Showing papers on "Magnetic dip published in 2008"

Electromagnetic wave resistivity tool having a tilted antenna for determining the horizontal and vertical resistivities and relative dip angle in anisotropic earth formations

Abstract: This invention is directed to a downhole method and apparatus for simultaneously determining the horizontal resistivity, vertical resistivity, and relative dip angle for anisotropic earth formations. The present invention accomplishes this objective by using an antenna configuration in which a transmitter antenna and a receiver antenna are oriented in non-parallel planes such that the vertical resistivity and the relative dip angle are decoupled. Preferably, either the transmitter or the receiver is mounted in a conventional orientation in a first plane that is normal to the tool axis, and the other antenna is mounted in a second plane that is not parallel to the first plane. Although this invention is primarily intended for MWD or LWD applications, this invention is also applicable to wireline and possibly other applications.

A non-linear geodetic data inversion using ABIC for slip distribution on a fault with an unknown dip angle

Abstract: SUMMARY We have developed a method of geodetic data inversion for slip distribution on a fault with an unknown dip angle. A common strategy for obtaining slip distribution in previous studies is to first determine the fault geometry by minimizing the square misfit under the assumption of a uniform slip on a rectangular fault, and then apply the usual linear inversion technique to estimate a slip distribution on the determined fault. It is not guaranteed, however, that the fault determined under the assumption of a uniform slip gives the best fault geometry for a spatially variable slip distribution. The inverse problem is non-linear for cases with unknown fault geometries, but the non-linearity of the problems is actually weak, when we can assume the fault surface to be a flat plane. In particular, when a clear trace of coseismic faults is observed on the Earth’s surface, only the dip angle is an unknown parameter to determine the fault geometry. Then, we regarded the dip angle as an hyperparameter that prescribed the structure of parametric models, and obtained the best estimate of the dip angle using Akaike’s Bayesian Information Criterion (ABIC). With the best estimate of the dip angle, we can obtain the slip distribution on the fault based on the maximum-likelihood principle. We applied the method to the InSAR data of the 1995 Dinar, Turkey earthquake and obtained a much lower dip angle than the previous analyses.

Simple relationship between seismic activity along Philippine Sea slab and geometry of oceanic Moho beneath southwest Japan

Abstract: SUMMARY Many earthquakes with various types of focal mechanisms occur along the subducting Philippine Sea slab (PHS) beneath southwest Japan, and the hypocentre distribution is quite inhomogeneous. In this region, distinct non-volcanic deep low-frequency tremors are often observed. To clarify the cause of these apparently complicated and peculiar seismic activities, we first construct a detailed configuration of the oceanic Moho (slab Moho) within the PHS based on a receiver function (RF) analysis. To convert the time-domain RFs into their depth-domain equivalents, we adopt a fine-scaled velocity model based on the traveltime tomography. The depth contours of the oceanic Moho exhibit complexities, but the active region of the intraslab earthquakes corresponds well to the oceanic Moho geometry. In the western part of Shikoku, the intraslab seismicity is very high and the focal mechanisms mainly exhibit normal faults with east‐west extension axes. Since the PHS is subducting to the west and the dip angle of the slab becomes steep in the western part of this region, the stress field in this region can be attributed to the slab pull induced by the westwards slab subduction. Similar types of focal mechanisms are observed in the Tokai district with a focal depth greater than 35 km. Since the oceanic Moho exhibits a ridge shape in this region, its stress field can be attributed to the slab pull and the effect of slab bending. Shallow earthquakes in the Tokai and eastern Shikoku regions have strike-slip focal mechanisms and their extension axes are parallel to the strike of the oceanic Moho. These focal mechanisms may be influenced by both the oblique subduction of the slab and low slab dip angle. Earthquakes beneath the Kii Peninsula exhibit strike-slip or downdip compression focal mechanisms with east‐west compression axes. Since the Moho beneath this peninsula shows a valley shape, compressional stress occurs around the Moho. Moreover, the slab convergence compresses this valley. This also induces the east‐west compression field in this region. We have newly confirmed the existence of an aseismic slab beneath the northern part of the Kinki district, central part of Japan. In this aseismic region, the dip direction of the slab is parallel to that of the slab convergence direction. This tendency is observed in the central part of Shikoku, where the slab seismicity is relatively low. These features imply that the intraslab seismicity is constrained by the interaction between the slab geometry and slab motion. We also revealed the possibility that the oceanic Moho beneath not only Ise Bay but also the Kii Channel has a ridge shape. In both these regions, the non-volcanic low-frequency tremor activity becomes low. More than 80 per cent of the tremor epicentres are distributed within contour depths of 38 ± 3 km of the oceanic Moho. We find that the interaction between the Moho geometry and the plate motion of the subducting PHS plays an important role in determining the local stress field and the location of both seismicity and low-frequency tremors.

