Second Vertical Derivative Research Articles

Identification of Fault Poso Earthquake Causes 2017 Mw 6.6 with Gradient Vertical Gravity Satellite Imagery

May 29, 2017 a devastating earthquake occurred in the district of Poso, Central Sulawesi. This earthquake can be affected significantly by the people. Based on the analysis of the source mechanism, an earthquake caused by a normal fault around the graben zone of Palopo. The purpose of this research is to identify Earthquake-causing fault of Poso 2017 Mw 6,6 by using Second Vertical Derivative (SVD) analysis of gravity. The result of profiles line that bypass the alleged fault orientation indicates the existence of normal fault structure indicating the absolute value of the minimum SVD anomaly is relatively smaller than the maximum SVD anomaly value in the epicenter zone of the earthquake.

Second Vertical Derivative Using 3-D Gravity Data for Fault Structure Interpretation

Derivative calculation of potential field for signal enhancement is common to be applied in order to provide geologic interpretation. Second Vertical Derivative (SVD) can be used to estimate fault structure and also tends to emphasize shallower geologic anomalies. In this work, we evaluate SVD results using 2-D and 3-D gravity data from two synthetic models (combination of two faults at different depth). Horizontal grid stations designed in the flat surface with 100 m interval for 2-D synthetic data calculation, while 3-D synthetic data calculation designed with addition of 50 and 100 cm in vertical levels (above each surface grid stations). Comparison SVD calculation using 2-D and 3-D synthetic gravity data conducted to perform the possibility of combined gradient interpretation proceedure. SVD from real data aplication identify 2 normal fault with (NE-SW trend) and 1 reverse fault (with NW-SE trend).

Surface and subsurface structures of Kalabsha area, southern Egypt, from remote sensing, aeromagnetic and gravity data

Kalabsha area is known to be the most seismo-active zone at the southwestern region of the Aswan High Dam, in southern Egypt. The main purpose of this work is the analysis and interpretation of satellite imagery, aeromagnetic and ground gravity data of Kalabsha area in order to reveal the subsurface lithology and structure. The Landsat ETM+ data were produced in a false-color composite image (bands 1, 2 and 3 in RGB) at the same scale as the geological map in order to reveal some extra geological and structural features. An attempt has been made to analyse the complex nature of gravity and magnetic anomalies over the Kalabsha area to reveal their relationship with surface geology, structure and tectonics setting. These analyses include isolation of anomalies into regional and residual components using the band-pass filter, second vertical derivatives (SVD), upward continuation, and shadowgrams technique. It was noticed that, there is close correlation between gravity, magnetic and many of the major surface geological features of the region. The basement structural map of Kalabsha area has been prepared from the integration of SVD of regional component maps of both gravity and magnetic. The interpretation of the basement tectonic map of the area indicated the presence of two sets of faults NNW–SSE to N–S which is dissected by an E–W to WNW–ESE fault system. These two sets of fault systems as deduced from the gravity and aeromagnetic data were found to match well with that obtained from the Landsat image and geological map.

Magnetic interpretation of north Gebel El Shallul area, central Eastern Desert, Egypt

The present work utilizes the aeromagnetic data supported by geology and remote sensing satellite data, to delineate surface and subsurface structural elements in north Gebel El Shallul area. Geologically, the area is covered by Precambrian basement rocks to the East (metasediments, metavolcanics, Hammamat sediments and younger granites) and Phanerozoic sediments to the West (Nubian Sandstones and Qouseir clastics). The Landsat image of the area gave additional detailed litholgic information which is very useful in identifying and discriminating the different lithologic rocks exposed in the area. Analysis of the structural lineaments of the Landsat image and the compiled geological map show that most of the well-developed structural lineaments have NW, NNW and ENE trends. The aeromagnetic data were analyzed and processed by several advanced techniques; reduction to the pole, regional-residual separation, second vertical derivative (SVD), analytical signal, Euler deconvolution and shadowgrams. The application of local power spectrum on the reduced to North Pole (RTP) aeromagnetic data indicated that the average depths to the near–surface and deep-seated causative magnetic bodies were found to attain 0.5 and 1.8 km, respectively. Therefore, the filtering of the aeromagnetic data at the two assigned interfaces was conducted to assist the discrimination of the residual (near-surface) and regional (deep–seated) magnetic anomalies. The prepared aeromagnetic maps have been interpreted qualitatively and quantitatively to deduce the structural elements which were used to construct a basement tectonic map for the area. The used analysis techniques helped to reveal many structural elements such as faults of different orders, uplifted blocks (antiforms or horsts) and subsided blocks (basins or synforms). It has been found that the NNW pronounced linear magnetic anomalies, normally and reversely magnetized, are associated with deep-seated diabasic dykes. The interpretation of the basement tectonic map of the area indicated the presence of a set of unexposed subsurface basic dykes running generally in NNW–SSE direction controlling the courses of major wadis in the study area. This set of NNW–SSE basic dykes are dissected by a NE–SW fault system. These two sets of fault systems were found to be matched well with that obtained from the Landsat image and geological map. It was found that the pronounced NNW direction is a predominant structural trend controlling the structural framework of the area.

