Seismic Interferometry Method Research Articles

Investigating small-strain site response using inverse soil dynamic parameters from downhole arrays

Previous research on site response has primarily focused on reproducing and predicting ground motions recorded by vertical seismic arrays. This study evaluated the ability to reproduce and predict small-strain site response at the Treasure Island Downhole Array and Delaney Park Downhole Array using inverse soil dynamic parameters. First, parameters such as seismic wave velocity profiles and Rayleigh damping ratios were obtained through seismic interferometry and spectral ratio methods based on the earthquake records. Subsequently, the validity and reliability of these inverse soil dynamic parameters were evaluated by comparing the simulated and observed ground responses. Finally, the inverse method was compared with other methods considering spatial variability in one-dimensional site response analysis. Quantitative comparisons show that the inverse method effectively predicts and reproduces site response and outperforms the traditional method relying on the single borehole shear wave velocity profile and damping ratio from empirical model. Moreover, the inverse method better captures spatial variability at the Delaney Park Downhole Array.

Estimation of seismometer clock time offsets using Kalman Filter towards accurate seismic velocity change

SUMMARY Monitoring seismic velocity changes obtained from ambient noise correlations is widely used to understand changes in rock properties in response to earthquakes, volcanic activities and environmental changes. Since continuous seismic data have been accumulated, this method can estimate long-term changes in seismic velocity, such as crustal recovery after a major earthquake and temporal variations in seismic velocity related to long-term environmental change. Changes in seismic velocity can be estimated with a high temporal resolution by measuring the phase differences of ambient noise correlations based on a seismic interferometry method. Still, these phase differences are influenced not only by seismic wave velocity changes but also by errors in clock timing in seismometers. The clock drift occurs due to out-of-synchronization with the GPS clock and the drift of the internal clock. Therefore, to accurately monitor temporal changes in crustal structure by measuring the phase differences of noise correlations, it is crucial to evaluate the contribution of errors in clock timing to the phase differences. Recently, a method using an extended Kalman filter based on a state-space model was developed for reliable detection of temporal changes in the waveforms of ambient noise correlations, with the state-space model offering the advantage of flexible modelling of time-series data. In this study, we incorporated the time-shifts caused by clock time errors of the seismometer into the state-space model of the temporal changes in ambient noise correlations. We estimated seismic velocity changes, amplitude changes of noise correlations and clock time errors from 2010 April to 2021 September at seismic stations around the Shinmoe-dake volcano in Japan, which experienced eruptions in 2011 and 2018, respectively. Several stations exhibited clear clock time offsets, and the occurrence of clock time-shifts coincided with the dates when the data logger was turned off for seismic station maintenance or replacement of the seismometer. The proposed method provides stable estimations with respect to the signal-to-noise ratio of the waveform, and this stable estimation facilitates accurate timing of seismic recordings, enabling precise analysis of seismic phase arrival times.

Research on improved cross-correlation seismic interferometry method based on marine vertical cable seismic data

Research on improved cross-correlation seismic interferometry method based on marine vertical cable seismic data

Subsurface Imaging Using Interferometry of Distributed Acoustic Sensing Ambient Noise Measurement along a Dark Fiber Line: A Case Study in Downtown Reno, Nevada

ABSTRACT Distributed acoustic sensing (DAS) technology is an emerging field of seismic sensing that enables recording ambient noise seismic data along the entire length of a fiber-optic cable at meter-scale resolution. Such a dense spatial resolution of recordings over long distances has not been possible using traditional methods because of limited hardware resources and logistical concerns in an urban environment. The low spatial resolution of traditional passive seismic acquisition techniques has limited the accuracy of the previously generated velocity profiles in many important urban regions, including the Reno-area basin, to the top 100 m of the underlying subsurface. Applying the method of seismic interferometry to ambient noise strain rate data obtained from a dark-fiber cable allows for generating noise cross correlations, which can be used to infer shallow and deep subsurface properties and basin geometry. We gathered DAS ambient noise seismic data for this study using a 12 km portion of a dark-fiber line in Reno, Nevada. We used gathered data to generate and invert dispersion curves to estimate the near-surface shear-wave velocity structure. Comparing the generated velocity profiles with previous regional studies shows good agreement in determining the average depth to bedrock and velocity variations in the analyzed domain. A synthetic experiment is also performed to verify the proposed framework further and better understand the effect of the infrastructural cover along the cable. The results obtained from this research provide insight into the application of DAS using dark-fiber lines in subsurface characterization in urban environments. It also discusses the potential effects of the conduit that covers such permanent fiber installations on the produced inversion results.