Structural features of the subducting slab beneath the Kii Peninsula, central Japan: Seismic evidence of slab segmentation, dehydration, and anisotropy

Abstract: [1] Seismic evidence of lithospheric slab segmentation, dehydration, and anisotropic rocks beneath the Kii Peninsula, central Japan, is detected with receiver function (RF) analyses. By stacking radial and transverse RFs with moveout perturbations, we estimate the downdip azimuth, dip angle, and depth of the slab Moho beneath each seismic station. Comparing the downdip azimuth to the slab convergence azimuth, we can classify the slab into three segments. The segments correspond to both the fault zones of past megathrust earthquakes and to the spatial distribution of intraslab seismicity. The slab Moho lies just above the intraslab seismicity in the southwestern Kii Peninsula. Slab Moho lies deeper at the eastern part of the peninsula, at the bottom of seismicity. This suggests that earthquakes occur only within the slab mantle under the southern Kii Peninsula. The dip angle of slab Moho becomes steeper at 40- to 50-km depth, perhaps caused by dehydration transformation of basalt to eclogite. At some stations located in the western part of the Kii Peninsula, RF-estimated dip angle of the interface is much steeper than that estimated by spatial trends in seismicity. Since the local seismicity distribution reflects well the larger-scale geometry of the slab, the RF-estimated dip angle may imply anisotropic wave speeds within strongly sheared and/or hydrated media around the slab Moho. These detailed features of the slab may be one key in distinguishing the source regions of megathrust earthquakes in the Nankai region.

Tenebrio beetles use magnetic inclination compass

Abstract: Animals that guide directions of their locomotion or their migration routes by the lines of the geomagnetic field use either polarity or inclination compasses to determine the field polarity (the north or south direction). Distinguishing the two compass types is a guideline for estimation of the molecular principle of reception and has been achieved for a number of animal groups, with the exception of insects. A standard diagnostic method to distinguish a compass type is based on reversing the vertical component of the geomagnetic field, which leads to the opposite reactions of animals with two different compass types. In the present study, adults of the mealworm beetle Tenebrio molitor were tested by means of a two-step laboratory test of magnetoreception. Beetles that were initially trained to memorize the magnetic position of the light source preferred, during the subsequent test, this same direction, pursuant geomagnetic cues only. In the following step, the vertical component was reversed between the training and the test. The beetles significantly turned their preferred direction by 180°. Our results brought until then unknown original findings that insects, represented here by the T. molitor species, use—in contrast to another previously researched Arthropod, spiny lobster—the inclination compass.

