Active Seismic Data Research Articles

A combination of waveform inversion and reverse-time modelling for microseismic event characterization in complex salt structures

The increased emission of greenhouse gases into the atmosphere, causing climate changes, leads to a strong requirement of renewable energy resources. However, they are intermittent and need buffer storage to bridge the time gap between production and public demands. The injection of gas (e.g. compressed air or hydrogen) in sealed underground structures like salt caverns is one approach to solve this problem. Possible risks related to cavern storage are gas leakages from the injection tube into the surrounding sediments, material failure in salt rock surrounding the cavern during irregular operation and in the most extreme case a partial collapse of the cavern. For the early detection of these problems, a geophysical monitoring strategy is required. The objective of this paper was to map possible leakage paths outside of the salt structures and local failures within the cavern walls by the localization of crack-induced microseismic events. Classical methods require arrival time picking and phase identification. An alternative approach is elastic reverse-time modelling (RTMOD), where the recorded microseismic events are numerically backpropagated from the receiver positions into the elastic underground model. The resulting seismic wavefield focuses at the location of the event, which can be subsequently imaged by estimating the maximum of the seismic energy at each underground point. However, the success of this approach highly depends on the used elastic background model. In case of complex salt bodies, the strong velocity contrast between the salt and the surrounding sediments is a major problem. Therefore, we propose a combined monitoring approach, consisting of a seismic full waveform inversion of active source reflection seismic data to accurately image the background velocity model and subsequent RTMOD for the microseismic event localization. Accuracy and sensitivity with respect to the acquisition geometry and random noise will be demonstrated using a complex benchmark model. Furthermore, the localization accuracy is discussed for three different scenarios covering the detection of a partial cavern collapse, a gas leakage and the occurrence of cracks within the cavern wall due to extreme loading conditions during irregular operation.

Seismic analysis of the 13 October 2012 Te Maari, New Zealand, lake breakout lahar: Insights into flow dynamics and the implications on mass flow monitoring

On 6 August 2012 an eruption of the upper Te Maari vent Tongariro volcano and subsequent debris flow in the Mangatetipua channel created a debris dam and ephemeral lake. The lake reached its maximum volume of 50,000m3 by 13 October, initiating dam breaching at 22:30 NZDT (11:30 UTC) after a period of intense rainfall. The breach eventually grew to 29×12m, causing eroded debris flow sediment and water to remobilize as a lahar. The event, comprising multiple surges, lasted ~30min, and displaced 57,000m3 of remobilized sediment up to 4.5km downstream. To determine the dynamics of the event, the seismic signals generated by the lahar were compared with active seismic source data collected in February 2013. The comparison used a common frequency band range of 3–10Hz to compute amplitude for four near-field seismic stations. For periods with signal-to-noise ratios above 2.0, we obtained lahar amplitude distributions that match best the equivalent active source amplitudes within ~0.5km of the dam breakout. The accumulated seismic energy of the lahar was estimated at 1.93×109Nm, whereas the peak energy was 6.88×107Nm. Results of this work may improve the characterization of future mass flow events in the Te Maari/Mangatetipua area through the calibration of seismic stations used in this study.

Shear wave velocity profile estimation by integrated analysis of active and passive seismic data from small aperture arrays

