Frequency Attenuation Research Articles

High-Precision Spectral Decomposition Method Based on VMD/CWT/FWEO for Hydrocarbon Detection in Tight Sandstone Gas Reservoirs

Seismic time-frequency analysis methods can be used for hydrocarbon detection because of the phenomena of energy and abnormal attenuation of frequency when the seismic waves travel across reservoirs. A high-resolution method based on variational mode decomposition (VMD), continuous-wavelet transform (CWT) and frequency-weighted energy operator (FWEO) is proposed for hydrocarbon detection in tight sandstone gas reservoirs. VMD can decompose seismic signals into a set of intrinsic mode functions (IMF) in the frequency domain. In order to avoid meaningful frequency loss, the CWT method is used to obtain the time-frequency spectra of the selected IMFs. The energy separation algorithm based on FWEO can improve the resolution of time-frequency spectra and highlight abnormal energy, which is applied to track the instantaneous energy in the time-frequency spectra. The difference between the high-frequency section and low-frequency section acquired by applying the proposed method is utilized to detect hydrocarbons. Applications using the model and field data further demonstrate that the proposed method can effectively detect hydrocarbons in tight sandstone reservoirs, with good anti-noise performance. The newly-proposed method can be used as an analysis tool to detect hydrocarbons.

Photoconductive and electro-optic effects in (Cd,Mg)Te single crystals measured in an experiment-on-chip configuration

We present our studies on both photoconductive (PC) and electro-optic (EO) responses of (Cd,Mg)Te single crystals. In an In-doped Cd0.92Mg0.08Te single crystal, subpicosecond electrical pulses were optically generated via a PC effect, coupled into a transmission line, and, subsequently, detected using an internal EO sampling scheme, all in the same (Cd,Mg)Te material. For photo-excitation and EO sampling, we used femtosecond optical pulses generated by the same Ti:sapphire laser with the wavelengths of 410 and 820 nm, respectively. The shortest transmission line distance between the optical excitation and EO sampling points was 75 μm. By measuring the transient waveforms at different distances from the excitation point, we calculated the transmission-line complex propagation factor, as well as the THz frequency attenuation factor and the propagation velocity, all of which allowed us to reconstruct the electromagnetic transient generated directly at the excitation point, showing that the original PC transient was subpicosecond in duration with a fall time of ∼500 fs. Finally, the measured EO retardation, together with the amount of the electric-field penetration, allowed us to determine the magnitude of the internal EO effect in our (Cd,Mg)Te crystal. The obtained THz-frequency EO coefficient was equal to 0.4 pm/V, which is at the lower end among the values reported for CdTe-based ternaries, apparently, due to the disorientation of the tested crystal that resulted in the non-optimal EO measurement condition.

Design of sEMG-detecting circuit for EMG-Bridge.

A surface electromyography (sEMG) signal typically results from the electrical activities of many muscle fibers, and can be utilized as a signal source in prostheses due to its abundance of movement information. This paper proposes an sEMG-detection circuit for the acquisition of the controlling signal in EMG-Bridge (EMGB) systems. The detection circuit mainly comprises a preamplifier, a driven right leg (DRL) circuit, a high-pass filter (HPF), a low-pass filter (LPF), and a gain adjustable amplifying circuit. The common-mode rejection ratio (CMRR) of the circuit is higher than 120 dB, the input impedance is greater than 100 MΩ, the passband range is 20~450 Hz, and the frequency attenuation in stopband is not less than 120dB/dec.

A Three-Winding Common Mode Inductor

Electronic products consist of parasitic capacitance between the circuit components and the ground, which introduces common mode (CM) noise. A CM inductor is used to block the noise following into the power supply affecting the others. However, the CM inductor and the parasitic capacitance could create resonance phenomenon that affect the filter performance in low frequency. In this paper, we investigate into this resonance phenomenon by giving a detailed analysis of the CM inductor and filter configuration. A three-winding CM inductor is then proposed to solve the aforementioned problem. This three-winding CM inductor consists of two traditional CM inductor winding and an auxiliary winding connecting to a negative impedance converter. The impedance of the CM inductor is virtually boosted up. Without physically increasing the value of the inductance, the noise attenuation in low frequency is improved and the resonance phenomenon is significantly mitigated. A prototype is constructed and practically tested on a 100-W switched-mode power supply. Experimental results show that the three-winding CM inductor operates as theoretically anticipated. The noise level at the resonant frequency is reduced by 21 dB, whereas the power consumption of the additional circuit only consumes 0.5 W.