Anisotropic seismic velocity variations in response to different orientations of tidal deformations

SUMMARY Microcracks or micropores in rocks cause the elastic moduli to change with the applied strain owing to the nonlinear elasticity of the geomaterial, which causes temporal changes in the seismic wave velocity. Thus, variations in seismic wave velocity can be used as a proxy for understanding the strain or stress variations in the crust, which are crucial for figuring out the dynamics of the fault zones and volcanic domains. According to the theory of nonlinear elasticity, the second- and third-order elastic constants and strain tensors contribute to the strain derivative of seismic wave velocity changes. Although laboratory experiments have estimated third-order elastic constants for rock samples, the in situ values of those constants for the crust are difficult to obtain. In this study, seismic velocity changes were investigated in different directions of tidal deformations to provide constraints on the third-order elastic constants in the shallow crust by applying a seismic interferometry method to ambient noise records. We observed that negative velocity changes were of larger magnitude in the station-pair direction parallel to the tidal strain’s direction. Nonlinear elasticity in shallow crust may cause anisotropic velocity variations in response to tidal deformations. Our results highlight the use of velocity change measurements in different directions of tidal strain to constrain nonlinear elastic parameters on a field scale.

Spatiotemporal evaluation of Rayleigh surface wave estimated from roadside dark fiber DAS array and traffic noise

Seismic imaging and monitoring of the near-surface structure are crucial for the sustainable development of urban areas. However, standard seismic surveys based on cabled or autonomous geophone arrays are expensive and hard to adapt to noisy metropolitan environments. Distributed acoustic sensing (DAS) with pre-existing telecom fiber optic cables, together with seismic ambient noise interferometry, have the potential to fulfill this gap. However, a detailed noise wavefield characterization is needed before retrievingcoherent waves from chaotic noise sources. We analyze local seismic ambient noise by tracking five-month changes in signal-to-noise ratio (SNR) of Rayleigh surface wave estimated from traffic noise recorded by DAS along the straight university campus busy road. We apply the seismic interferometry method to the 800 m long part of the Penn State Fiber-Optic For Environment Sensing (FORESEE) array. We evaluate the 160 virtual shot gathers (VSGs) by determining the SNR using the slant-stack technique. We observe strong SNR variations in time and space. We notice higher SNR for virtual source points close to road obstacles. The spatial noise distribution confirms that noise energy focuses mainly on bumps and utility holes. We also see the destructive impact of precipitation, pedestrian traffic, and traffic along main intersections on VSGs. A similar processing workflow can be applied to various straight roadside fiber optic arrays in metropolitan areas.

Near-surface characterization using distributed acoustic sensing in an urban area: Granada, Spain

SUMMARY The Granada Basin in southeast Spain is an area of moderate seismicity. Yet, it hosts some of the highest seismic hazards in the Iberian Peninsula due to the presence of shallow soft sediments amplifying local ground motion. In urban areas, seismic measurements often suffer from sparse instrumentation. An enticing alternative to conventional seismometers is the distributed acoustic sensing (DAS) technology that can convert fibre-optic telecommunication cables into dense arrays of seismic sensors. In this study, we perform a shallow structure analysis using the ambient seismic field interferometry method. We conduct a DAS array field test in the city of Granada on the 26 and 27 August 2020, using a telecommunication fibre. In addition to the existing limitations of using DAS with unknown fibre-ground coupling conditions, the complex geometry of the fibre and limited data recording duration further challenge the extraction of surface-wave information from the ambient seismic field in such an urban environment. Therefore, we develop a processing scheme that incorporates a frequency–wavenumber (f−k) filter to enhance the quality of the virtual shot gathers and related multimode dispersion images. We are able to use this data set to generate several shear-wave velocity (VS) profiles for different sections of the cable. The shallow VS structure shows a good agreement with different geological conditions of soil deposits. This study demonstrates that DAS could provide insights into soil characterization and seismic microzonation in urban areas. In addition, the results contribute to a better understanding of local site response to ground motion.

