Relative Dip Research Articles

A Separately Determining Anisotropic Formation Parameter Method for Triaxial Induction Data

This letter describes a method to extract the unknown parameters of the formation using triaxial induction data based on the whole-space model. Two single-parameter coupled functions are constructed to determine the horizontal conductivity and the relative dip. After that, the vertical conductivity is solved analytically using another single-parameter function. The method is extremely fast and can be implemented for real-time processing and interpretation to allow decision making on the well site. The results can be further refined via postprocessing while the relative dip is required to be constant within an interval.

MP31-14 MICRORNAS AND GENES RELATED TO EPITHELIAL-MESENCHYMAL TRANSITION IN PROSTATE CANCER

You have accessJournal of UrologyProstate Cancer: Basic Research II1 Apr 2014MP31-14 MICRORNAS AND GENES RELATED TO EPITHELIAL-MESENCHYMAL TRANSITION IN PROSTATE CANCER Betina Katz, Sabrina Reis, Nelson Dip, Nayara Viana, Denis Morais, Caio Moura, Iran Silva, Alexandre Iscaife, Miguel Srougi, and Katia RM. Leite Betina KatzBetina Katz More articles by this author , Sabrina ReisSabrina Reis More articles by this author , Nelson DipNelson Dip More articles by this author , Nayara VianaNayara Viana More articles by this author , Denis MoraisDenis Morais More articles by this author , Caio MouraCaio Moura More articles by this author , Iran SilvaIran Silva More articles by this author , Alexandre IscaifeAlexandre Iscaife More articles by this author , Miguel SrougiMiguel Srougi More articles by this author , and Katia RM. LeiteKatia RM. Leite More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2014.02.923AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Prostate cancer (PCa) is the most common cancer in men and the second leading cause of cancer-related mortality. Although most patients present with localized disease at diagnosis, 5% already have metastatic disease. One of the main mechanisms of tumor progression is the epithelial-mesenchymal transition (EMT). In EMT, epithelial cells lose intercellular adhesion and acquire a mesenchymal phenotype with invasiveness and metastatic potential. The main event is the repression of E-cadherin by transcriptional factors, including ZEB1, ZEB2, Snail, Slug and Twist. microRNAs are also involved in EMT, and one of the most important is the miR-200 family, which induces epithelial differentiation by inhibiting ZEB. Our aim was to evaluate the expression of genes and miRNAs involved in EMT in localized PCa and to correlate with clinicopathological features and outcome after surgery. METHODS Fifty-one fresh-frozen samples from patients with localized PCa submitted to radical prostatectomy were selected. Gene expression of E-cadherin, N-cadherin, Vimentin, TGFβ, ZEB1, ZEB2, Snail, Slug, Twist and PDGF-D and miRNA expression of miRNAs 200b, 429, 141, 203, 205, 183, 373, 21, 9, 1, 495, 29b, 30a, 34a, 155 and 10b were assessed by qRT-PCR. Controls were comprised by 10 cases of benign prostatic hyperplasia. The genes and miRNAs expression were compared with Gleason score (GS), pathological stage (pT), preoperative PSA and biochemical recurrence. RESULTS The majority of cases showed overexpression of E-cadherin and Twist and underexpression of N-cadherin, Vimentin, TGFβ, ZEB1, Slug and PDGF-D. miRNAs 200b, 429, 141, 203, 205, 183, 373 and 21 were overexpressed, while miRNAs 9, 495, 29b and 1 were underexpressed. The remaining showed a variable expression pattern. There was a significant correlation between lower expression of miR 200b, 30a and 1 and non-organ-confined disease (pT3). miRNAs 200b and 30a levels were also underexpressed in cases with GS ≥ 8 comparing to GS ≤ 6 (6.94 vs 18.67, p=0.035) and in patients categorized as having high risk disease in relation to low risk (1.70 vs 6.37; p=0.03), respectively. Yet, Vimentin and Twist were significantly overexpressed in the high risk group. CONCLUSIONS Localized PCa still maintains the epithelial phenotype. However, underexpression of miRNAs 200b, 30a and 1 were significantly associated with more advanced stage and higher GS. The mesenchymal markers Vimentin and Twist were also overexpressed in patients with high risk disease. These miRNAs and genes could be used in the clinical practice as tumor markers to characterize tumor aggressiveness. © 2014FiguresReferencesRelatedDetails Volume 191Issue 4SApril 2014Page: e327 Advertisement Copyright & Permissions© 2014MetricsAuthor Information Betina Katz More articles by this author Sabrina Reis More articles by this author Nelson Dip More articles by this author Nayara Viana More articles by this author Denis Morais More articles by this author Caio Moura More articles by this author Iran Silva More articles by this author Alexandre Iscaife More articles by this author Miguel Srougi More articles by this author Katia RM. Leite More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Experimental models of transfer zones in rift systems