Crustal intrinsic and scattering attenuation of high‐frequency shear waves in the contiguous United States

AbstractWe use 10 years of data of the USArray project to estimate the areal distribution of crustal intrinsic and scattering attenuation of shear waves for frequencies between 1 Hz and 20 Hz in the contiguous United States. Additionally, we report energy site amplification factors and estimate moment magnitudes for small earthquakes (M 1.5 to M 3.5). The Qopen method is used to invert for intrinsic and scattering attenuation for each event and nearby stations. Observations are collected for around 25,000 events, averaged at each station and interpolated between station locations. In a second inversion, energy site amplifications and moment magnitudes are corrected by assuming that site amplifications for one station and frequency are the same for different earthquakes. We observe a west‐east decline of intrinsic attenuation for high frequencies which reflects the west‐east transition from young, hot to old and cold crust. Scattering attenuation for high frequencies is stronger in the east with an extraordinary high attenuation around the southern part of the Appalachian Highlands and the Interior Low Plateaus. Results at low frequencies do not show clear trends. A large site amplification is observed at high frequencies in parts of the eastern United States. Estimated moment magnitudes show a good agreement to moment magnitudes independently derived from moment tensor inversion. Moment magnitudes in the west are higher than in the east for the same Richter magnitudes.

A seismic reflection from isotropic‐fractured fluid‐saturated layer

ABSTRACTAverage elastic properties of a fluid‐saturated fractured rock are discussed in association with the extremely slow and dispersive Krauklis wave propagation within individual fractures. The presence of the Krauklis wave increases P‐wave velocity dispersion and attenuation with decreasing frequency. Different laws (exponential, power, fractal, and gamma laws) of distribution of the fracture length within the rock show more velocity dispersion and attenuation of the P‐wave for greater fracture density, particularly at low seismic frequencies. The results exhibit a remarkable difference in the P‐wave reflection coefficient for frequency and angular dependency from the fractured layer in comparison with the homogeneous layer. The biggest variation in behaviour of the reflection coefficient versus incident angle is observed at low seismic frequencies. The proposed approach and results of calculations allow an interpretation of abnormal velocity dispersion, high attenuation, and special behaviour of reflection coefficients versus frequency and angle of incidence as the indicators of fractures.

Multi-Rate Adaptive Equalizer for Transmission Over Up to 50-m SI-POF

This letter presents a novel adaptive continuous-time equalizer integrated in a receiver front-end for short-reach high-speed optical communications through low-cost step-index plastic optical fibers (SI-POF). The proposed equalizer is able to compensate the variations in the frequency response and attenuation of a 1-mm diameter SI-POF but it is also able to work at different data rates ranging from 400 Mb/s to 2.5 Gb/s. The prototype has been integrated in a cost-effective standard 0.18- $\mu \text{m}$ CMOS technology, and requires 60 mW of power consumption under just 1-V supply voltage.

Effect of magnetic field on wave propagation in cylindrical poroelastic bone with cavity

In this paper, the wave propagation in an infinite poroelastic cylindrical bone with cavity is studied. An exact closed form solution is presented by employing an analytical procedure. The frequency equation for poroelastic bone is obtained when the boundaries are stress free and is examined numerically. The magnitude of the frequency equation, wave velocity and attenuation coefficient are calculated for poroelastic bone for different values of magnetic field, density and frequency. In wet bone little frequency dispersion was observed, in contrast to the results of earlier studies. Such a model would in particular be useful in large-scale parametric studies of bone mechanical response. Comparison was made with the results obtained in the presence and absence of magnetic field. The results indicate that the effect of magnetic field, density and frequency on wave propagation in poroelastic bone are very pronounced.

Seismic wave attenuation in the lithosphere of the North Tanzanian divergence zone (East African rift system)

The seismic effective quality factor (QC) and its frequently dependences or the frequency parameter (n) and attenuation coefficient (δ) for the Earth’s crust and upper mantle of the North Tanzanian divergence zone (East African rift system) were estimated from an analysis of the earthquake coda waves recorded in the SEISMO-TANZ’07 French-Tanzanian seismic experiment. The QC values increase and the n and δ values decrease with increasing frequency and length of the lapse time window. This behavior of the attenuation parameters may be evidence that the degree of heterogeneity of the lithosphere decreases with depth. Comparison of the depth variations in the attenuation coefficient δ and the frequency parameter n with the velocity structure of the region shows that there is a distinct change in the behavior of seismic wave attenuation at velocity discontinuities. The obtained attenuation parameters were compared with the same parameters obtained in our previous studies for other continental rift systems—the Baikal rift system (Eurasia) and the Basin and Range Province (North America).