Utilization of ambient noise seismic interferometry to retrieve P‐wave reflections at Soma coal basin, Western Turkey

AbstractFollowing ambient noise seismic interferometry principles, we retrieved virtual zero‐offset vertical seismic profile shot gather using continuous seismic records obtained simultaneously during an active‐source data acquisition study from Soma coal basin, Western Turkey. We treated the data to include pure ambient noise by eliminating earthquakes, surface sweeps and quarry explosions due to mining activities. We have implemented a series of data processing steps, including spectral normalization and filtering to increase the signal‐to‐noise ratio. We produced a zero‐offset virtual shot gather by cross‐correlation and cross‐coherence methods in a coal basin for the first time and we observed the P‐wave first arrivals and reflections from the deepest coal layer (km2). Our results demonstrate that the ambient noise seismic interferometry method can serve as an alternative approach for seismic imaging and monitoring in areas where the use of active seismic sources is limited due to field conditions, provided that there are sufficient and appropriate noise sources at the wellhead.

Geological ahead-prospecting method while TBM drilling using improved seismic interferometry method: A case

Tunnel Boring Machines (TBMs) are widely applied in tunnel construction due to their advantages of fast drilling, good cave shape, safety, and economics. To guarantee the safety of TBM, it is necessary to understand the geological conditions ahead of the tunnel face. Seismic ahead-prospecting is an important method for predicting adverse geologies while TBM drilling. Seismic interferometry is the core to achieving the utilization of TBM drilling noise and dynamic detection. To better retrieve wavefield from TBM drilling noise, improved seismic interferometry based- seismic ahead-prospecting method was proposed in this paper. Firstly, the typical methods of cross-correlation, deconvolution, and cross-coherence are analyzed and selected cross-coherence for wavefield retrieval due to its advantages of less noise/artifacts and better stability. Then, the improved seismic interferometry is proposed by combining the smoothing constraint base on cross-coherence and singular spectral decomposition. Numerical simulations prove that more clear and accurate reflected waves can be retrieved by the improved method. And the improved method has been used in the Gaoligongshan tunnel and successfully detected two fractured zones ahead, supporting the safety of TBM drilling.

Tidal Response of Seismic Wave Velocity at Shallow Crust in Japan

AbstractMicrocracks in geomaterials cause variations in the elastic moduli under applied strain, thereby creating seismic wave velocity variations. These are crucial for understanding the dynamic processes of the crust, such as fault‐zone damage, healing, and volcanic activities. Solid earth tides have been used to detect seismic velocity changes responding to crustal‐scale deformations. However, no prior research has explored the characteristics of the seismic velocity variations caused by large‐scale tidal deformation. To systematically evaluate the tidal response to velocity variations, we developed a new method that utilized the flexibility of a state‐space model. The tidal response was derived from hourly stacked noise autocorrelations using a seismic interferometry method throughout Japan. In particular, large tide‐induced seismic velocity changes were observed in the low S‐wave velocity region of the shallow crust. Overall, the tidal responses of velocity variations can provide new insights into the response mechanisms of the shallow crust to applied strain.