Transfer zones in rift basins are classified into convergent, divergent, and synthetic, based on the relative dip directions of adjacent faults within the transfer zone. Experimental models were constructed to determine the geometry, evolution, and fault patterns associated with each of these transfer zones. In addition, basement faults with initially approaching, laterally offset, and overlapping geometries were modeled. The models consisted of two layers, with stiff clay representing basement and soft clay representing the sedimentary cover. Laser scanning and three-dimensional surface modeling were used to determine the map geometry to compare the models with examples of natural structures. The experimental models showed many similarities with conceptual models but also showed more details and a few significant differences. Typically, divergent transfer zones are narrower than convergent transfer zones, for the same initial spacing between basement faults. The differences between the different initial fault configurations (approaching, laterally offset, or overlapping) are the degree of interaction of the secondary faults, the amount of overlap between the fault zones, and in some cases, the width of the transfer zone. The main faults propagate laterally and upward and curve in the direction of dip of the faults, so that the faults curve toward each other in convergent transfer zones, away from each other in divergent transfer zones, and in the same direction in synthetic transfer zones. A primary difference with schematic models is the significant component of extensional fault propagation folding (drape folding), accompanied by secondary faulting within the sedimentary cover, especially in the early stages of fault propagation. Therefore, all three types of transfer zones are characterized by significant folding and related variations in the shapes of structures. The transfer zones are marked by a progressive change in relief from the footwall to the hanging wall, resulting in a saddle-shaped geometry. The hanging walls of the faults are marked by a gentle flexure or rollover into the fault, with the amount of flexure increasing with fault throw away from the fault tip. The geometries and fault patterns of the experimental structures match some of the observations in natural structures and also provide predictive analogs for interpretation of surface and subsurface structures and the delineation of structural traps in rift basins.

Inversion-based method for interpretation of logging-while-drilling density measurements acquired in high-angle and horizontal wells

We introduce a sector-based inversion method to improve the petrophysical interpretation of logging-while-drilling density measurements acquired in high-angle and horizontal wells. The central objective is to reduce shoulder-bed effects on the measurements. This approach is possible because of a recently developed technique to accurately and efficiently simulate borehole density measurements. The inversion-based interpretation method consists of first detecting bed boundaries from short-spacing detector or bottom-quadrant compensated density by calculating their variance, representative of the measurement inflection point, within a sliding window. Subsequently, a correlation algorithm calculates dip and azimuth from the density image. Depth shifts that vary azimuthally and depend on relative dip angle, together with the effective penetration length of each sensor, refine previously selected bed boundaries. Next, the inversion method combines sector-based density measurements acquired at all measurement points along the well trajectory to estimate layer-by-layer densities. In the presence of standoff, the method excludes upper sectors most affected by standoff to reduce inaccuracies due to borehole mud. To verify the reliability and applicability of the inversion method, we first use forward simulations to generate synthetic density images for a model constructed from field data. Results indicate that inversion improves the interpretation of azimuthal density data as it consistently reduces shoulder-bed effects. Inversion results obtained from field measurements are appraised by quantifying the corresponding integrated porosity-meter yielded by inversion methods in comparison to standard techniques that use simple cutoffs on field-processed compensated density. Integrated porosity-meter of inverted synthetic density measurements increases by 4.6% with respect to noninverted field measurements. Also, integrated porosity-meter obtained from inversion results that include only bottom sectors improved by 65.4% with respect to that calculated with field-compensated, bottom-quadrant density measurements.