Time course of changes in heart rate and blood pressure variability in rats with myocardial infarction

Our aim was to determine the time course of changes in autonomic balance in the acute (1 and 3 days), sub-acute (7 days) and chronic (28 days) phases of myocardial infarction (MI) in rats. Autonomic balance was assessed by temporal and spectral analyses of blood pressure variability (BPV) and heart rate variability (HRV). Pulsatile blood pressure (BP) recordings (30 min) were obtained in awake and unrestrained male Wistar rats (N = 77; 8-10 weeks old) with MI (coronary ligature) or sham operation (SO). Data are reported as means±SE. The high frequency (HF) component (n.u.) of HRV was significantly lower in MI-1- (P<0.01) and MI-3-day rats (P<0.05) than in their time-control groups (SO-1=68±4 vs MI-1=35.3±4.3; SO-3=71±5.8 vs MI-3=45.2±3.8), without differences thereafter (SO-7=69.2±4.8 vs MI-7=56±5.8; SO-28=73±4 vs MI-28=66±6.6). A sharp reduction (P<0.05) of BPV (mmHg2) was observed in the first week after MI (SO-1=8.55±0.80; SO-3=9.11±1.08; SO-7=7.92±1.10 vs MI-1=5.63±0.73; MI-3=5.93±0.30; MI-7=5.30±0.25). Normal BPV, however, was observed 4 weeks after MI (SO-28=8.60±0.66 vs MI-28=8.43±0.56 mmHg2; P>0.05). This reduction was mainly due to attenuation of the low frequency (LF) band of BPV in absolute and normalized units (SO-1=39.3±7%; SO-3=55±4.5%; SO-7=46.8±4.5%; SO-28=45.7±5%; MI-1=13±3.5%; MI-3=35±4.7%; MI-7=25±2.8%; MI-28=21.4±2.8%). The results suggest that the reduction in HRV was associated with decrease of the HF component of HRV suggesting recovery of the vagal control of heartbeats along the post-infarction healing period. The depression of BPV was more dependent on the attenuation of the LF component, which is linked to the baroreflex modulation of the autonomic balance.

Research on Impedance Model of Intelligent Drill String Based on the Average Transformation Theory

Cable transmission has its intrinsic advantages and it is the development tendency of intelligent drilling among all kinds of signal transmission. According to the structure characteristics of the intelligent drill string, this paper analyzes the transmission line distribution parameters of intelligent drill string combined with average transmission theory; transfer matrixes of single drill pipe, drill pipe joint and that of cascaded transmission line between them are all calculated by the transmission line transfer function; impedance model of intelligent drill string communication channel model are built according to that transfer matrix based on the two-port network, then this model is simulated by experiment and the result is analyzed; curve of error rate is got and the influence of different signal-noise ratio, different transmission rate and different transmission distance on signal transmission performance are analyzed. This model simplifies the calculation, and the frequency characteristics and attenuation characteristics of transmission line are obtained under the analog signal and the digital signal, then the average transmission signal characteristics of intelligent drill string is analyzed by intuitive squiggle. Maybe this paper could provide some theoretical guidance for intelligent drill string.

Study on infrasonic characteristics of coal samples in failure process under uniaxial loading

To study the precursory failure infrasonic characteristics of coal samples, coal rock stress loading system and infrasonic wave acquisition system were adopted, and infrasonic tests in uniaxial loading process were made for the coal samples in the studied area. Wavelet filtering, fast Fourier transform, and relative infrasonic energy methods were used to analyze the characteristics of the infrasonic waves in the loading process, including time domain characteristics, and relative energy. The analysis results demonstrated that the frequencies of the infrasonic signals in the loading process mainly distribute within 5–10 Hz, which are significantly different from noise signals. The changes of the infrasonic signals show clear periodic characters in time domain. Meanwhile, the relative energy changes of the infrasonic wave also show periodic characters, which are divided into two stages by the yield limit of coal samples, and are clear and easy to be recognized, so that they can be used as the precursory characteristics for recognizing coal sample failures. Moreover, the infrasonic waves generated by coal samples have low frequency and low attenuation, which can be collected without coupling and transmitted in long distance. This study provides an important support for the further in-situ prediction of coal rock failures.