Method for measuring ground stress

Abstract: The present invention relates to a ground stress measuring method which comprises the following procedures: 1) the occurrence of joint and faultage are determined; the nearest sequent subjoint and fissure in the same sequence are drawn on a stereographic projection drawing; 2) a terrane lay uses the strike line as a rotating axis and rotates to the horizontal position towards the dip direction; the rotary angle is equal to a dip angle of the lay, and the strike line of the joint and fissure winding lay rotates to the horizontal state to find a conjugated X-shaped joint; then the conjugated X-shaped joint and lay in the horizontal state rotate to the original state; three directions of the ground stress are determined on the stereographic projection drawing; 3) samples are drilled along three directions of the ground stress and 5 to 7 samples are drilled along each direction; 4) the acoustic emission experiment of a rock sample is done indoors to have a Db4 small wave analysis on the acoustic emission signals of rock, thereby determining the acoustic emission Kaiser point of rock; the size of the ground stress is determined according to the acoustic emission Kaiser point of rock. The invention is small in sample quantity, low in cost, rapid in measuring progress of the ground stress, and accordingly more convenient and rapid in measurement of the ground stress.

Anisotropic correction of sonic logs in wells with large relative dip

Abstract: Seismic reservoir characterization and pore-pressure prediction projects rely heavily on the accuracy and consistency of sonic logs. Sonic data acquisition in wells with large relative dip is known to suffer from anisotropic effects related to microanisotropy of shales and thin-bed laminations of sand, silt, and shale. Nonetheless, if anisotropy parameters can be related to shale content Vsh in siliciclastic rocks, then I show that it is straightforward to compute the anisotropy correction to both compressional and shear logs using Vsh and the formation relative dip angle. The resulting rotated P-wave sonic logs can be used to enhance time-depth ties, velocity to effective stress transforms, and low-frequency models necessary for prestack seismic amplitude variation with offset (AVO) inversion.

Surface rupture,thrusting and strike-slipping in the Wenchuan earthquake of Sichuan,China

Abstract: The Ms.8.0 huge earthquake of May 12th,2008 occurred in Yingxiu-Beichuan fault of Longmen Mountains belongs to a thrusted-strike-slip type.By laying emphasis on the geomorphic features of the surface ruptures of the huge earthquake in Longmen Mountains on the eastern margin of Qinghai-Tibet Plateau,this paper confirms the vertical and horizontal offsets of the Yingxiu-Beichuan fault and the Pengxian-Guanxian fault by detailed field geomorphic surveys.The authors have measured surface ruptures and cracks,such as terrace offset,scarp,fault-controlled saddles,dextral shutter ridges,dextral channel offsets,graben,shatter belt,fluvial fans offset,highroad offsets,tectonic cracks,press ridges and slope trench in some key positions.The result indicate that the surface rupture of the Wenchuan earthquake stretches to NEE direction which strikes NE 30°~50°and trends NE with a dip angle 30°~40°.The surface rupture of the Yingxiu-Beichuan fault stretches 180~190 km from Yingxiu to NE.It belongs to a single side-multi-dots type characterized by some dextral strike-slip thrusts with steep dip angles of 1.60~6.00 m vertical offsets and 0.20~6.50 m horizontal offsets.And the surface rupture of the Pengxian-Guanxian fault can be observed between Cifengchang of Pengzhou and Hanwang of Mianzhu.It is 30~40 km long and has some dextral strike-slip thrusts with slight dip angles of 0.39~2.00 m vertical offsets and 0.20~0.70 m horizontal offsets.These evidences indicate that the surface ruptures are thrusts with dextral strike-slip and thrust displacements.The thrust displacement are equal to or slightly bigger than the dextral strike-slip displacements.According to the historical earthquakes and active tectonic geomorphic dating data,the authors think that there has been and wil be a strong earthquake every 1~3 ka at this fault.Based on this,the authors set a dynamical model to illustrate the possible links between surface processes and upward extrusion of lower crustal flow on the eastern margin of the Qinghai-Tibet Plateau and conclude that the vertical press and motions of lower crust materials result in the thrust motions of the Longmen faulted zone to east,the tectonic uplift of Longmen Mountains and the huge Wenchuan earthquake.