Seismic Interferometry Method Based on Hierarchical Frequency Fusion and Its Application in Microtremor Survey

Site velocity structure determination and stratigraphic division are important purposes of microtremor survey, and the precision of dispersion curves is an important factor affecting the accuracy of microtremor survey. In order to obtain more accurate dispersion curve and S-wave velocity structure, this paper proposed a dispersion curve processing method based on hierarchical frequency fusion of seismic interferometry. Analysis was performed on the link between station pair spacing and frequency component of the collected microtremor signal dependability and exploration depth. A mathematical model of station distances and reliable frequencies of the dispersion curves were achieved through a hierarchical relationship between station distances. Then, a fusion criterion was proposed to determine the fusion boundary based on the reliable frequency, and the dispersion curves of station pairs with different distances were fused to obtain the final dispersion curve. Finally, a more accurate velocity structure was obtained through s-wave velocity conversion from shallow layers to deep ones. The method was applied to the microtremor survey of the proposed high-rise building site in Xiamen. The rectangular observation array was arranged, and the dispersion curves were extracted and processed using hierarchical frequency fusion and traditional superimposed averaging method, and the S-wave velocity and stratigraphic structure were obtained. The experimental results show that the S-wave velocity and stratigraphic structure obtained using the hierarchical frequency fusion method are in better agreement with the borehole results than the superimposed averaging method, which shows its effectiveness and application prospect.

Comparisons between non-interferometric and interferometric passive surface wave imaging methods—towards linear receiver array

SUMMARYPassive seismic methods in highly populated urban areas have gained much attention from the geophysics and civil engineering communities. Linear arrays are usually deployed for passive surface wave investigations because of their high convenience, and passive surface wave imaging methods commonly used for linear arrays can be grouped as non-interferometric methods (e.g. passive multichannel analysis of surface wave, refraction microtremor) and interferometric methods (e.g. multichannel analysis of passive surface waves and spatial autocorrelation). It is well known that the seismic interferometry method is able to retrieve Green’s function between inter-station pairs based on passive seismic data and that is how interferometric methods work. Although non-interferometric methods are also popular and effective in near-surface seismic imaging, particularly in the geotechnical industry, there is no theoretical proof to clarify the accuracy and/or the bias of these methods. In this study, we use numerical derivations and simulations to demonstrate the underlying physics for both non-interferometric and interferometric methods, under two common noise source environments including a homogeneous source distribution and a dominant in-line source distribution. We also prove the strength of interferometric methods for accurate dispersion imaging over the non-interferometric methods, and provide a way to estimate the biases in non-interferometric measurements. Finally, we present comprehensive comparisons between different passive surface wave methods with three typical field examples considering various observation systems.

Effects of high-speed train traffic characteristics on seismic interferometry

SUMMARY Train traffic has been recognized as a powerful noise source for subsurface imaging and monitoring due to its properties of being strong, economic and repeatable. Compared with the traditional train, the high-speed train (HST) runs faster and generates vibrations that also manifest as periodical signals but with a more striking feature of sharp equidistant spectral lines in the frequency spectrum. Like the vibrations generated by the traditional train, the HST-induced vibrations can be utilized after the retrieval of interstation impulse responses using seismic interferometry. However, little attention has been paid to the characteristics of HST-induced vibrations during seismic interferometry. The aim of this study is to investigate the effects of train traffic characteristics on the seismic interferometry method. We first present an alternative derivation of seismic interferometry that is not based on the assumption of uncorrelation between sources at different locations. The derivation is valid for scalar waves in 3-D and for elastic surface waves. After analysing the effects of several HST-related factors, including HST moving direction, HST carriage number, rail structure, HST speed and the stacking number of HST records, on the seismic interferometry, we find that the seismic interferometry using HST traffic noise generates crosstalk that can be effectively attenuated by stacking the interferometric results of several HSTs with slightly different speeds. This finding has been validated by the seismic interferometry of both synthetic and field HST traffic noise. We further demonstrate that the retrieved surface waves can be used to estimate near-surface velocities.