We present an integrated approach for deriving the 1D shear wave velocity (Vs) information at few tens to hundreds of meters down to the first strong impedance contrast in typical sedimentary environments. We use multiple small aperture seismic arrays in 1D and 2D configuration to record active and passive seismic surface wave data at two selected geotechnical sites in Germany (Horstwalde & Löbnitz). Standard methods for data processing include the Multichannel Analysis of Surface Waves (MASW) method that exploits the high frequency content in the active data and the sliding window frequency–wavenumber (f–k) as well as the spatial autocorrelation (SPAC) methods that exploit the low frequency content in passive seismic data. Applied individually, each of the passive methods might be influenced by any source directivity in the noise wavefield. The advantages of active shot data (known source location) and passive microtremor (low frequency content) recording may be combined using a correlation based approach applied to the passive data in the so called Interferometric Multichannel Analysis of Surface Waves (IMASW).In this study, we apply those methods to jointly determine and interpret the dispersion characteristics of surface waves recorded at Horstwalde and Löbnitz. The reliability of the dispersion curves is controlled by applying strict limits on the interpretable range of wavelengths in the analysis and further avoiding potentially biased phase velocity estimates from the passive f–k method by comparing to those derived from the SPatial AutoCorrelation method (SPAC). From our investigation at these two sites, the joint analysis as proposed allows mode extraction in a wide frequency range (~0.6–35Hz at Horstwalde and ~1.5–25Hz at Löbnitz) and consequently improves the Vs profile inversion.To obtain the shear wave velocity profiles, we make use of a global inversion approach based on the neighborhood algorithm to invert the interpreted branches of the dispersion curves. Within the uncertainty given by the apparent spread of forward models we find that besides a well defined sediment velocity range also a reasonable minimum estimate of bedrock depth and bedrock velocity can be achieved. The Vs estimate for the best model in Horstwalde ranges from ~190m/s at the surface up to ~390m/s in the bottom of the soft sediment column. The bedrock starts earliest around 200m depth and bedrock velocities are higher than 1000m/s. In Löbnitz, we observe slightly lower velocities for the sediments (~165–375m/s for the best model) and a minimum thickness of 75m.

Seismic imaging of a megathrust splay fault in the North Chilean subduction zone (Central Andes)

Prominent trench-parallel fault systems in the arc and fore-arc of the Chilean subduction zone can be traced for several thousand kilometers in north–south direction. These fault systems possibly crosscut the entire crust above the subduction megathrust and are expected to have a close relationship to transient processes of the subduction earthquake cycles. With the motivation to image and characterize the structural inventory and the processes that occur in the vicinity of these large-scale fault zones, we re-processed the ANCORP'96 controlled-source seismic data set to provide images of the faults at depth and to allow linking geological information at the surface to subsurface structures. The correlation of the imaging results with observed hypocenter locations around these fault systems reveals the origin and the nature of the seismicity bound to these fault systems. Active and passive seismic data together yield a picture of a megathrust splay fault beneath the Longitudinal Valley at mid-crustal level, which can be observed from the top of the subduction plate interface and which seems to be connected to the Precordilleran Fault System (PFS) known at the surface. This result supports a previously proposed tectonic model where a megathrust splay fault defines the Western Altiplano as a crustal-scale fault-bend-fold. Furthermore, we clearly imaged two branches of the Uyuni-Kenayani Fault (UKF) in a depth range between 0 and 20km. In summary, imaging of these faults is important for a profound understanding of the tectonic evaluation and characterization of the subduction zone environment, for which the results of this study provide a reliable basis.

Passive-source multitaper-spectral method based low-frequency data reconstruction for active seismic sources

Passive seismic data contain large amounts of low-frequency information. To effectively extract and compensate active seismic data that lack low frequencies, we propose a multitaper spectral reconstruction method based on multiple sinusoidal tapers and derive equations for multisource and multitrace conditions. Compared to conventional cross correlation and deconvolution reconstruction methods, the proposed method can more accurately reconstruct the relative amplitude of recordings. Multidomain iterative denoising improves the SNR of retrieved data. By analyzing the spectral characteristics of passive data before and after reconstruction, we found that the data are expressed more clearly after reconstruction and denoising. To compensate for the low-frequency information in active data using passive seismic data, we match the power spectrum, supplement it, and then smooth it in the frequency domain. Finally, we use numerical simulation to verify the proposed method and conduct prestack depth migration using data after low-frequency compensation. The proposed power-matching method adds the losing low frequency information in the active seismic data using the low-frequency information of passivesource seismic data. The imaging of compensated data gives a more detailed information of deep structures.