Fault model of the 2007 Noto Hanto earthquake estimated from PALSAR radar interferometry and GPS data

Abstract: The 2007 Noto Hanto earthquake (Mw 6.6) is the first major earthquake in inland Japan since the launch of the Japanese ALOS satellite. Interferometric synthetic aperture radar successfully mapped the coseismic displacements from both ascending and descending orbits in and around the earthquake epicentral region. The line-of-sight displacements toward the satellite from the ascending and descending orbits amount to about 50 and 20 cm, respectively. The interferograms as well as the GPS data of the GEONET network are inverted in order to determine the slip distribution on the source fault. The dip and strike angles of the preferred model are 48° and N51°E, respectively, and its fault slip area reaches the seafloor. The dip angle is not well constrained in our tested range between 40° and 60°. The dominant slip area is located just above the hypocenter, at depths between 4 and 10 km. Many aftershocks seem to have occurred on and around the area of dominant slip.

Study on genetic mechanism of translational landslide

Abstract: According to the physico-mechanical parameters of the Tiantai Village landslide,the physical simulation was preformed. The deformation and failure evolution of the translational landslide,which is caused by the cooperation of the hydrostatic pressure and the uplift pressure,are reconstructed. The clear relationship between the critical water head and the dip angle of the sliding plane is revealed by the results:the larger the dip angle of the slide plane is,the smaller the critical head would be under the same physico-mechanical parameters of rock and soil in the landslide,and vice versa.

Measurement of a Linear Energy Transfer Distribution with Antioxidant Doped CR-39 Correcting for the Dip Angle Dependence of Track Formation Sensitivity

Abstract: Antioxidant doped CR-39 detectors were loaded onto the STS-95 space shuttle mission (altitude: 574 km; inclination: 28.45°; flight duration: 8.9 days) for measuring the linear energy transfer (LET) distribution above 10 keV/µm for space radiation dosimetry. It is known that the track formation sensitivity of antioxidant doped CR-39 detectors depends on the dip angle of the incident particle. We investigated this dip angle dependence for a wide range of LET values and dip angles. The track formation sensitivities at lower dip angles were obviously decreased in the LET region below 100 keV/µm. We introduced minimum-cutoff dip angles in order to correct for such dip-angle dependence. The LET distribution of the STS-95 mission was obtained from the measurements of etch pits having dip angles larger than the minimum-cutoff dip angles. This new correction method increased the absorbed dose and dose equivalent above 10 keV/µm by 54 and 28%, respectively.

Modelling Pressurized Deformation Source for Changbaishan Volcano with Homogenous Expansion Point Source

Abstract: In view of the fact that the horizontal displacements in Changbaishan volcanic region during 2002~2003 lacked centric symmetric distribution caused by spherical pressurized magma chamber, three mutually orthogonal tensile point sources at the same depth are used to simulate the pressurized deformation source in the volcano region. In a homogenous elastic half-space with media parameters of Vp=6.700 km/s, Vs=3.8700 km/s, and ρ=2900 kg/m3, GPS and leveling data during 2002~2003 are jointly used to invert for the pressurized deformation source in Changbaishan volcanic region with PSGRN/PSCMP code and genetic algorithm. The results show that an ellipsoid point source model composed of unequal tensile ones in three orthogonal directions can represent the magma chamber in Changbaishan volcanic region. The magma chamber is located in about 9.2 km depth, the largest volume expansion is up to 7.0 × 106 m3 in the direction normal to the fault plane with strike angle 34.4° and dip angle 82.2°, the second one is 6.6 × 106 m3 in the direction normal to the fault plane with strike angle 302.8° and dip angle 78.5°, the last one is 5.2×106 m3 in the direction normal to the fault plane with strike angle 337.7° and dip angle 14.0°.