Correlation-Based Interferometry Method to Enhance Near-Surface Reflection Signals in Surface Active Seismic Exploration

In surface active seismic exploration, the near-surface imaging based on reflection signals provides valuable information for mineral exploration and deeper resources. However, the strong noises at near surface and stretching effects at nonzero offsets with conventional seismic data processing method severely damage the seismic reflection signals with low fold at near surface. The innovative method for the enhancement of seismic signals is the seismic interferometry method. However, due to the one-sided illumination, the seismic interferometry is still not suitable for the retrieval of reflection signals in most practical situations. In this article, we present the correlation-based interferometry (CI) method to enhance the reflection signals for near-surface imaging using the first cross correlation to construct virtual reflection signals and the second cross correlation to achieve the interferometric normal move-out (INMO) correction of the seismic reflection events with no stretching, which keeps the high resolution of near-surface reflection signals. Meanwhile, because of constructive interference stack, the CI method can significantly improve the signal-to-noise ratio (SNR) of reflection signals. The synthetic and field seismic data examples illustrate that the data-driven CI method performs better than the conventional stack (CS) method based on the velocity model for the near-surface reflection imaging.

Study on real-time correction of site amplification factor

Abstract. The site amplification factor was usually considered to be scalar values, such as amplification of peak ground acceleration or peak ground velocity, or increments of seismic intensity in the earthquake early warning (EEW) system or seismic-intensity repaid report system. This paper focuses on evaluating an infinite impulse recursive filter method that could produce frequency-dependent site amplification and compare the performance of the scalar-value method with the infinite impulse recursive filter method. A large number of strong motion data of IBRH10 and IBRH19 of the Kiban Kyoshin network (KiK-net) triggered in more than 1000 earthquakes from 2004 to 2012 were selected carefully and used to obtain the relative site amplification ratio; we model the relative site amplification factor with a casual filter. Then we make a simulation from the borehole to the surface and also simulate from the front-detection station to the far-field station. Compared to different simulation cases, it can easily be found that this method could produce different amplification factors for different earthquakes and could reflect the frequency-dependent nature of site amplification. Through these simulations between two stations, we can find that the frequency-dependent correction for site amplification shows better performance than the amplification factor relative to velocity (ARV) method and station correction method. It also shows better performance than the average level and the highest level of the Japan Meteorological Agency (JMA) earthquake early warning system in ground motion prediction. Some cases in which simulation did not work very well were also found; possible reasons and problems were analyzed and addressed. This method pays attention to the amplitude and ignores the phase characteristics; this problem may be improved by the seismic-interferometry method. Frequency-dependent correction for site amplification in the time domain highly improves the accuracy of predicting ground motion in real time.

Interrogating a Surging Glacier With Seismic Interferometry

AbstractSeismic interferometry can be spectacularly sensitive to temporal changes within the Earth. Zhan (2019, https://doi.org/10.1029/2019GL082411) analyzed 12 years of data from seismic stations situated near Bering Glacier, Alaska, that spanned a 2008–2011 surge. Interferometrically isolated glacier‐crossing surface waves revealed an anisotropic seismic wave speed decrease during the surge. 1‐D and 3‐D modeling suggests pressurized englacial water flow being stored and guided by a network of basal crevasses, thereby sustaining high water pressure at the bed and supporting the high surge velocities. This result is demonstrative of the potential for seismic interferometry and other cryoseismological methods to continuously monitor and reveal changes within dynamic glacial‐hydrological systems.

Drill bit noise imaging without pilot trace, a near-surface interferometry example

Abstract. Acoustic energy emitted by drill bits can be recorded by geophones on the surface and processed for an image of the subsurface using seismic interferometry methods. Pilot sensors record bit signals on the drill rig and play an important role in processing geophone traces for the image. When pilot traces are not available, traces of the nearest geophone to the rig may be used in deconvolution and cross-correlation of data, but extra signal processing efforts are required to reduce the effect of source signature on cross-correlation results. In this study, we use the seismic interferometry method to image the shallow subsurface beneath a 2-D geophone array by converting geophones to virtual sources. As there is no pilot signal available for this survey, we use the nearest geophone trace for pilot cross-correlation and pilot deconvolution. We modify the spectrum of pilot cross-correlation and deconvolution results so that the effect of source function on virtual data is minimized. We then migrate the virtual shots and compare the results of interferometric imaging with the available image from 3-D (active source) survey and assess the efficiency of our approach. We show that drill bit noise data can be used to generate a reasonably accurate image of the subsurface even in the absence of pilot recordings, but the results should be checked for the appearance of virtual multiples and depth inconsistencies that are caused by errors in the migration velocity.

