Abstract Distributed Acoustic Sensing (DAS) is an emerging technology for earthquake monitoring and subsurface imaging. However, its distinct characteristics, such as unknown ground coupling high noise level, pose challenges to signal processing. Existing machine learning models optimized conventional seismic data struggle with DAS due ultra-dense spatial sampling limited manual labels. We introduce a semi-supervised approach address the phase-picking task of data. use pre-trained PhaseNet...

Earthquake focal mechanisms provide critical in-situ insights about the subsurface faulting geometry and stress state. For frequent small earthquakes (magnitude< 3.5), their are routinely determined using first-arrival polarities picked on vertical component of seismometers. Nevertheless, quality is usually limited by azimuthal coverage local seismic network. The emerging distributed acoustic sensing (DAS) technology, which can convert pre-existing telecommunication cables into arrays...

Abstract Distributed Acoustic Sensing (DAS) is a promising technique to improve the rapid detection and characterization of earthquakes. Previous DAS studies mainly focus on phase information but less amplitude information. In this study, we compile earthquake data from two arrays in California, USA, one submarine array Sanriku, Japan. We develop data‐driven method obtain first scaling relation between magnitude. Our results reveal that amplitudes recorded by different regions follow similar...

Geophysical characterization of calderas is fundamental in assessing their potential for future catastrophic volcanic eruptions. The mechanism behind the unrest Long Valley Caldera California remains highly debated, with recent periods uplift and seismicity driven either by release aqueous fluids from magma chamber or intrusion into upper crust. We use distributed acoustic sensing data recorded along a 100-kilometer fiber-optic cable traversing caldera to image its subsurface structure. Our...

Abstract Vadose zone soil moisture is often considered a pivotal intermediary water reservoir between surface and groundwater in semi-arid regions. Understanding its dynamics response to changes meteorologic forcing patterns essential enhance the climate resiliency of our ecological agricultural system. However, inability observe high-resolution vadose over large spatiotemporal scales hinders quantitative characterization. Here, utilizing pre-existing fiber-optic cables as seismic sensors,...

We describe a new method, full-waveform inversion by model extension (FWIME), that recovers accurate acoustic subsurface velocity models from seismic data when conventional methods fail. leverage the advantageous convergence properties of wave equation migration analysis (WEMVA) with accuracy and high-resolution nature (FWI) combining them into robust mathematically consistent workflow minimal need for user inputs. The novelty FWIME resides in design cost function novel optimization strategy...

Abstract The stress field perturbation caused by magmatic intrusions within volcanic systems induces strain in the surrounding region. This effect results opening and closing of microcracks vicinity intrusion, which can affect regional seismic velocities. In late November 2023, we deployed a distributed acoustic sensing interrogator to convert an existing 100‐km telecommunication fiber‐optic cable along coast Iceland's Reykjanes peninsula into dense array, has run continuously. Measuring...

Continuous geodetic measurements near volcanic systems have advanced our understanding of magma transport dynamics. However, capturing high spatio-temporal resolution dike intrusion dynamics remains challenging. In this study, we introduce fiber-optic geodesy, an approach that enabled us to track intrusions Grindav&amp;#237;k, Iceland, on a minute time scale. This utilizes low-frequency distributed acoustic sensing (LFDAS) along telecommunication fiber cable measure quasi-static signals...

Abstract Geolocalization of distributed acoustic sensing (DAS) array channels represents a crucial step whenever the technology is deployed in field. Commonly, geolocalization performed using point-wise active-source experiments, known as tap tests, conducted vicinity recording fiber. However, these controlled-source experiments are time consuming and greatly diminish ability to promptly deploy such systems, especially for large-scale DAS experiments. We present methodology instrumentation...

Producing reliable acoustic subsurface velocity models still remains the main bottleneck of oil and gas industry’s traditional imaging sequence. In complex geologic settings, output conventional ray-based or wave-equation-based tomographic methods may not be sufficiently accurate for full-waveform inversion (FWI) to converge a geologically satisfactory earth model. We create new method referred as by model extension (FWIME) in which wave-equation migration analysis (WEMVA) technique is...

A single horizontal distributed acoustic sensing (DAS) fiber is notoriously challenging for microseismic analysis even when it close to recorded events. Due its uniaxial measurement, locations suffer from circular ambiguity. Nonetheless, in unconventional plays, the presence of dispersive guided waves DAS records can partially resolve such If reservoir has lower seismic velocities than surrounding medium, act as a waveguide. In this case, are generated only by events occurring inside or...