Himalayan ultrahigh pressure rocks and warped Indian subduction plane

Abstract: In this paper, we will use the knowledge of ultrahigh-pressure (UHP) metamorphic evolution as independent data to constraint the geometry and reconstruct the tectonic evolution of the early stage of the India-Asia collision. The two UHP units recognized in NW Himalaya (Kaghan in Pakistan and Tso Morari in India) belong to distal parts of the continental Indian margin subducted between 55 and 45 Ma at a minimum depth of 100 km (e.g. Guillot et al. 2003 for review), evolving simultaneously during the early Himalayan evolution. They are interpreted as the signature of the early subduction of the Indian continental plate at the Paleocene-Eocene boundary. The metamorphic conditions are synthesized in Table 1 for both units. Even if similar protoliths are involved and both UHP units record the same maximum depth of about 100 km, some differences in P-T-t conditions may be emphasized. Firstly, the temperature of the metamorphism peak is significantly lower than a minimum of 100°C in the Tso Morari unit suggesting that the subduction rate is higher (Peacock 1992) in the Eastern part. Secondly, the western Kaghan unit seems to be involved in the subduction zone 4 Ma (~ 53 Ma) after the Eastern Tso Morari unit (~ 57 Ma). The later implication of the Kaghan unit in the subduction zone is related to its greater internal localization on the Indian margin, which, combined with a lower subduction rate, induce a higher temperature peak. As the UHP units are buried and exhumed along the subduction plane (e.g. Chemenda et al. 2000), the dip angle of the subduction plane can be deduced from the geometry of the subduction and the timing of the processes. The sinus of dip angle is equal to the amount of vertical displacement (D) during an interval of time, divided by the amount of Indian plate subduction during the same time interval (H). Those two data are independently measured, D from the exhumed rocks, H from the motion of the Indian plate.

Manifestations of weihe fault at deep,middle,shallow and near-surface depth

Abstract: The Weihe Fault is an important blind fault in Weihe Basin and controls the formation,evolution and seismicity of Weihe Basin. The deep seismic reflection survey results show that the fault is not a deep crustal fault; it is located right below the C layer at about 15km depth and cuts through the crystalline basement and the C layer,causing a throw of about 4km between the two sides of crystalline basement. The dip angle at the shallow part of the fault(depth5km)is big and flattens with depth,and the fault turns to be a listric fault.Shallow seismic survey results show that the dip angle of the Weihe Fault in the middle and deep parts is about 85°; the attitude is different on the two walls of the fault,the footwall is horizontal and the hanging wall is tilting to the south direction; and its dip angle increases quickly.Drilling survey results show that the fault at the shallow part is obviously manifested. The lithology,thickness and attitudes of strata are quite different between the two sides of fault. The attitude on the footwall is horizontal and that on the hanging wall tilts a bit to the fault side. The late Pleistocene displacement is about 4～6m.Trenching results show that the Weihe Fault near ground is still active. Since Holocene epoch it has undergone 3 paleoearthquakes and 1 history earthquake,so it is a Holocene active fault.

Fault slip and modern tectonic stress field in and around Kunming basin

Abstract: Kunming basin is a Cenozoic faulted basin under the control of mainly SN-trending active faults. In and around the basin, there are a total of eight major active faults. Seismo-geological survey and fault slip observation show that the SN-and NE-trending active faults are mostly sinistral strike-slip faults, while the NW-trending faults are mostly dextral strike-slip faults. Using stress tensor inversion method with 706 active fault striation data at 22 measurement sites, we determined tectonic stress field of the study area. The result shows that modern tectonic stress field in and around Kunming basin is characterized by NNW-SSE compression, ENE-WSW extension, and strike-slip stress regimes. The maximum principal compressional stress (σ1) is oriented 335°–2°, with an average dip angle of 21°; the minimum (σ3) is oriented 44°∼93°, with an average dip angle of 14°, and the intermediate (σ2) has a high, or nearly vertical, dip angle. The inversion result from fault slip data is consistent with the result from focal mechanism solutions.