Seismic imaging of the shallow crust beneath the Krafla central volcano, NE Iceland

AbstractWe studied the seismic velocity structure beneath the Krafla central volcano, NE Iceland, by performing 3‐D tomographic inversions of 1453 earthquakes recorded by a temporary local seismic network between 2009 and 2012. The seismicity is concentrated primarily around the Leirhnjúkur geothermal field near the center of the Krafla caldera. To obtain robust velocity models, we incorporated active seismic data from previous surveys. The Krafla central volcano has a relatively complex velocity structure with higher P wave velocities (Vp) underneath regions of higher topographic relief and two distinct low‐Vp anomalies beneath the Leirhnjúkur geothermal field. The latter match well with two attenuating bodies inferred from S wave shadows during the Krafla rifting episode of 1974–1985. Within the Leirhnjúkur geothermalreservoir, we resolved a shallow (−0.5 to 0.5 km below sea level; bsl) region with low‐Vp/Vs values and a deeper (0.5–1.5 km bsl) high‐Vp/Vs zone. We interpret the difference in the velocity ratios of the two zones to be caused by higher rock porosities and crack densities in the shallow region and lower porosities and crack densities in the deeper region. A strong low‐Vp/Vs anomaly underlies these zones, where a superheated steam zone within felsic rock overlies rhyolitic melt.

The Reliability of Low Cost Data Logger for Active Seismic (Surface-Wave) Data Measurements

Seismic data acquisition needed a relatively fast data logger and multi channels input capability. For this purpose, we construct a measuring instruments based on low cost voltage data logger DI710ULS from DATAQ. The sensors (geophones) have 4.5 [Hz] natural frequency, produce an alternating electric voltage at rate 28 [V/m/s]. The ground shaking / velocity rate of active seismic surface-wave measurement from 5 kg hammer, at 3m distances, is less than 2 [mm/s]. This will produce an alternating voltage at less than 100 [mV].The active seismic surface wave measurements need around 1 ms time sampling for every channels and this instruments can record 7200 data for 8 differential channels, which is sufficient for this purpose. The DI710ULS has a standalone capability and all digital data were recorded in SDcard, whose very light and compact for field acquisition. By only 14[bit] DAC, the data shows reliable and seems good enough by 12.2 [μV] sampling. The data collected by using this data logger were successfully processed for surface wave analysis, and giving a reasonable result.

Modified surface boundary conditions for elastic waveform inversion of low-frequency wide-angle active land seismic data

Modified surface boundary conditions for elastic waveform inversion of low-frequency wide-angle active land seismic data

Joint analysis of Rayleigh-wave dispersion and HVSR of lunar seismic data from the Apollo 14 and 16 sites

Active and passive seismic data from the Apollo 14 and 16 missions are analyzed with the aim of determining robust shear-wave velocity (VS) profiles of the uppermost lunar strata.While data from the Active Seismic Experiment (ASE) allow the study of Rayleigh-wave dispersion by means of Multiple Filter Analysis (MFA), data acquired by the Passive Seismic Experiment (PSE) are used to determine the Horizontal-to-Vertical Spectral Ratio (HVSR). These two datasets are jointly analyzed according to state-of-the-art procedures in order to overcome the intrinsic limitations of both methodologies (when considered independently) and with the aim of determining a solution (i.e., the vertical VS profile) not affected by non-uniqueness of the solution and not based on any a priori assumption.Obtained results appear in general agreement with the early P-wave refraction analyses (a sharp contact between a very soft Regolith and a stiffer overlain layer is apparent) and indicate very low shear-wave velocities and very high Q values (low dissipation) also confirmed by a number of seismological studies on moonquakes and meteoroid impacts.

