites (namely P1 to P7) nominated as potential archaeological remains, which were completely covered with loose sand, and its areas are ranging between 873-3774 km2 approximately. Potentially, they might be represented remains of structures for dwelling house or rooms were used by communities living near the fortress.
2D GPR survey were conducted at two sites (sites A and B) near the fortress using a 250 MHz shielded antenna to verify the results of ALOS imagery and historical information, and to characterize and depict the potential subsurface of the buried objects. Site A was in front of the fortress by a few meters included two parallel profiles with a distance of five meters separates between the profiles and 100 m length of each profile. While site B (Site P2) located about 155 m northeast, the fortress included nine parallel GPR profiles with 42.5 m length of each profile and one-meter distance between the profiles, which already covered an area of 8 x 42.5 m (340 m2).
The results of 2D GPR profiles in site A showed four anomalies in the shallow part caused by energy attenuation. Three of them are probably associated with demolished walls of archaeological structures. While the greater anomalies probably associated with Karez (water canal). The results of 2D GPR profiles in site B revealed a number of anomalies interpreted as demolished walls appeared on shallow depths begin approximately 0.15 to 0.3 m below surface, continue down to various depths, and have a width ranging from 0.5-5 m. One of the important anomalies that have been distinguished is the fence (external wall) at a depth of about 0.2 m and around 7 m width.
GPR attribute analysis were used including the instantaneous phase, RMS amplitude, and sweetness attributes to improve the interpretation and achieve the best results. The results led to the identification of a number of anomalies; six were interpreted to be ancient walls, while the others were associated with Karez and fence. RMS amplitude and sweetness attributes successfully determined the boundaries and the horizontal continuity of the ancient walls, but RMS amplitude was more accurate. While the instantaneous phase highlighted the high contrast features of the buried structures and failed to specify the targets that have an angle equal or close to the soil phase angle. The anomalies in the site A appeared with high amplitudes than the anomalies of site B. This is due to the expected archaeological structures in the site A probably constructed from stone, while the structures of site B was built with clay brick.

The Lake Jackson Mounds site, located near Tallahassee, Florida, has long been considered to be a frontier Mississippian center. This assertion is primarily based on elaborate burial goods recovered during salvage excavations. Ground... more

The Lake Jackson Mounds site, located near Tallahassee, Florida, has long been considered to be a frontier Mississippian center. This assertion is primarily based on elaborate burial goods recovered during salvage excavations. Ground penetrating radar (GPR) on the two largest intact mounds at Lake Jackson revealed new information about their morphology and construction histories. These findings demonstrate that mound-building practices at the site were distinct from earlier, local Woodland mound-building traditions, and more similar to those of other Mississippian centers, such as Etowah and Moundville. Lake Jackson revitalized mound building in the Tallahassee area under the influence of external connections with groups in the Mississippian interaction network. These findings show how mound building was an integral practice for expressing and expanding Mississippian ideologies and rituals. This work also shows the utility of GPR in exploring mounds' morphologies and construction histories.

Integrated geotechnical and geophysical investigation of a wetland dumpsite in Epe, Lagos State, Nigeria, was carried out with a view to determining the hydraulic properties of the underlying formation for possible leachate transmission... more

Integrated geotechnical and geophysical investigation of a wetland dumpsite in Epe, Lagos State, Nigeria, was carried out with a view to determining the hydraulic properties of the underlying formation for possible leachate transmission and subsequent subsoil pollution. Eleven boreholes were drilled, lithologically logged, sampled and analysed for hydraulic/hydrogeological parameters. Geophysical investigation involved 1-D Vertical Electrical Soundings (VES) (8 Nos.) and 2-D Dipole-Dipole profiling along five traverses. The survey area is underlain by fine-medium grained sands with coefficient of uniformity values of < 6. The fresh water saturated sandy formation is characterized by relatively high layer resistivity values (5681-9889 Ωm). The mean bulk-3-4-4 density is 1.89±0.162 g/cm ; porosity: 37.84±8.42%; and permeability: 3.0 x 10 ± 1.1 x 10 cm/sec. The 2D images identify leachate impacted zone beneath the waste dump site and its periphery characterized by relatively low resistivity values (4 to 165 Ωm). The study concluded that the sandy nature of the subsoil and its moderate permeability aided subsoil and groundwater pollution by leachate to depths in excess of 15 m.