Crosswell electromagnetic response in a fractured medium

We experimentally verified that material-averaging techniques can be used for numerically modeling the response of the crosswell electromagnetic (crosswell EM) system in a fractured medium. We have designed a scaled model of the crosswell EM system, and verified that the laboratory data are in good agreement with the simulated response for different cases of fractures present in a host medium. Simulations of realistic scenarios in a hydrocarbon-filled reservoir indicate that the presence of fracture clusters can significantly affect the crosswell EM system response. The magnitude of the effect primarily depends on the number of fractures and their dip relative to the transmitter and receiver wells. In particular, small clusters of fractures filled with saline connate water produce large artifacts on the response, provided that the relative dip to the wells is large enough. The presence of a fracture cluster creates a characteristic signature in the full crosswell EM tomographical data set; therefore, crosswell EM data provides information related to the main fractures that are present between the wells. The inclusion of the fracture information as an additional constraint to the inversion of the crosswell EM data is expected to provide an improved interpretation of the reservoir fluids in the interwell space.

A graphical approach for slope mass rating (SMR)

Slope mass rating (SMR) is a commonly used geomechanical classification for the characterization of rock slopes. SMR is computed adding to basic rock mass rating (RMR) index, calculated by characteristic values of the rock mass, several correction factors depending of the discontinuity–slope parallelism, the discontinuity dip, the relative dip between discontinuity and slope and the employed excavation method. In this work a graphical method based on the stereographic representation of the discontinuities and the slope to obtain correction parameters of the SMR ( F 1, F 2 and F 3) is presented. This method allows the SMR correction factors to be easily obtained for a simple slope or for several practical applications as linear infrastructures slopes, open pit mining or trench excavations.

Apparent dip and apparent anisotropy from multifrequency triaxial induction measurements

The triaxial (or multicomponent) induction log is used to measure not only the resistivity anisotropy of an anisotropic formation but also the relative dip of the tool with respect to the formation. The anisotropic resistivity and the relative dip of layered formations are also inverted from the triaxial induction-log measurements at a depth by assuming a homogeneous anisotropic formation or at multiple depths by assuming a multilayered formation model. When the triaxial induction log is run at multiple frequencies, multifrequency focusing can be applied to the log measurements. Then, the apparent dip is algebraically defined from the frequency-focused triaxial induction measurements at a depth. The apparent dip yields the true dip in an anisotropic formation. The algebraically calculated apparent dip may be used to determine the effective dip in layered formations. The apparent dip yields the true dip in thinly bedded formations. The apparentdip also yields the true dip in thick anisotropic formations. However, the apparent dip yields a smaller dip than the true dip when the anisotropy is small (the anisotropy effect). It yields a much smaller dip in thick isotropic formations. Like the apparent dip, the apparent anisotropy is algebraically defined from the frequency-focused triaxial induction measurements at a depth. The apparent anisotropy yields the true anisotropy in an anisotropic formation. The algebraically calculated apparent anisotropy may be applied to layered formations. The apparent anisotropic resistivity (horizontal and vertical) can likewise be determined algebraically from the frequency-focused triaxial data. In contrast to the apparent dip, which yields the true dip in thinly bedded formations but not in thicker formations, the apparent anisotropy yields the true anisotropy in thick anisotropic formations but not in thinner anisotropic formations. The apparent anisotropy is affected by the shoulder-bed anisotropy when the formation is not thick (the shoulder-bed effect).

Relationship Between the Geometric Parameters of Rock Fractures, the Size of Percolation Clusters and REV

Modeling fractured rocks with numerical methods requires some derived parameters, among which the fracture network connectivity and the size of the representative elementary volume (REV) are both of crucial importance. Percolation and REV analyses were made by the RepSim code. The program uses input parameters such as fractal dimension of the fracture midpoints (Dc), length exponent (E) and relative dip (αr) data. For percolation analysis, the relative sizes of the largest percolation clusters have been calculated by stochastic realizations of the simulated fracture networks with different parameter triplets. Furthermore, fracture networks can be classified into three major types on the basis of their (E,Dc,αr) parameters. For the REV calculations, the porosity of the generated fracture network was calculated. The derived REV size of a fracture network depends essentially on input parameters and shows a decreasing tendency with increasing D and E and vice versa. The method mentioned above was tested on both metamorphic samples of the Pannonian Basin and Variscan granitoid rocks of the Moragy Complex. Percolation values predicted for the Moragy granite are highly sensitive to alterations in the input parameters. The amphibolite bodies displayed a modeled fracture network with 80 to 90% of all fractures being interconnected, while the largest achievable percolation cluster size of gneiss is less than 10%. The REV size of the amphibolite is about 20 m as a result of connected fractures filling the whole body, while gneiss has lower porosity and higher REV (approximately 70 m).