Ambient noise to estimate depth to basement: case studies from East Africa basins

Passive recording of background noise have been successfully used to retrieve information about the large-scale structure of a sedimentary basin. Ambient noise can be used to retrieve velocity profiles in order to investigate the velocity structure and the depth of a sedimentary basin, in an unexplored area and/or when additional constraints on the basement depth may be needed for interpretation of active seismic or non-seismic data. We exploit techniques usually used in geotechnical or earthquake hazard/engineering studies. Surface wave dispersion analysis can be used to obtain 1D velocity-depth profiles below an array of seismic stations which record passive ambient noise. Analogously, the horizontal-to-vertical spectral ratio of both the surface and body waves can provide 1D velocity-depth profiles below standalone seismic stations which record passively ambient noise. We successfully applied this technique in Uganda, Ethiopia and Kenya, where field surveys were carried out to recover the depth to basement. With this work we present and discuss the results we obtained in those areas, the accuracy of which was validated by comparing with depth values obtained by other seismic and non-seismic datasets (independently acquired and processed).

An integrated geophysical imaging of the upper-crustal features in the Harney Basin, southeast Oregon

The Harney Basin is a relatively flat-lying depression in the northeast corner of the enigmatic High Lava Plains volcanic province in eastern Oregon. A thick blanket of volcanics including flood basalts, rhyolites, tuffs, ash flows, and distinct eruptive centers covers the basin, making it very difficult to study the upper-crustal features. In addition to a portion of the High Lava Plains active source seismic data in the Harney Basin area, we employed geologic, gravity, magnetic, digital elevation, and other geospatial data in our integrated study. We generated an upper-crustal 3D seismic tomographic model of the Harney Basin using a sparse grid of 2D seismic lines and constructed an integrated geophysical model of the upper-crustal structure, which reveals that the basin reaches as deep as 6 km in its central area. The tomographic inversion also detected some unusually high-velocity (>6.5 km/s) bodies in the upper crust near the central basin area. The presence of several ash-flow tuffs and voluminous rhyolites in the Harney Basin region indicates that the sources of these materials are nearby. We observe two major caldera-shaped features within the basin, which we interpret to be likely candidates for the source of some of these tuffs. These potential calderas are associated with low seismic velocities, low gravity anomaly values, and topographic depressions. We interpret the extent and evolution of these potential calderas based on our integrated analysis.

Late Mesozoic magmatic plumbing system in the onshore–offshore area of Hong Kong: Insight from 3-D active-source seismic tomography

We used active source wide-angle seismic data to determine a high-resolution P-wave crustal tomography beneath the onshore–offshore area of Hong Kong at the southern end of a broad belt dominated by the late Mesozoic intrusive and extrusive rocks in the coastal region of Southeast China. The active source data are much more precise than the natural earthquake data and so can be used to study the fine crustal structure. Our results reveal a localized high-velocity anomaly in the lower crust offshore between Hong Kong and Dangan Island, which may reflect basaltic underplating that is closely associated with formation of voluminous silicic eruptions and granitoid plutons in the onshore–offshore area of Hong Kong. Tilted high-velocity zones connecting with the localized high-velocity anomaly in the lower crust are clearly visible in the entire crust beneath Dangan Island and the calderas of Hong Kong. Taking into account the previous geochemical, petrologic and numerical modeling results, we think that the tilted high-velocity zones may be the results of mingling of mafic and felsic end members and extreme degree of crustal partial melt extraction necessary to generate a large amount of extrusive rocks in the calderas, reflecting cooled magma conduits as a manifestation of solidified Late Mesozoic magmatic plumbing system in the crust. Considering the petrologic and geochemical characteristics of the late Mesozoic granites and basalt in Southeast China, we suggest that subduction and dehydration of the paleo-Pacific plate might trigger the basaltic magma underplating and result in extensive crust–mantle interaction, which not only provided necessary heat energy to cause the crustal partial melting, but also added minor mafic materials to the newly generated granitic melts. This model explains our tomographic results as well as the intimate mingling of coeval mafic and silicic magmas in Hong Kong. Intersecting faults could play an important role in forming magma conduits and loci of fissure-like volcanic centers.