Salt water intrusions of marine origin are a major cause of contamination for coastal fresh water aquifers. They are generated mainly by the uncontrolled exploitation of fresh water in pumping stations from coastal areas. In Romania, such... more

Salt water intrusions of marine origin are a major cause of contamination for coastal fresh water aquifers. They are generated mainly by the uncontrolled exploitation of fresh water in pumping stations from coastal areas. In Romania, such marine intrusions have occurred in the southern part of Black Sea's coastline, in the area of Vama Veche and Costineşti resorts, contaminating the main aquifers which are hosted within Sarmatian (late Middle Miocene) lumachelic and oolitic limestones. Fresh water exploitation management requires the identification, mapping and monitoring of marine intrusions. These are achievable by means of an adequate application of geoelectrical methods, because sea water intrusions lead to major variations of the aquifers resistivity. Apparent resistivity surveys such as electrical profiling and vertical electrical sounding (VES) are able to delineate the areal extent of these intrusions and to identify the approximate depth of the fresh water/salt water interface. Assuming the subsurface geology consists of horizontal and homogeneous layers, the VES apparent resistivity data can be interpreted in terms of layer thicknesses and true resistivities, i.e. a one-dimensional (1-D) geoelectrical model with a stepwise variation of true resistivity with depth. The optimal model is obtained by repeated forward modeling trials or through the inversion of measured apparent resistivities.
This paper presents an algorithm and a set of software applications for the forward modeling of VES apparent resistivity curves, by using digital linear filtering. The codes were elaborated in MATLAB programming environment and allow the calculation of the theoretical VES response for horizontally-layered geological media with virtually unlimited number of layers, including layers with a quasi-continuous resistivity variation. The latter option can be used to simulate particular hydrogeological situations regarding the sea water intrusions in fresh water aquifers, which often show a mixing/transition zone of variable salinity and resistivity. The interpretation of VES curves recorded in Vama Veche area by using the elaborated software indicates that the sea water intrusion occurs at more than 50 m depth. This agrees with water wells tests which confirm the presence of salt water at 40–60 m depth in that area.

The excavated architecture of the exceptional prehistoric site of Akrotiri on the Greek island of Thera/Santorini is endangered by gradual decay, damage due to accidents, and seismic shocks, being located on an active volcano in an... more

The excavated architecture of the exceptional prehistoric site of Akrotiri on the Greek island of Thera/Santorini is endangered by gradual decay, damage due to accidents, and seismic shocks, being located on an active volcano in an earthquake-prone area. Therefore, in 2013 and 2014 a digital documentation project has been conducted with support of the National Geographic Society in order to generate a detailed digital model of Akrotiri's architecture using terrestrial laser scanning and image-based modeling. Additionally, non-invasive geophysical prospection has been tested in order to investigate its potential to explore and map yet buried archaeological remains. This article describes the project and the generated results.

Aska hamlet in Hagebyhöga parish, Östergötland (Sweden), is famous among Viking scholars for a rich female burial under a low cairn that was excavated in 1920. The main visible archaeological feature of the site is an enormous barrow, but... more

Aska hamlet in Hagebyhöga parish, Östergötland (Sweden), is famous among Viking scholars for a rich female burial under a low cairn that was excavated in 1920. The main visible archaeological feature of the site is an enormous barrow, but its contents have not been excavated. As the barrow is oval and has an extensive flat top, it has been hypothesized previously that rather than a grave superstructure, this might be an uncommonly large raised foundation for a long house. We occasionally see this type of feature at elite manorial sites from the period ad 400–1100. We have tested this idea at Aska with ground-penetrating radar, securing the clear and detailed floor plan of a post-supported hall building almost 50 m long. Its closest known architectural parallel, also sitting on a similar platform, has been excavated at Old Uppsala, the late first millennium ad political and ceremonial centre of the ancient Swedes. At Aska, it appears that we have found another such real-world correlate of the Beowulf poem's royal mead-hall Heorot, but in this case located in a smaller and less powerful polity. This all suggests a petty royal status for the owners of the Aska hall, who enjoyed connections with Scandinavia's top political elite.