First-principles calculations and tight-binding molecular dynamics simulations of the palladium-hydrogen system

We present a study of palladium-hydrogen system by the linearized augmented plane-wave (LAPW) and Naval Research Laboratory (NRL) tight-binding (TB) methods. We constructed a TB Hamiltonian by fitting to first-principles LAPW data for the electronic energies of a large range of palladium and palladium hydride structures differing in symmetry and compositions as a function of volume. This TB Hamiltonian was then used to calculate phonon frequencies and elastic constants. Our calculations show good agreement with experiments and demonstrate the efficiency of the NRL-TB scheme. In addition, we performed tight-binding molecular dynamics simulations to calculate the density of states, mean-squared displacement, and the formation energy as a function of hydrogen content. We found a relative dip in the lattice energy of structures near the experimental limit of hydrogen content. We calculated the nearest hydrogen-hydrogen distance for various compositions of palladium hydride and confirmed the Switendick criterion.

Determination of Dip and Anisotropy from Multi-frequency Tri-axial Induction Measurements

The tri-axial (or multi-component) induction log is used to measure not only the resistivity anisotropy of an anisotropic formation but also the relative dip of the tool with respect to the formation. When the tri-axial induction log is run at multiple frequencies, multi-frequency focusing can be applied to the measurements. The apparent dip and the apparent anisotropy are algebraically deflned from the frequency-focused tri-axial induction measurements. The apparent dip gives the true dip in thinly bedded formations, but a smaller dip than the true dip in a thick anisotropic bed when the anisotropy is small (the anisotropy efiect). The apparent anisotropy gives the true anisotropy in thick anisotropic formations but is afiected by the shoulder bed anisotropy when the formation is not thick (the shoulder bed efiect).

Associations of ambulatory blood pressure levels with white matter hyperintensity volumes in hypertensive patients

High daytime and nighttime blood pressure (BP) levels, and apparently also an abnormal nocturnal BP dip, coincide with a greater extent of cerebral white matter hyperintensities (WMHs). We assessed the relationship between ambulatory BP and volumes of WMH, and distinguished between periventricular and deep WMH because of their supposedly different cause. A total of 210 hypertensive patients (106 men) without cardiovascular and cerebrovascular disease, with a mean age of 52.5 +/- 12.5 years, and untreated office BP levels of 170 +/- 24/104 +/- 12 mmHg underwent duplicate 24-h ambulatory blood pressure monitoring (off medication) and brain MRI to quantify the WMHs (total, periventricular, and deep) and brain volumes. We performed linear regression analyses to relate the mean 24-h, awake, and asleep BPs, and the relative nocturnal BP dip to the different volumes of WMHs, while adjusting for age, sex, brain volume, and vascular risk factors. Higher 24-h, awake, and asleep BP levels were continuously, without distinct thresholds, and independently associated with a greater volume of total (all P < 0.001), periventricular (P < 0.001), and, to a lesser extent, deep (P < 0.05) WMHs. Nocturnal BP dipping was not related to the volume of WMHs. Higher 24-h, daytime, and nighttime BP levels are independently associated with WMH volumes.

Detecting Concealed Knowledge Using a Novel Attentional Blink Paradigm

Traditional concealed information paradigms rely on the idea that stimuli that are meaningful to a person (critical items) will draw attentional resources disproportionately, relative to stimuli that are not (irrelevant items), generating detectable differences on a suitable dependent variable (behavioral, psychophysiological, or neural). Here, we introduce a behavioral paradigm that could be used to reveal concealed information by exploiting the link between concealed information and attentional processes more directly. This novel paradigm is based on the attentional blink phenomenon in which detection of a stimulus reduces detection accuracy rates of subsequent target stimuli within a 200-500 ms time window. We hypothesized that a well-known face used as a critical item could capture attentional resources automatically, making it harder to detect the occurrence of a subsequently presented target face. The results confirmed this hypothesis, and showed that concealed knowledge of a famous face could be detected in 9 out of 12 individuals by looking for a relative dip in target detection accuracy after the presentation of a critical item.