Advanced geophysical underground coal gasification monitoring

Underground Coal Gasification (UCG) produces less surface impact, atmospheric pollutants and greenhouse gas than traditional surface mining and combustion. Therefore, it may be useful in mitigating global change caused by anthropogenic activities. Careful monitoring of the UCG process is essential in minimizing environmental impact. Here we first summarize monitoring methods that have been used in previous UCG field trials. We then discuss in more detail a number of promising advanced geophysical techniques. These methods – seismic, electromagnetic, and remote sensing techniques – may provide improved and cost-effective ways to image both the subsurface cavity growth and surface subsidence effects. Active and passive seismic data have the promise to monitor the burn front, cavity growth, and observe cavity collapse events. Electrical resistance tomography (ERT) produces near real time tomographic images autonomously, monitors the burn front and images the cavity using low-cost sensors, typically running within boreholes. Interferometric synthetic aperture radar (InSAR) is a remote sensing technique that has the capability to monitor surface subsidence over the wide area of a commercial-scale UCG operation at a low cost. It may be possible to infer cavity geometry from InSAR (or other surface topography) data using geomechanical modeling. The expected signals from these monitoring methods are described along with interpretive modeling for typical UCG cavities. They are illustrated using field results from UCG trials and other relevant subsurface operations.

High resolution seismic data coupled to Multibeam bathymetry of Stromboli island collected in the frame of the Stromboli geophysical experiment: implications with the marine geophysics and volcanology of the Aeolian Arc volcanic complex (Sicily, Southern Tyrrhenian sea, Italy).

New high resolution seismic data (Subbottom Chirp) coupled to high resolution Multibeam bathymetry collected in the frame of the Stromboli geophysical experiment aimed at recording active seismic data and tomography of the Stromboli Island are here presented. The Stromboli geophysical experiment has been already carried out based on onshore and offshore data acquisition in order to investigate the deep structure and the location of the magma chambers of the Stromboli volcano. A new detailed swath bathymetry of Stromboli Island is here shown and discussed to reconstruct an up-to-date morpho-bathymetry and marine geology of the area compared to the volcanologic setting of the Aeolian Arc volcanic complex. Due to its high resolution the new Digital Terrain Model of the Stromboli Island gives interesting information about the submerged structure of the volcano, particularly about the volcano-tectonic and gravitational processes involving the submarine flanks of the edifice. Several seismic units have been identified based on the geologic interpretation of Subbottom Chirp profiles recorded around the volcanic edifice and interpreted as volcanic acoustic basement pertaining to the volcano and overlying slide chaotic bodies emplaced during its complex volcano-tectonic evolution. They are related to the eruptive activity of Stromboli, mainly poliphasic and to regional geological processes involving the intriguing geology of the Aeolian Arc, a volcanic area still in activity and needing improved research interest.

Active seismic sources as a proxy for seismic surface processes: An example from the 2012 Tongariro volcanic eruptions, New Zealand

The 6 August 2012 eruption from Tongariro volcano's Te Maari vent comprised a complex sequence of events including at least 4 eruption pulses, a large chasm collapse, and a debris avalanche (volume of ~7×105m3) that propagated ~2km beyond the eruptive vent. The eruption was poorly observed, being obscured by night time darkness, and the eruption timing must be unravelled instead from a complex seismic record that includes discrete volcanic earthquakes, a sequence of low to moderate level spasmodic tremor and an intense burst of seismic and infrasound activity that marked the eruption onset. We have discriminated the evolution of the complex surface activity by comparing active seismic source data to the seismic sequence in a new cross correlation source location approach. We dropped 11 high impact masses from helicopter to generate a range of active seismic sources in the vicinity of the eruption vent, chasm, and debris avalanche areas. We obtained 8 successful drops having an impact energy ranging from 3 to 9×106Nm producing observable seismic signals to a distance of 5 to 10km and having good signal to noise characteristics in the 3–12Hz range. For the 8 drops, we picked first-P arrival times and calculated amplitude spectra for a uniform set of four stations. We then compared these proxy source excitations to the natural eruption and pre-eruption data using a moving window cross correlation approach. From the correlation processing, we obtain a best matched source position in the near vent region for the eruption period and significant down channel excitations during both the pre and post eruption periods. The total seismic energy release calculated from the new method is ~8×1011Nm, similar to an independently estimated calculation based on the radiated seismic energy. The new energy estimate may be more robust than those calculated from standard seismic radiation equations, which may include uncertainties about the path and site effects. The active source data carry this information directly in the waveforms, yielding a simple conversion between seismic amplitude and energy.