— Recently, the shock hazards that always come along contaminated groundwater in Laka area of Ogbomoso, south western Nigeria which contain some elements in excess quantity more than the Nigeria standard for drinking water quality 556... more

— Recently, the shock hazards that always come along contaminated groundwater in Laka area of Ogbomoso, south western Nigeria which contain some elements in excess quantity more than the Nigeria standard for drinking water quality 556 (207) recommendation for groundwater potability has become a major concern. With the aim of providing valuable information on hydrogeologic system of the aquifers, subsurface lithology, and delineating groundwater contamination, Thirty three (33) vertical electrical sounding (VES) was carried out utilizing surface Schlumberger electrode arrays and electrode spacing of 50m coupled with hydrogeochemical analysis of the surrounding hand dug wells for Cl-, Ca 2+ , Mg 2+ , Fe 3+ , No3-, calcium, hardness, total hardness e.t.c. The DC resistivity survey revealed significant variation in the subsurface resistivity. Also, VES resistivity curves showed a dominant trend of low resistivity (high conductivity) at shallow depth of ≤15m and later increases with depth. In general the presences of three-four layers were delineated viz.: sandy, sand/gravel topsoil, clay, weathered layer and the fresh bedrock. The thickness and resistivity values range respectively from 0.42 to 2.5m and 13.51 to 150.9Ωm for the top soil, 1.1 to 12.5m and 11.7 to 300.1Ωm for the weathered/clay layer. These anomalous low resistivities indicate area with contaminated groundwater. The result of the hydrochemical analysis also agreed with the presence of contamination.

wSouthern Kulon Progo, covering Temon, Wates, Panjatan, Galur, and Lendah District are earthquake prone areas. To minimize the disaster impact, design of the building should pay attention to the dynamic and local soil conditions. This... more

wSouthern Kulon Progo, covering Temon, Wates, Panjatan, Galur, and Lendah District are earthquake prone areas. To minimize the disaster impact, design of the building should pay attention to the dynamic and local soil conditions. This study aimed to obtain 3-D shear wave velocity (Vs) model in Southern Kulon Progo using HVSR inversion. Microtremor data at 25 point were analyzed using the HVSR method. The result of HVSR analysis is then carried out by inversion with the forward modeling principle to obtain Vs model of each measurement point, which will be used to create 3-D shear wave velocity (Vs). The study results showed that Vs values vary from 80 - 1500 m/s. Areas with lower Vs and dominant thick were in Wates and Panjatan. The thickness of the layer with low Vs is increasingly thinning towards the east and northwest.

Abstrak-Kelongsoran sering terjadi pada tanah yang memiliki topografi curam. Salah satunya adalah yang terjadi di Desa Jombok, Kecamatan Ngantang, Kabupaten Malang, Jawa Timur. Pada areal seluas satu hektar dijumpai penurunan permukaan... more