Estimating fluid-induced stress change from observed deformation

Author(s): Vasco, DW; Harness, P; Pride, S; Hoversten, M | Abstract: Observed deformation is sensitive to a changing stress field within the Earth. However, there are several impediments to a direct inversion of geodetic measurements for changes in stress. Estimating six independent components of stress change from a smaller number of displacement or strain components is inherently non-unique. The reliance upon surface measurements leads to a loss of resolution, due to the attenuation of higher spatial frequencies in the displacement field with distance from a source.We adopt a technique suited to the estimation of stress changes due to the injection and/or withdrawal of fluids at depth. In this approach the surface displacement data provides an estimate of the volume change responsible for the deformation, rather than stress changes themselves. The inversion for volume change is constrained by the fluid fluxes into and out of the reservoir. The distribution of volume change is used to calculate the displacements in the region above the reservoir. Estimates of stress change follow from differentiating the displacement field in conjunction with a geomechanical model of the overburden. We apply the technique to Interferometric Synthetic Aperture Radar (InSAR) observations gathered over a petroleum reservoir in the San Joaquin Valley of California. An analysis of the InSAR range changes reveals that the stress field in the overburden varies rapidly both in space and in time. The inferred stress variations are found to be compatible with the documented failure of a well in the field.

Calculation method of prestack FAGVO and its applications

Frequency attenuation occurs when seismic waves propagate through the porous reservoirs containing hydrocarbons. Current researches on the seismic frequency attenuation mainly focus on the post-stack domain instead of the prestack domain. Here we propose the frequency attenuation gradient vs. offset (FAGVO) based on the amplitude variation with offset and frequency attenuation integral equations. We derive the FAGVO equation that equals to zero in a full-elastic medium and is negative in a viscoelastic medium. FAGVO is affected by the viscosity of the medium, the coefficients of reflection, the frequency variation, and high-frequency attenuation. FAGVO uses the differences of partially stacked data to decrease the interference caused by subsurface strata affecting the frequency attenuation, highlights the frequency attenuation gradient anomalies in hydrocarbon-bearing reservoir pores, and finally realizes the hydrocarbon fluid identification. The method was verified using a two-dimensional wave equation forward model and was found to be cost effective. Furthermore, the method does not require well information, which can be applied in the stage of seismic exploration, especially, in the exploration of a none-well project.

Analysis of spatiotemporal fidelity in quantitative 3D first-pass perfusion cardiovascular magnetic resonance

BackgroundWhole-heart first-pass perfusion cardiovascular magnetic resonance (CMR) relies on highly accelerated image acquisition. The influence of undersampling on myocardial blood flow (MBF) quantification has not been systematically investigated yet. In the present work, the effect of spatiotemporal scan acceleration on image reconstruction accuracy and MBF error was studied using a numerical phantom and validated in-vivo.MethodsUp to 10-fold scan acceleration using k-t PCA and k-t SPARSE-SENSE was simulated using the MRXCAT CMR numerical phantom framework. Image reconstruction results were compared to ground truth data in the k-f domain by means of modulation transfer function (MTF) analysis. In the x-t domain, errors pertaining to specific features of signal intensity-time curves and MBF values derived using Fermi model deconvolution were analysed. In-vivo first-pass CMR data were acquired in ten healthy volunteers using a dual-sequence approach assessing the arterial input function (AIF) and myocardial enhancement. 10x accelerated 3D k-t PCA and k-t SPARSE-SENSE were compared and related to non-accelerated 2D reference images.ResultsMTF analysis revealed good recovery of data upon k-t PCA reconstruction at 10x undersampling with some attenuation of higher temporal frequencies. For 10x k-t SPARSE-SENSE the MTF was found to decrease to zero at high spatial frequencies for all temporal frequencies indicating a loss in spatial resolution. Signal intensity-time curve errors were most prominent in AIFs from 10x k-t PCA, thereby emphasizing the need for separate AIF acquisition using a dual-sequence approach. These findings were confirmed by MBF estimation based on AIFs from fully sampled and undersampled simulations. Average in-vivo MBF estimates were in good agreement between both accelerated and the fully sampled methods. Intra-volunteer MBF variation for fully sampled 2D scans was lower compared to 10x k-t PCA and k-t SPARSE-SENSE data.ConclusionQuantification of highly undersampled 3D first-pass perfusion CMR yields accurate MBF estimates provided the AIF is obtained using fully sampled or moderately undersampled scans as part of a dual-sequence approach. However, relative to fully sampled 2D perfusion imaging, intra-volunteer variation is increased using 3D approaches prompting for further developments.