A Model Study on Deformability of A Transversely Isotropic Rock

Abstract: In the uniaxial compressive test of a single specimen of transversely isotropic rock, its 5 independent elastic constants can not be defined since maximum 4 independent strain measurements are available theoretically. In order to solve this problem, one equation proposed by Saint Venant in 19C and confirmed by Lekhnitskii through the test experiences has been used for long time. Accordign to authors' experiences, however, this equation turned out to give erroneous elastic constants in some cases. Three new equations are suggested and their compatibilities are discussed in this paper. As the results of the analyses of the models, Lekhnitskii's suggested equation is effective for the specimen with the high dip angle whereas it results in the large erred output for that with dip angle less than . It was found that the effectivenesses of three suggested equations and their compatibilities are subject to the dip angle and not to the amounts of elastic constants. Guide map to the selection of the compatible one of those suggested equations is presented as a result of the study.

Zircon U-Pb Geochronology of the Shangma Fault,Dabie:Constraints on the Transformation from Ductile to Brittle Deformation,and Its Significance to the Tectonic Evolution of Dabie Orogenic Belt

Abstract: According to the particular investigations on the geometry and kinematics of the Shangma fault,three different crust-levels of extension movements have been differentiated in sequence of development from the deep to the shallow:① ductile shearing with top to the NWW in low dip angle;② brittle or brittle-ductile transition normal fault with top to the NWW in low dip angle;③ brittle normal fault with top to the NWW in high dip angle.Two samples were chosen for zircon U-Pb age dating to test the constraints on the activity age of the Shangma fault.A bedding intrusive granitoid pegmatite vein which was parallel to the foliation of the ductile shear zone of the country rock which exhibits a boudinage deformation,showing syn-tetonic emplacing at the end of ductile deformation period and deformation in the brittle-ductile transition domain.The zircon U-Pb age dating of the granitoid pegmatite vein gives a result of 125.9±4.2 Ma,expressing tie extension age in the brittle-ductile transition domain of the Shangma fault.Another sample,which was collected from a granite pluton cutting the foliation of the extension ductile shear zone,gives a zircon U-Pb age of 118.8±4.1 Ma,constraining the end of the ductile shearing.Then the transformation time from ductile to brittle deformation can be constrained at 126-119 Ma.Compared with the former researches,the formation of the Luotian dome,which is located to the east of the Shangma fault can be constrained at 150-126 Ma.This study offers a new time constraint to the evolution of the Dabie orogenic belt.

Apparatus for measuring object dynamic obliquity

Abstract: The utility model provides a measuring device for object dynamic dip angle, which relates to the measuring technique field, aiming at solving the measuring technique problem of object dynamic dip angle. The measuring device comprises an accelerometer for measuring acceleration components aX, aY, a data wireless transmission part with a radio frequency transmitting module and a radio frequency receiving module, a calculation part for realizing serial communication with a wireless receiving end, a calculation part from acceleration to angle and dynamic dip angle for curve drawing, a calculation part for dynamic dip angle and an interface RS232 for connecting the computer and the wireless receiving module; the calculation program of computer can make use of the formula Theta x =5.8480 ay - 0.4006 r, Theta y =5.8480 ax - 0.4006 r to compute a dip angle of an object in real time and to draw out a corresponding curve. The utility model is characterized by low developing cost, long transmission distance, being capable of taking advantage of computing acceleration to calculate object dynamic dip angle and realizing real-time wireless remote measuring for dynamic dip angle of a local object.

Inclination angle measuring apparatus of digital display horizontal deflection gage

Abstract: The utility model relates to a dip angle measuring device of a digital display horizontal dipping compass. According to the technical proposal provided by the utility model, a main shaft is transversely arranged inside a main support and is in slide connection with the main support; one end of the main shaft is fixed with a circular capacitive-gate moving gate; a main cover opposite to the circular capacitive-gate moving gate is fixed with a circular capacitive-gate static gate; the other end of the main shaft is provided with a non magnetic metal single pendulum; the circular capacitive-gate moving gate and the circular capacitive-gate static gate are arranged at intervals, and are formed into a dip angle measuring component; the main support is provided at intervals with a left magnet and a right magnet; and a working section of the single pendulum is inserted between the left magnet and the right magnet. The dip angle measuring device has high measuring precision and short measuring time; moreover, a user can visually read a dip angel numerical value relative to horizontal direction.