Passive Seismic Ambient Noise Correlation: An Example from the Ketzin Experimental CO2 Storage Site, Germany

Passive seismic ambient noise correlation is potentially a new tool to monitor carbon dioxide storage sites. Unlike conventional monitoring tools, such as time-lapse active seismic surveys, the passive seismic ambient noise correlation method is a relatively low cost method and can be performed together with microseismic and reservoir monitoring. In this study, we test the method at the Ketzin CO2 storage site, Germany. A new passive seismic survey was performed in August 2013 together with an active survey in conjunction with a source test. The survey consisted of two profiles, Line 1 and Line 2. Line 1 contained 42 10Hz geophones spaced at 24 m intervals and Line 2 contained 23 DSU3 (3-component MEMS) sensors spaced at 5 m intervals. In total, 6 nights and 3 daytime series of ambient noise data were recorded. First, we applied autocorrelation to the passive data records to reconstruct the reflection response. The results show good structural correlation with a stacked section from the active data. Then we used passive seismic interferometry to reconstruct common shot gathers for each receiver location. Surface waves were observed in some retrieved gathers from Line 1. However, for Line 2 we also observed refracted and reflected waves in some retrieved shot gathers. Here we review ambient noise correlation methods and compare our results with active seismic data.

Four Years of Experience with a Permanent Seismic Monitoring Array at the Ketzin CO2 Storage Pilot Site

CO2 was injected into a saline aquifer near the town of Ketzin in Germany from July 2008 to August 2013. To monitor CO2- migration close to the injection well, TNO installed a fixed 2D seismic array of 120 meters length in 2009, with 3- component (3- C) geophones at the surface, 4-component receivers at 50 meters depth and a central vertical array of 4-component receivers. The test-bed is used both for the recording of high-quality active time-lapse seismic data as well as for continuous passive seismic data recording. Here we focus on the latest results obtained from active source experiments, micro-seismic data analysis and ambient noise seismic interferometry (ANSI) of passive seismic data. Data from two experiments with a source driven by linear motors (permanent) and an impact hammer source (semipermanent) were evaluated in order to assess the repeatability of the two source types.The repeatability of the first source was relatively high compared to the second source. After the stop of injection in August 2013, active seismic shots were acquired repeatedly on a daily basis. These data did not show significant impedance changes at reservoir level. Microseismic event analysis of passive seismic data detected a few local events originating from reservoir depth. In order to quantify these events the seismic array was successfully calibrated by using independent earthquake recording. This yielded estimates of the local magnitude for local events within the range [-2.5,0.5]. Recent work on ANSI focused on the application of this method on both synthetic and field data. The resulting reflection response shows a strong resemblance with outcomes from active shot reflection profiles, and the key reflectors at reservoir level have comparable characteristics

Seismic exploration‐scale velocities and structure from ambient seismic noise (>1 Hz)