Back to basics on broadband seismic amplitudes, phase and resolution

Marine broadband seismic results typically have observed amplitude spectra that are inconsistent with the earth reflectivity spectra measured from spatially coincident well data. The most notable inconsistency is a visual bias towards stronger ultra-low frequency amplitudes in the 0–10 Hz range on seismic data. Whilst useful in principle for more accurate elastic seismic inversion with less dependence upon low frequency model (LFM) building and for more stable full waveform inversion (FWI), the low frequency bias will degrade seismic resolution if not balanced properly during processing. Furthermore, the observed seismic amplitude spectra on pre-stack data vary with increasing offset and the phase can strongly vary in a frequency-dependent manner. These variations are attributed to three first-order processes: 1. Progressive attenuation of higher frequencies with longer travel paths, 2. NMO stretch, and 3. Offset-dependent tuning, and may easily be compounded by inappropriate parameterization of various processing and imaging steps. A key component of elastic seismic inversion is the extraction and scaling of several angle-dependent and depth-dependent wavelets. These wavelets are ideally independent of the aforementioned processes but inevitably they are not, and the angle ranges used in the inversion impact the significance of NMO stretch and offset-dependent tuning. Even if these various considerations can all be accommodated during processing, the resolution of seismic images is limited by the resolution of the velocity model, the scattering assumptions of the imaging algorithms used, and the a priori information used to constrain imaging and inversion. After reviewing the principles of seismic wavefield propagation in the contemporary context of broadband seismic methods, largely pursued with the ambition of removing sea surface-related ghost effects, I discuss the additional uncertainties introduced into seismic signal processing by broader bandwidth data — notably at the low frequency end. I consider two rather different ‘broadband seismic’ perspectives: 1. The industry must progress towards higher fidelity and resource-consuming measurements of every source event and every receiver measurement in order to effectively deconvolve the ‘system response’ from the data, or, 2. High-end imaging solutions can automatically eliminate the ‘source term’ without requiring detailed source information — assuming that wavefield separation has robustly accounted for dynamic variations in receiver geometry. A longer term consideration of imaging suggests that the classical sequential processing paradigm is in fact dead, that the definition of ‘noise’ is changing, and that advances in hardware are enabling solutions to long-standing challenges with cross-talk artifacts and irregular illumination. The addition of appropriate a priori information into joint migration and inversion allows historical assumptions about the unknown velocity model having a smooth background to be dismissed, and step changes in velocity model resolution may be achievable. I conclude by discussing how higher resolution velocity models will translate to less non-physical efforts in processing that can corrupt pre-stack amplitude, pre-stack phase and (elastic) image resolution.

Improvement of point spread function (PSF) using linear- quadratic aperture

Since each of the modulated linear and quadratic apertures give better resolution as compared with that obtained in case of circular aperture. Hence, we believe that a combination of both linear and quadratic multilayer concentric circular aperture will give further improvement in resolution and contrast. Consequently, the following two models are assumed. The 1st aperture model is composed of successive quadratic, linear, and constant circular transmission segments from the center. In this model, the central quadratic distributed segment from the aperture is chosen in order to attenuate the low spatial frequencies. The 2nd aperture model is composed of four concentric segments. In this aperture, starting from the center, the 1st segment is dark central disk followed by a higher order, ρ 6, distribution, the next is linear, and the last has constant transmission segment. In this model, further spatial frequency attenuation is attained by the selection of the central dark disk followed by the ρ 6 distribution.The point spread function (PSF) of the described apertures is computed and compared with the corresponding annular and circular apertures. In addition, the coherent transfer function of the confocal microscope is computed using the two models of multilayer arrangement. The effect of the pinhole diameter upon the PSF of a standard CSLM using the two models of apertures is discussed. A MATLAB code is organized to perform all the numerical computations and plots.

A Frequency-Shift Method to Measure Shear-Wave Attenuation in Soft Tissues.