Elastic full-waveform inversion (FWI) can provide accurate and high-resolution subsurface parameters. However, its high computational cost prevents the application of this method to large-scale field-data scenarios. To mitigate limitation, we have developed a target-oriented elastic FWI methodology based on redatuming step that relies upon an extended least-squares migration process. In our approach, surface-reflection data be attributed given portion when mapped into image space. This...

Low-velocity zones located deep in the subsurface can act as seismic waveguides. Traditionally, their experimental observation has been limited by practical challenges of situ recording. We use a measurement technique which optical fibers are turned into sensors. The fiber is deployed along horizontal well drilled inside 15-m-thin shale formation at depth about 2 km. Owing to high-resolution recording fiber, we distinctly observe three previously elusive guided wave modes over wide frequency...

Abstract The identification of preexisting near-surface faults represents a piece crucial information needed to correctly assess the seismic hazard any area. mapping these structures is particularly challenging in densely populated and heavily urbanized areas. We use ambient noise recorded by dense array Seal Beach, California, image shallow fault lines via reflected surface-wave analysis. Our results highlight presence previously unknown that correlate remarkably well with seismicity active...

Abstract Distributed Acoustic Sensing (DAS) is an emerging technology for earthquake monitoring and subsurface imaging. The recorded seismic signals by DAS have several distinct characteristics, such as unknown coupling effects, strong anthropogenic noise, ultra-dense spatial sampling. These aspects differ from conventional data networks, making it challenging to utilize at present monitoring. New analysis algorithms are needed extract useful information data, determining the first arrival...

Abstract Distributed acoustic sensing (DAS) provides dense arrays ideal for seismic tomography. However, DAS only records average axial strain change along the cable, which can complicate interpretation of surface-wave observations. With a rectangular array located in City Oxnard, California, we compare phase velocity dispersion at same location illuminated by differently oriented virtual sources. The curves are consistent colinear and noncolinear sources, suggesting that observations most...

Source to receiver distances used in seismic data acquisition have been steadily increasing and it is now common work with acquired more than 10 km of offset. Subbasalt exploration undershooting are just two applications which long-offset reflections sought. However, such often subjected muting suppress normal moveout (NMO) stretch artifacts, thus causing a loss valuable information. To retrieve these portions the recorded wavefield, we developed nonstretch NMO correction based on wavelet...

The main issue inherent to full waveform inversion (FWI) is its inability correctly recover the Earth's subsurface seismic parameters from inaccurate starting models. This behavior due presence of local minima in FWI objective function. To overcome this problem, we propose a new function which modify nonlinear modeling operator problem by adding correcting term that ensures phase matching between predicted and observed data. additional computed demigrating an extended model variable,...

We investigate the use of model reduction by interpolation for improving convergence to true solution full waveform inversion (FWI) techniques. develop a 2D spline workflow using basic (B-spline) functions that allows us represent our unknown parameters on coarser nonuniform grid. propose new FWI where all data are simultaneously inverted, but grid is gradually refined with iterations. The inverted given then used as initial guess following performed finer test proposed Marmousi model. find...

The high computational cost of elastic full-waveform inversion (FWI) limits its applicability to real exploration datasets; hence more simplistic and computationally cheaper methods are usually employed. However, these affected by strong assumptions (e.g., planar reflectors or ray approximation), which reduce their use in complex geological scenarios. We propose a target-oriented approach that alleviates the burden associated with FWI limiting process only portion subsurface where an...

Preserving the elastic amplitude behavior of recorded primary reflections is necessary to perform any amplitude-versusoffset (AVO) analysis within a prestack image space. We show how extended subsurface-offset space able preserve even when these events are acoustically migrated using reverse-timemigration (RTM) approach performed in least-squares fashion. On single interface model, we that angle-domain transformed subsurface offset closely follows theoretical Zoeppritz response at critical...

We present a simple method of preconditioning the gradient elastic multi-component full-waveform inversion (FWI) using an approximated Gauss-Newton Hessian. By sampling this matrix we are able estimate Hessian elements. use to compute preconditioner apply during inversion. show on synthetic 2D sediment model that main-diagonal approximation already improves convergence rate FWI optimization and properly scales gradients for different parameter classes. Therefore, it also decreases...