The successful surface waves retrieval in solid‐Earth seismology using long‐time correlations and subsequent tomographic images of the crust have sparked interest in extraction of subsurface information from noise in the exploration seismology. Subsurface information in exploration seismology is usually derived from body‐wave reflections > 1 Hz, which is challenging for utilization of ambient noise. We use 11 h of noise recorded in the Sirte basin, Libya. First, we study the characteristics of the noise. We show that the bulk of the noise is composed of surface waves at frequencies below 6 Hz. Some noise panels contain nearly vertically traveling events. We further characterize these events using a beamforming algorithm. From the beamforming, we conclude that these events represent body‐wave arrivals with a fairly rich azimuthal distribution. Having body‐wave arrivals in the noise is a prerequisite for body‐wave reflections retrieval. We crosscorrelate and sum the recorded ambient‐noise panels to retrieve common‐source gathers, following two approaches—using all the noise and using only noise panels containing body‐wave arrivals likely to contribute to the reflections retrieval. Comparing the retrieved gathers with active seismic data, we show that the two‐way traveltimes at short offsets of several retrieved events coincide with those of reflections in the active data and thus correspond to apexes of reflections. We then compare retrieved stacked sections of the subsurface from both approaches with the active‐data stacked section and show that the reflectors are consistent along a line. The results from the second approach exhibit the reflectors better.

Geophysics news in brief

As our News in Brief series takes a look at emerging research, examining alternately different areas and topics in the earth sciences, various experts will be invited to provide a brief look around the recent significant work conducted in their area. The selection of research papers is left up to each expert and due to the broadness of each field is not intended to be a comprehensive overview. Links to the published work are provided in each section. In this issue we’ve invited Stefan Buske, Professor of Exploration Geophysics at the technical university, TU Bergakademie Freiberg, in Germany, to select some of the latest findings in seismology. His working group focuses on the development and application of seismic imaging, inversion and modelling techniques for active and passive-source seismic data. In this third article of our series, Buske outlines the recent significant developments, studying the large-scale oscillations of the Earth and the natural and induced earthquakes, as well as the methodological advances in the remote detection of large landslides and in the reconstruction of the subsurface.

Structural Characteristics of the Basement beneath Qiangtang Basin in Qinghai‐Tibet Plateau: Results of Interaction Interpretation from Seismic Reflection/Refraction Data

Abstract:The studies on configuration, character/property of the basement of Qiangtang basin is helpful for evaluating petroleum and nature gas resources as well as understanding the basin evolvement. Recently a moderate to high‐grade metamorphic gneiss rock was found underlying beneath very low metamorphic Ordovician strata in Mayer Kangri to the north of the central uplift. That fact actually proved existence of the crystalline basement just the distribution and structures of pre‐Paleozoic crystalline basement still remain puzzle. In recent years a number of active sources deep seismic profiling, to aim at lithospheric structure of northern Tibet and petroleum resources of the Qiangtang basin, had been conducted that make it possible to image the structure of the basement of the Qiangtang. Near vertical reflection profiles, included those acquired previously and those during 2004 to 2008, have been utilized in this study. By through the interaction process and interpretation between the reflection profiles and the wide‐angle profile, a model with the detailed structure and velocity distribution from surface to the depth of 20 km of Qiangtang basin has been imaged. Based on the results and discussions of this study, the preliminary conclusions are as follows: (1) The velocity structure section (∼20 km) that is interactively constrained by the refraction and reflection seismic data reveals that the sedimentary stratum gently lie until 10 km in the south Qiangtang basin. (2) The basement consists of fold basement (the upper) and crystalline basement (the lower). The fold basement buried at the average depth of 6 km with a velocity of 5.2–5.8 km/s. The shallowest appear at range of the central uplift. The crystalline basement is underlying beneath the fold basement at the average depth of 10 km with a velocity of 5.9–6.0 km/s except near Bangong‐Nujiang suture. (3) The high‐velocity body at the depth range of 3–6 km of the central uplift is considered as a fragment of the crystalline basement that perhaps was raised by Thermal or deformation. (4) The lower‐consolidated fold basement show more affinity of Yangtze block but the crystalline basement seems more approximate to Lhasa terrene in geophysical nature. We have attempted to improve the resolution and reliability by interaction of the active seismic data and prove it effective to image complex basement structure. It will be a potential to process the piggy‐back acquisition data and has wide prospects.