Abstrak-Kelongsoran sering terjadi pada tanah yang memiliki topografi curam. Salah satunya adalah yang terjadi di Desa Jombok, Kecamatan Ngantang, Kabupaten Malang, Jawa Timur. Pada areal seluas satu hektar dijumpai penurunan permukaan tanah (longsor). Daerah longsoran ini diteliti dengan menggunakan salah satu metoda Geofisika, yaitu Very Low Frequency-Electromagnetic (VLF-EM). Data lapangan yang didapatkan dari hasil pengukuran metode VLF-EM biasanya tercampur dengan noise dan outlier. Pada penelitian ini digunakan filter NA-MEMD untuk menghilangkan noise dan outlier. Digunakan Filter Karous-Hjelt untuk menganalisa data secara kualitatif. Sedangkan analisa secara kuantitatif diperoleh dengan melakukan pemodelan inversi menggunakan INV2DVLF. Hasil analisis VLF-EM dengan menggunakan filter NA-MEMD mampu mereduksi noise dan outlier dari data pengukuran. Sedangkan hasil inversi 2D menunjukkan bahwa terdapat zona anomali yang menunjukkan zona lemah atau rawan longsor di area penelitian.
Abstract-Landslide often occurs in a steep topography ground. One of them is happened in the Jombok village, Ngantang, Malang, East Java. Land subsidence (landslides) often occur in this area. The landslide area investigated using one of the Geophysics methods, the Very Low Frequency-Electromagnetic (VLF-EM). The field datas obtained from measurement results of VLF-EM method are usually mixed with noise and outliers. In this research, NA-MEMD filter.is used to eliminate the noise and outliers. Karous-Hjelt (K-Hjelt) filter is udes to qualitative analyze of the data. While quantitative analysis is obtained by performing inversion modeling using INV2DVLF. VLF-EM analysis results using the NA-MEMD filter is able to reduce the noise and outliers of measurement data. While the 2D inversion results indicate that there is an anomalous zone which indicates weak or landslide-prone zones in the study area.

Using geophysical methods for the geomorphological characterization of subsurface features has numerous advantages over traditional exploration methods, because of their noninvasive and rapid nature. In this study, we compared the results... more

Using geophysical methods for the geomorphological characterization of subsurface features has numerous advantages over traditional exploration methods, because of their noninvasive and rapid nature. In this study, we compared the results of four geophysical methods with each other. We also discuss their possibilities and limitations in a geomorphological investigation. Electrical resistivity tomography (ERT), refraction seismic (RS), ground penetrating radar (GPR), and multichannel analysis of surface waves (MASW) methods were applied at an abandoned meander in northern Saxony to map a predefined structure. By combining these methods, we were able to characterize and delineate subsurface features of the abandoned meander, including a point bar, a channel, and a cutbank. Core samples obtained from sonic drilling were used to validate the findings of both seismic methods. However, we found that electrical resistivity tomography and ground penetrating radar lacked penetration depth and could only be used to resolve shallower subsurface layers. The ERT, GPR, RS, and MASW can be used to gather images of subsurface structures. The MASW in particular provides supplementary information about the channel's internal structure (with respect to lateral and vertical resolution). Besides fluvial–morphological features, we also detected inverse velocity structures within the channel. This allowed us to characterize the abandoned meander using information about its layer distribution and material composition. However, we were only able to characterize and delineate the subsurface features of the abandoned meander by combining all of the aforementioned methods.

Barrier islands and spits are geological young, highly dynamic and represent a complex coastal system that includes a number of different but closely related sedimentary depositional environments. In this study ground-penetrating radar... more

Barrier islands and spits are geological young, highly dynamic and represent a complex coastal system that includes a number of different but closely related sedimentary depositional environments. In this study ground-penetrating radar data of different antenna frequencies and sedimentological data were combined to reveal the sedimentary structure and architecture of the southern barrier island spit of Sylt and to set up a barrier island stratigraphy. Based on these data, two sedimentological models have been generated for Southern Sylt which describes the inter-action between extreme
events, coastal processes and sedimentary development and contains the major episodes of barrier island evolution. The first model is concerned with the spit add-on zone where the barrier spit is attached to the central island moraine core and shows a landward migration through barrier rollover affected by an interplay of barrier retreat and washover flooding associated with accumulation of sediment in a backbarrier environment as a result of several storm surges. The spit add-on zone reveals a transgressive coarsening upward sequence starting with sandy mud flat deposits at the bottom which turn into coarser sandy tidal flat deposits toward the top. Sandy tidal flat deposits are overlain by washover sheet and washover fan deposits. The second model demonstrates a barrier spit accretion through southerly directed progradation. Eroded sediment was transported along the west coast of Sylt by longshore drift and was added to the southern spit-end. Progradation and barrier spit accretion were interrupted by severe storm surges. Storm surge generated erosion unconformities in a foreshore to shoreface environment redraw old spit-end positions that represent stages of barrier spit progradation.