Inclination angle measurer of digital display leveler

Abstract: The utility model relates to a dip angle measurer of a digital display level bar. According to the technical proposal provided by the utility model, a main shaft which is arranged on a support casing is provided with an electric brush support plate with disc code of coupled arrangement, a damping impeller inducer and a single pendulum; the impeller inducer at least has two symmetrically arranged damping fan blades; the electric brush support plate is provided with an electric brush; and the rotation of the electric brush can generate a swing angle digital signal which is processed by an electronic system so as to obtain a dip angle numerical value. The dip angle measurer has simple structure and low manufacturing cost, and ensures accurate measurement and short reaction time when used.

Study on Anti-skid and Anti-collapse Measures of Hydraulic Support Used in Large Dip Angle Mining Face

Abstract: In large dip angle mining face,the antis-kid and anti-collapse question on hydraulic support is a key to mining successfullyAnalyzes the reasons of declining and falling of hydraulic support used in large dip angle face,and studies on anti-skid and anti-collapse technology of support,presents the anti-skid and anti-collapse measures of hydraulic support used in large dip angle mining face,and gives ZF4800/18/26 support as an example to prove that the anti-skid and anti-collapse measures are feasible

The characteristics of the laoyachen fault in zhengzhou revealed by shallow seismic data of p wave and s wave

Abstract: The investigation and study of fault activities are a basic work for urban earthquake prevention and disasters reduction.In order to find out the location,characteristics and activities of the Laoyachen Fault in Zhengzhou,the high-resolution shallow seismic P and S wave survey profiling across the Laoyachen Fault was carried out at the end of 2006,and different seismic sources along with combinations of diverse observation geometries with different parameters were used.The fine structures in different depths beneath the profile were obtained and the patterns as well as characteristics of the Laoyachen Fault were determined.The results show that the Laoyachen Fault,running in NW and dipping in NE,is a normal fault and its dip angle is about 60°～70°,which incises strata of Eocene,Permian,Carboniferous or Ordovician epoch and goes up to the top boundary of Eocene stratum at the 800～850m depth.There is no any reflector of offset stratum found in Q+N strata.The borehole geological sections across steep slopes of earth surface present that the layers inferred from reflected seismic wave groups of shallow seismic profile are well correspondent with boring geological layers.The borehole results reveal that the three reference laminas,i.e.the boundary between Malan loess and silt with clay soil at about 21m in depth,the calcareous gravel clay layer of 53.9m deep,and the calcareous silt layer of 61.9m deep,all have not depth variations at the two sides of surface steep slopes and are situated almost at the same ground surface elevations,which suggests that the steep slopes at the earth's surface should not result from the activities of Laoyachen Fault.In this study,through shallow seismic P wave and S wave exploration as well as combination of joint borehole geological sections,not only the location and characteristics of Laoyachen Fault was determined,but the geological and seismological evidences for the fault activity estimations were provided.

Determination of Regional Dip And Formation Properties From Log Data In a High Angle Well1

Abstract: An efficient method for determining regional dip angles and formation properties in high angle wells is presented. As a first step, logs are processed to detect similar features. The feature extraction process is speeded up by observing that variation in the formation properties of a high angle well is typically far less than that of a vertical well. Consequently, log data can be appropriately filtered and considerably down-sampled while preserving the essential features of the log. A wavelet-based method is used for multilevel decomposition of log data. Once similar features are recognized, tool trajectory and other information may be combined to select a few features that satisfy certain operating and geological constraints. These features, in conjunction with the logs and tool trajectory, provide an initial set of dip angles and formation parameters. Estimates of dip angles and formation parameters may be improved by an iterative procedure that minimizes the error between computed and measured logs.