Anisotropic correction of sonic logs in wells with large relative dip

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 [Formula: see text] in siliciclastic rocks, then I show that it is straightforward to compute the anisotropy correction to both compressional and shear logs using [Formula: see text] 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.

Real-Time Image Data Aids Horizontal Drilling in Carbonate Reservoirs Onshore Abu Dhabi

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 101916, "Real-Time Image Data for Successful Horizontal Drilling in Carbonate Reservoirs Onshore Abu Dhabi, UAE," by Maria Teresa Ribeiro, Mohamed Al Neaimi, Irfan Hendrawan, Sultan Karrani, Mohamed Ben Saad, Mohammed R. Ayoub, Kamal Zubair, Khalid Al Marzouqui, and Suaad Khoori, Adco, prepared for the 2006 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 5–8 November. Real-time image interpretation was used during an intensive horizontal-well drilling campaign in two major carbonate fields onshore Abu Dhabi. Major and smaller faults were identified by use of sophisticated methods for interpreting seismic data. These faults were confirmed with image logs while drilling the horizontal field-development wells. Real-time image-data interpretation enabled geosteering decisions while drilling into reservoirs with complex structure or unknown geology or in areas with sparse geological or structural information. Introduction The success of drilling horizontal wells depends on accurate placement of the wellbore in the reservoir. Generally, placement is based on offset-well information, seismic data, and geological models. Although seismic data provide continuous coverage, the resolution is poor, and velocity errors may lead to wrong depths at planned well locations. As more wells are drilled, additional detailed measurements are acquired, including formation dip and acoustic velocity, and the reservoir geometry is refined. Dip data can be used to recognize structures such as folds and faults and to aid the interpretation of the depositional environment. Depth uncertainty related to survey measurements could lead to structural uncertain-ty, especially for highly deviated wells. The presence of unexpected subseismic faults can cause problems with correct well placement while drilling. Logging-while-drilling (LWD) real-time azimuthal resistivity and density images can be used for accurate estimation of dip and strike of the intersected formations. Structural heterogeneities, such as faults, can be detected and immediate actions taken while geosteering the well. This action is particularly important for horizontal wells in thin reservoirs, in structurally complex geology, or in an area where structure is not calibrated because of sparse control points. In such situations, the use of image data while drilling the well can help drilling of a good well in terms of well placement and accessibility. Real-Time Imaging Technology LWD technology uses the rotation of bottomhole-assembly sensors to scan around the interior surface of a borehole. Technologies to acquire images of formation gamma ray, density, photoelectric factor, and resistivity are available. The amplitude of an image sinusoid gives quantitative information on the relative dip and azimuth between the borehole and the formation layer. Most LWD images are oriented relative to the top of the borehole (generally, these images are acquired in high-angle wells). If the borehole is perpendicular to the layering, the amplitude of the sinusoid is low. With increasing relative angle, the amplitude of the sinusoid increases until the borehole is parallel to the formation and the layering appears as lines running down the image. Generally, the sinusoid magnitude on the image gives sufficient information while drilling to aid well geosteering. Measurement-while-drilling data are used to derive true formation dip and azimuth, helping update the reservoir-structure information.

A tutorial on complex seismic trace analysis

Complex seismic trace analysis treats a seismic trace as the product of two independent and separable functions: instantaneous amplitude and cosine of the instantaneous phase. At any given time, instantaneous amplitude is the maximum value the seismic trace can attain under a constant phase rotation, and instantaneous phase is the phase angle required to rotate the trace to the maximum. Defining these two attributes in this way permits complex seismic trace analysis to be founded without reference to the complex trace. All other complex seismic trace attributes derive from amplitude and phase through differentiation, averaging, combination, or transformation. The chief derived attributes are frequency, relative amplitude change, wavelength, dip, and azimuth. At any point on a seismic trace, the instantaneous attributes describe a sinusoid that locally matches the trace. Most instantaneous attributes are improved through filtering or weighted averaging. The phase wavenumber vector provides a convenient basis for quantifying 3D seismic properties such as reflection parallelism.

Improving signal to noise ratio of seismic profiles using an image processing technique

This paper introduces an image processing technique into seismic data processing as a noise attenuation technology. The image separation of the seismic profile is obtained by using grating operators based on different time dips and a set of relative single dip profiles is obtained. A high signal to noise ratio profile can be obtained during reconstruction by statistical weighting. With further processing analysis and geological study, a high signal to noise profile that can meet geological requirements can be produced. The real data examples show that the signal to noise ratio of the porfile is greatly improved, the resolution of the profile is maintained, and the fault terminations are much clearer after using the image processing method.