Das Verbundprojekt SIMULTAN erforscht die Früherkennung für Instabilität, Unruhe und Kollaps von Erdfällen. Der neuartige Forschungsansatz kombiniert strukturelle, geophysikalische, petrophysikalische und hydrologische... more

Das Verbundprojekt SIMULTAN erforscht die Früherkennung für Instabilität, Unruhe und Kollaps von Erdfällen. Der neuartige Forschungsansatz kombiniert strukturelle, geophysikalische, petrophysikalische und hydrologische Kartierungsmethoden, die von Sensorentwicklung und mulit-skaliger Überwachung flankiert werden, und umfasst eine Informationsplattform. Kollapsprozesse an Erdfällen finden generell in den obersten wenigen 100 Metern der Erdkruste statt. Individuelle Prozesskomponenten können einfach sein und verstanden werden. Aber es wechselwirken auch Prä-Kollapsprozesse und Vorläufer auf unterschiedlichen raum-zeitlichen Skalen und mit kleinen Variationen miteinander. Dies erfordert innovative, multi-skalige Beobachtungen, Analysen und integrierte Früherkennungskonzepte, besonders für urbane Bereiche, die bisher noch nicht vollständig entwickelt verfügbar sind und auch noch nicht als automatische operationelle Systeme arbeiten. Zur Identifizierung und Quantifizierung von Subrosionsbereichen zeigten sich bohrlochseismische Verfahren mit kombinierten P- und S-Wellen als zielführend. Als besonderer Indikator, der sich auch für Langzeitmonitoring eignet, hat sich dabei das ungewöhnliche Konversionsverhalten der Wellen in Subrosionszonen gezeigt. Neue Prozessingverfahren zur Detektion kleiner seismischer Ereignisse und für emergente Einsätze unterstützen den Ansatz von angepassten Arraymessungen. Geodätisch-gravimetrische Überwachungsnetze sind auch unter urbanen Bedingungen geeignet, durch Subrosion verursachte Oberflächendeformationen und Massenverlagerungen räumlich-zeitlich zu erfassen und zu überwachen. Nivellements liefern bezüglich der Oberflächendeformation höchste Genauigkeiten; zugleich sind sie vergleichsweise kostengünstig zu realisieren. Die Integration von GNSS hat in Verbindung mit dem Nivellement die räumliche Auflösung im Untersuchungsgebiet zusätzlich gestützt und hat das Potenzial, diese großräumig zu kontrollieren. Gravimetrische Messungen sind mit einem sehr hohen Aufwand verbunden. Die Kombination oberflächengeophysikalischer Verfahren mit einer vertikal hochaufgelösten direct push-basierten Erkundung im Raum mit einem maßgeschneiderten hydrogeologischen Monitoring bietet eine zuverlässige Grundlage für numerische Prozessmodellierungen und ermöglichen es, erdfallrelevante Prozesse abzubilden und zu erfassen. Karstaquifer- und geomechanische Modellierungen konnten die Prozesse in den Fokusgebieten erfolgreich abbilden, sobald diese mit realistischen Werten unterlegt wurden. Es zeigt sich somit insgesamt, dass sowohl flächenhafte Messungen und zeitlich wiederholte Kampagnen sehr vorteilhaft sind, da sie es erlauben, Fehler zu verringern und beanspruchte Bereiche einzugrenzen. Erst dieses integrierte Vorgehen ermöglicht es, potenzielle Wegsamkeiten im Untergrund hochauflösender als bisher abzubilden und zu bewerten. Als solches stellt es ein Instrumentarium zur Charakterisierung und angepassten Überwachung von Untergrundbereichen im Allgemeinen zur Verfügung. Diese Ergebnisse und Szenarien stehen der Öffentlichkeit auf einer Informationsplattform zur Verfügung (http://simultan.gfz-potsdam.de).

Telah dilakukan penelitian struktur patahan di Sungai Cinambo, Jatigede, Jawa Barat (9/05/15). Penelitian ini bertujuan untuk mengidentifikasi struktur geologi serta nilai strike dan dip batuan di sepanjang Sungai Cinambo. Dari pengukuran... more