Crosscoherence-based interferometry for the retrieval of first arrivals and subsequent tomographic imaging of differential weathering

Exhumation of crust exposes rocks to weathering agents that weaken the rocks’ mechanical strength. Weakened rocks will have lower seismic velocity than intact rocks and can therefore be mapped using seismic methods. However, if the rocks are heavily weathered, they will attenuate controlled-source seismic waves to such a degree that the recorded wavefield would become dominated by ambient noise and/or surface waves. Therefore, we have examined the structure of differential weathering by first-break traveltime tomography over a seismic profile extending approximately 3.5 km and acquired at a mining site in Zambia using explosive sources and a source based on the swept-impact seismic technique (SIST). Seismic interferometry has been tested for the retrieval of supervirtual first arrivals masked by uncorrelated noise. However, use of crosscorrelation in the retrieval process makes the method vulnerable to changes in the source signal (explosives and SIST). Thus, we have developed a crosscoherence-based seismic-interferometry method to tackle this shortcoming. We investigate the method’s efficiency in retrieving first arrivals and, simultaneously, correctly handling variations in the source signal. Our results illustrate the superiority of the crosscoherence- over crosscorrelation-based method for retrieval of the first arrivals, especially in alleviating spurious ringyness and in terms of the signal-to-noise ratio. These benefits are observable in the greater penetration depth and the improved resolution of the tomography sections. The tomographic images indicate isolated bodies of higher velocities, which may be interpreted as fresh rocks embedded into a heavily weathered regolith, providing a conspicuous example of differential weathering. Our study advances the potential of seismic methods for providing better images of the near surface (the critical zone).

Green’s function retrieval with Marchenko and inter-source seismic interferometry method for drill-bit seismic while drilling

Various researchers have shown that the decomposed wave-field can obtain a more accurate Green's function with seismic interferometry (SI). In the deviated and horizontal wells, traditional methods based on the difference of apparent velocity in the vertical well fail to separate downhole drill-bit source wave-field into up- and downgoing components because of the similar moveout. In recent years, one-way Green's function retrieval with the Marchenko method has been successfully applied to borehole data. Inspired by a data processing method that utilizes surface and borehole data to separate the wave-field, we have recently developed a wave-field decomposition scheme that only uses the surface recordings. The advantage of this method is that it does not need the knowledge of media properties, which is completely data-driven. Then we use the decomposed wave-field to retrieve the reflection response around the well with inter-source SI methods. The numerical experimental results show that the Marchenko method can accurately separate the wave-field. Simultaneously, the response retrieved by inter-source SI is close to the target area, and the influence of the irrelevant formation is removed.

The application of seismic interferometry for estimating a 1D S-wave velocity model with the use of mining induced seismicity

Abstract The main objective of this paper is to present the usefulness of the seismic interferometry method to determine the S-wave velocity model of the rock mass affected by exploitation in the KGHM Rudna copper ore mine. The research aim was achieved on the basis of seismic data, acquired from seismograms, of 10 strong seismic events of magnitude greater than 2.6. They were recorded by a pair of seismometers deployed on mining terrain. In the first stage, the Rayleigh wave between seismometers was estimated. Then, the group velocity dispersion curves of fundamental and first higher modes were identified. Finally, inversion of the dispersion curves to a 1D S-wave velocity model up to 500 m in depth was obtained. The velocity model was determined for the part of the rock mass partially affected by mining. The results confirm similar rock mass structure and velocities of the subsurface layers as those obtained by the archival 3D model. In both models, a high degree of correlation in the boundary location between the overburden of the Cenozoic formations and the bedrock of the Triassic formations was observed. The applied methodology can be used to estimate the S-wave velocity model in other mining regions characterized by strong seismicity.