A 3D parametric inversion algorithm for triaxial induction data

We develop a parametric inversion algorithm to determine simultaneously the horizontal and vertical resistivities of both the formation and invasion zones, invasion radius, bed boundary upper location and thickness, and relative dip angle from electromagnetic triaxial induction logging data. This is a full 3D inverse scattering problem in transversally isotropic media. To acquire sufficient sensitivity to invert for all of these parameters, we collect the data using a multicomponent, multispacing induction array. For each transmitter-receiver spacing this multicomponent tool has sets of three orthogonal transmitter and receiver coils. At each logging point single-frequency data are collected at multiple spacings to obtain information at different depths of investigation. This inversion problem is solved iteratively with a constrained regularized Gauss-Newton minimization scheme. As documented in the literature, the main computational bottleneck when solving this full 3D inverse problem is the CPU time associated with constructing the Jacobian matrix. In this study, to achieve the inversion results within a reasonable computational time, we implement a dual grid approach wherein the Jacobian matrix is computed using a very coarse optimal grid. Furthermore, to regularize the inversion process we use the so-called multiplicative regularization technique. This technique automatically determines the regularization parameter. Synthetic data tests indicate the developed inversion algorithm is robust in extracting formation and invasion anisotropic resistivities, invasion radii, bed boundary locations, relative dip, and azimuth angle from multispacing, multicomponent induction logging data.

Determination of relative angles and anisotropic resistivity using multicomponent induction logging data

We have developed a new algorithm that retrieves information about relative dip angle, relative azimuth angle, vertical resistivity, and horizontal resistivity from multicomponent EM induction logging data. To investigate how relative dip and azimuth angles affect multicomponent induction logging data, we performed a sensitivity analysis using an anisotropic whole space model. Based upon the sensitivity analysis, we designed a two‐step procedure to recover relative dip, relative azimuth, horizontal resistivity, and vertical resistivity. In the first step, the observed data are transformed into a new data set independent of the azimuth angle; a simultaneous inversion method recovers relative dip angle, vertical resistivity, and horizontal resistivity. In the second step, a 1D line search is performed to decide relative azimuth angle. Synthetic and field data tests indicate that the new inversion algorithm can extract information about relative dip and azimuth angles as well as the anisotropic resistivity structure from multicomponent induction loggingdata.

Blood pressure in sleep disordered breathing

Aims: To investigate blood pressure (BP) in children with sleep disordered breathing (SDB). Methods: BP was measured during single night polysomnography in 23 suspected SDB child patients with adenotonsillar hypertrophy,...

Interseismic uplift and strain accumulation in Nepal Himalaya

Savage (1983, 1995) and Thatcher and Rundle (1984) have postulated elastic half space and viscoelastic coupling models of strain accumulation and earthquake occurrences at the upper surface of the subducting lithospheric plate called detachment. These models infer the presence of a locked zone on the detachment during interseismic periods. The analysis based on interseismic uplift data of about two decades in Nepal Himalaya indicates absence of the postulated locked zone and instead suggests occurrence of thrust fault type (up dip) slip on the entire detachment (Jackson and Bilham, 1994). A question then arises as to whether the strains are accumulating at all in this region. Further, if strains are accumulating we may like to investigate the process responsible. The answer is provided by a plausible model visualising strain accumulation due to differential motion of the medium particles on the detachment and those above it. This relative down dip motion of the medium particles on the detachment may be occurring even if the subducting and the overriding plates are not fully coupled or locked. Sections with high coupling on the detachment would have accumulated larger strains compared to those with low coupling. A temporal decrease in up dip slip rate on the detachment, by virtue of increase in coupling or strain hardening, further represents interseismic accumulation of shear strains. On the other hand, a temporal increase in up dip slip rate, when activates unstable motion, may culminate into occurrence of a large earthquake. This model explains the observed elevation changes in the Himalaya and corresponding inference of up dip slip on the detachment. It also provides plausible justification to the occurrence of moderate and great earthquakes on a part of the detachment lying primarily below the Lesser-Higher Himalaya.