In vivo quantification of shear-wave attenuation in soft tissues may help to better understand human tissue rheology and lead to new diagnostic strategies. Attenuation is difficult to measure in acoustic radiation force elastography because the shear-wave amplitude decreases due to a combination of diffraction and viscous attenuation. Diffraction correction requires assuming a cylindrical wavefront and an isotropic propagation medium, which may not be the case in some applications. In this paper, the frequency-shift method, used in ultrasound imaging and seismology, was adapted for shear-wave attenuation measurement in elastography. This method is not sensitive to diffraction effects. For a linear frequency dependence of the attenuation, a closed-form relation was obtained between the decrease in the peak frequency of the gamma-distributed wave amplitude spectrum and the attenuation coefficient of the propagation medium. The proposed method was tested against a plane-wave reference method in homogeneous agar-gelatin phantoms with 0%, 10%, and 20% oil concentrations, and hence different attenuations of 0.117, 0.202, and 0.292 [Formula: see text]/Hz, respectively. Applicability to biological tissues was demonstrated with two ex vivo porcine liver samples (0.79 and 1.35 [Formula: see text]/Hz) and an in vivo human muscle, measured along (0.43 [Formula: see text]/Hz) and across (1.77 [Formula: see text]/Hz) the tissue fibers. In all cases, the data supported the assumptions of a gamma-distributed spectrum for the source and linear frequency attenuation for the tissue. This method provides tissue attenuation, which is relevant diagnostic information to model viscosity, in addition to shear-wave velocity used to assess elasticity. Data processing is simple and could be performed automatically in real time for clinical applications.

Electrically Conductive Photopatternable Silver Paste for High-Frequency Ring Resonator and Band-Pass Filter

In conventional thick-film technology, there are often problems associated with poor edges, rough surfaces, and reproducibility due to process limitations, especially for high-frequency applications. These difficulties can be circumvented by using thin-film technology, but process cost and complexity remain major concerns. In this context, photopatternable thick-film technology can offer a viable alternative due to its Newtonian rheology, which can facilitate formation of the required sharp edges. We present herein a unique attempt to formulate a photopatternable silver paste with organic (photosensitive polymer) to inorganic (silver and glass) ratio of 30:70, developed in-house by us for fabrication of thick-film-based ring resonator and band-pass filter components. The ring resonator and band-pass component structures were realized by exposing screen-printed film to ultraviolet light at wavelength of 315 nm to 400 nm for 30 s to crosslink the photosensitive polymer. The pattern was subsequently developed using 1% sodium carbonate aqueous solution. For comparison, conventional silver and silver-palladium thick films were produced using in-house formulations. The surface topology and microstructural features were examined by stereomicroscopy and scanning electron microscopy. The smoothness and edge definition of the film were assessed by profilometry. The resistivity of the samples was observed and remained in the range from 3.4 μΩ cm to 3.6 μΩ cm. The electrical properties were compared by measuring the insertion loss characteristics. The results revealed that the ring resonator fabricated using the photopatternable silver paste exhibited better high-frequency properties compared with components based on conventional silver or silver-palladium paste, especially in terms of the resonant frequency of 10.1 GHz (versus 10 GHz designed) with bandwidth of 80 MHz. Additionally, the band-pass filter fabricated using the photopatternable silver paste displayed better center frequency (f0 = 10.588 GHz) and comparable ripple and attenuation bandwidth performance on par with Cu thin film.

Frequency and lapse time dependent seismic attenuation in eastern Himalaya and southern Tibet

We have studied the attenuation characteristics of eastern Himalaya and southern Tibet by using local earthquake data set that consists of 123 well-located events, recorded by the Himalayan Nepal Tibet Seismic Experiment operated during 2001–2003. We have used single backscattering model to calculate frequency-dependent values of coda Q ( $$Q_\mathrm{c}$$ ). The estimation of $$Q_\mathrm{c}$$ is made at central frequencies 2, 4, 8 and 12 Hz through five lapse time windows from 10 to 50 s starting at double the travel time of the S-wave. The observed $$Q_\mathrm{c}$$ is found to be strongly frequency-dependent and follows a similar trend as observed in other tectonically active parts of the Himalaya. The trend of variation of $$Q_\mathrm{c}$$ with lapse time and the corresponding apparent depths is also studied. Increase in $$Q_\mathrm{c}$$ values with the lapse time suggests that the deeper part of the study region is less heterogeneous than the shallower part. The observed values of $$Q_0$$ ( $$Q_\mathrm{c}$$ at 1 Hz) and frequency parameter n indicate that the medium beneath the study area is highly heterogeneous and tectonically very active. A regionalization of the estimated $$Q_0$$ is carried out, and a contour map is prepared for the whole region. Some segments of Lesser Himalaya and Sub-Himalaya exhibit very low $$Q_0$$ , while the whole Tethyan Himalaya and some parts of Greater Himalaya are characterized by low $$Q_0$$ values. Our results are comparable with those obtained from tectonically active regions in the world.