Accommodation zones and tectono-stratigraphy of the Gulf of Suez, Egypt: A contribution from aeromagnetic analysis

ABSTRACT This paper starts with an up-to-date literature review of the pre-rift, syn-rift and post-rift stratigraphy of the Gulf of Suez. The geometry and depth of the Proterozoic basement is not generally known due to poor seismic images below the Upper Miocene evaporites (including massive rock salt) and clastics. The pre-rift Paleozoic to Early Oligocene succession shows that several local basins (c. 10s of km in extent) occur in the Gulf, with thick sedimentary sections (e.g. c. 3,000 m for Paleozoic and 1,000 m for Jurassic and Lower Cretaceous). The origin and distribution of these basins is not well understood and the presence of similar pre-rift basins in the southern Gulf is not known to occur. The syn-rift Late Oligocene to Middle Miocene and post-rift Late Miocene – Pliocene successions are widely distributed within the rift basin and reach a thickness in excess of 5,000 m. In order to visualize the grain and relative relief of the Proterozoic basement, a series of aeromagnetic images are shown in this paper. The images include Total Magnetic Intensity (TMI), Reduced-to-Pole (RTP), filtered regional and structural RTP, and Second Vertical Derivative (SVD). The paper also shows a three-dimensional visualization image of the magnetic basement that highlights the distribution of the basins in the Gulf. The magnetic lows do not generally trend along the Suez (NNW-trending Clysmic) Fault, but instead show highly variable orientations attributed to a complex pattern of criss-crossing faults. In particular, two areas were selected to interpret the geometry and depth of the basement. The first area covered the northern Zaafarana Accommodation Zone and involved modeling five aeromagnetic profiles. The Zone was interpreted as an EW-trending basement plateau bounded by basins that are c. 8,000 m deep. The second modeled area (four profiles) covered the southern Morgan Accommodation Zone. This zone was interpreted as an ENE-trending plateau of similar relief to the Zaafarana Zone. The Morgan Zone is terminated in the eastern Gulf by the 8,000-m-deep Morgan Basin. The very deep basins surrounding the two plateaus may contain both pre-rift and syn-rift source rocks, from which the numerous surrounding petroleum fields were sourced.

Spatial correlation of the aeromagnetic anomalies and seismogenic faults in the Marmara region, NW Turkey

Previous investigations into the deep structure of the Marmara Sea region revealed an existence of a rigid barrier located at the centre of the Marmara Sea. Thus, the North Anatolian Fault (NAF) was divided into three segments to the west of this barrier. Seismological records of two 5 year periods (1998–2002 and 2003–2007) indicate a decrease of seismic activity on and around this barrier. It was previously shown if the fault movement reaches to magma its fractures are filled with magmatic material causing magnetic anomalies. In this study, advance processing methods are utilized to observe the spatial correlation between the aeromagnetic anomalies and the faults of the Marmara region. These are the reduction to the pole transformation (RTP) and second vertical derivative (SVD) methods. In particular, SVD map shows alignments which can be correlated with the faults. These faults are the Northern Boundary, Yalova, Armutlu, Imrali and Edincik faults. Length of the Northern Boundary Fault (NBF) is about 50–60 km. Thus, this fault would not produce strong earthquakes. The Edincik Fault extends from east to the west and bends through WSW. The length of this fault in connection with the Imrali, Armutlu and Yalova faults in the east exceeds 300 km and named the Main Fault Zone (MFZ) by the authors of this study. These faults as a whole may produce strong earthquakes. Some seismic gaps are observed along with the Imrali and Edincik faults from the earthquake distribution records of two 5 year periods (1998–2002 and 2003–2007). As a conclusion, there are high-potentials of strong earthquake occurrences in these regions.

Abstract: Well Data Projection into Undrilled Exploration Areas Using Gravimetric and/or Seismic Isochore Steering Functions 

ABSTRACT Regional deposystem maps offer insight into reservoir distribution in space and time. They can be valuable tools for exploration, yet their full potential for predicting reservoir quality ahead of the drill bit is limited by the location, quality and congruity of stratigraphic well control. Maximizing the impact of control data that may be abundant but spatially restricted, and improving the value of reservoir property prediction in undrilled areas are the principal objectives of this study. To this end, ordinary stratigraphic rationale was encoded to: 1) check the reliability of stratigraphic event data from many sources (in-house paleo; MMS tops; sequence stratigraphic studies; etc.); 2) determine an optimum stratigraphic record for each well by intelligently dealing with out-of-order events (remove; infer an unconformity; infer sub-salt; etc. ); 3) assign standardized ages to the optimized well records; and, 4) compute deposystem parameters suitable for gridding, e.g., uncorrected interval accumulation rate. Parameters such as accumulation rate are based on selected chronostratigraphic intervals (e.g., 23.0 MY - 24.0 MY) rather than on restricted, and not always equivalent events of variable nomenclature populating typical decades-old databases, e.g., Liebusella top, Cyclicargolithus abisectus top, etc. The less restrictive canonical intervals maximize available well control for all standard bio- /litho-stratigraphic units, permit the selection of arbitrary synoptic units, and provide an optimal base upon which to apply gridded steering operators to guide deposystem map extension into areas of limited well control. Steering operations may be performed in most of the popular gridding and mapping software packages. Second vertical derivative (SVD) gravity, i.e. density-driven steering of deposystem data into rank exploration areas is currently favored in the salt canopied northern Gulf of Mexico where geologically reasonable deposystem and sand maps have been generated. Seismic isochron steering is favored for exploration applications in unconfined basinal deposystems.