A5017491790- Seismic Waves and Analysis
- Seismic Imaging and Inversion Techniques
- Seismology and Earthquake Studies
- Geophysics and Sensor Technology
- Advanced Fiber Optic Sensors
- High-pressure geophysics and materials
- Acoustic Wave Phenomena Research
- Underwater Acoustics Research
- Structural Health Monitoring Techniques
- Earthquake Detection and Analysis
- earthquake and tectonic studies
- Noise Effects and Management
- Speech and Audio Processing
- Geophysical Methods and Applications
- Seismic Performance and Analysis
- Drilling and Well Engineering
- Public Relations and Crisis Communication
- Ultrasonics and Acoustic Wave Propagation
- Astro and Planetary Science
- Hydraulic Fracturing and Reservoir Analysis
- Colorectal Cancer Screening and Detection
- Advanced Fiber Laser Technologies
- Diverticular Disease and Complications
- Geological Modeling and Analysis
- Methane Hydrates and Related Phenomena
Australian National University
2024
ETH Zurich
2019-2024
Wallops Flight Facility
2022-2024
École Polytechnique Fédérale de Lausanne
2022
California Institute of Technology
2015-2020
Royal United Hospital
2012
Abstract Surface waves from earthquakes are known to cause strong damage, especially for larger structures such as skyscrapers and bridges. However, common practice in characterizing seismic hazard at a specific site considers the effect of near‐surface geology on only vertically propagating body waves. Here we show that surface have unique different frequency‐dependent response geologic structure this amplification can be analytically calculated manner similar current practices. Applying...
Abstract Background Cannabidiol (CBD) and cannabidiolic acid (CBDA) are reported to have antinociceptive, immunomodulatory anti‐inflammatory actions. Objectives To determine if CBD/CBDA is an effective therapy for canine atopic dermatitis (cAD). Animals Thirty‐two privately owned dogs with cAD. Materials methods Prospective, randomised, double‐blinded, placebo‐controlled study. Concurrent therapies were allowed remained unchanged. Dogs randomly assigned receive either 2 mg/kg of equal mix (n...
Abstract For accurate seismic hazard evaluation, both the spatial and frequency‐dependent variabilities in amplitudes of earthquake ground motions are needed. While this information is rarely fully available due to paucity relevant data, dense arrays like 5200‐geophone array Long Beach, California provide opportunity study amplitude variability. Here we show that ambient noise correlation from Beach can be used directly determine site amplification factors. We analyze Rayleigh‐wavefield...
Abstract The use of fiber infrastructures for environmental sensing is attracting global interest, as optical fibers emerge low cost and easily accessible platforms exhibiting a large terrestrial deployment. Moreover, networks offer the unique advantage providing observations submarine areas, where sparse existence permanent seismic instrumentation due to difficulties in deployment limits availability high-resolution subsea information on natural hazards both time space. techniques that...
Abstract A new shear wave velocity model offshore Southern California is presented that images plate boundary deformation including both thickening and thinning of the crustal mantle lithosphere at westernmost edge North American continent. The Asthenospheric Lithospheric Broadband Architecture from Offshore Region Experiment (ALBACORE) ocean bottom seismometer array, together with 65 stations onshore Seismic Network, used to measure ambient noise correlation functions Rayleigh dispersion...
Abstract As seismic traveltime tomography continues to be refined using data from the vast USArray set, it is advantageous also exploit amplitude information carried by waves. We use ambient noise cross correlation make observations of surface wave amplification and attenuation at shorter periods (8–32 s) than can observed with only traditional teleseismic earthquake sources. show that wavefront tracking approach successfully applied correlations, yielding results quite similar those...
SUMMARY We present a theory and conceptual examples for fibre-optic deformation sensing based on phase changes of transmitted light. As first result, we establish an exact relation between observable the tensor along fibre. This is nonlinear includes effects related to both local in fibre length deformation-induced refractive index. In cases where norm much smaller than 1, useful first-order can be derived. It connects integral over in-line strain times When spatial variations index are...
SUMMARY A wide spectrum of processing schemes is commonly applied during the calculation seismic noise correlations. This intended to suppress large-amplitude transient and monochromatic signals, accelerate convergence correlation process or modify raw correlations into more plausible approximations interstation Green’s functions. Many schemes, such as one-bit normalization various other nonlinear normalizations, clearly break linear physics wave propagation. naturally raises question: To...
Abstract During February 2023, a total of 32 individual distributed acoustic sensing (DAS) systems acted jointly as global seismic monitoring network. The aim this Global DAS Month campaign was to coordinate diverse network organizations, instruments, and file formats gain knowledge move toward the next generation earthquake networks. campaign, 156 earthquakes magnitude 5 or larger were reported by U.S. Geological Survey contributors shared data for 60 min after each event’s origin time....
SUMMARY In the immediate vicinity of a source, there are strong gradients in seismic wavefield that tamed and modified distributed acoustic sensing (DAS) recording due to combined effects gauge-length averaging local stacking on strain field. Close source broadside propagation significant, produce characteristic impact DAS channels. presence topography, surface or cable, additional introduced modify expected signal. All these influences mean results tap tests used calibrate channel positions...
Distributed Acoustic Sensing (DAS) has become a popular method of observing seismic wavefields: backscattered pulses light reveal strains or strain-rates at any location along fiber-optic cable. In contrast, few newer systems transmit through cable and collect integrated phase delays over the entire cable, such as Microwave Frequency Fiber Interferometer (MFFI). These can be deployed significantly longer distances, may used in conjunction with live telecommunications, cheaper. However, they...
Abstract We present a workflow for producing shallow subsurface velocity models from passive urban distributed acoustic sensing (DAS) data. This method is demonstrated using dataset collected in Bern, Switzerland, situ telecommunications fiber. compute noise correlations to extract Rayleigh-wave dispersion curves, which we then use produce series of overlapping 1D the top tens meters subsurface. represents realistic “best-case” scenario when real fiber—the cable layout linear, its location...
ABSTRACT The presence of sediments near the Earth’s surface can significantly amplify strength shaking during earthquakes. Such basin or site amplification effects have been well documented in numerous regions, yet complex and often situational dependence competing reasons for this makes it hard to quantify a general sense determine most significant contributions. Simple 1D seismic profiles be used estimate amplitude differences between hard-rock reference site, but ignores any reflections...
SUMMARY Beamforming and backprojection methods offer a data-driven approach to image noise sources, but provide no opportunity account for prior information or iterate through an inversion framework. In contrast, recent have been developed locate ambient sources based on cross-correlations between stations the construction of finite-frequency kernels, allowing inversions over multiple iterations. These kernel-based approaches show great promise, both in mathematical rigour results, are less...
Abstract Despite being 770 km away from the epicenter, observed ground motions due to Tohoku earthquake in Osaka Basin were unexpectedly large, with an amplification of more than a factor 20 compared immediately outside basin, and including 2.7 m peak‐to‐peak roof displacements at one high‐rise building. The local exceeded expectations based on standard computations site response by 3, predicted frequencies peak acceleration off least 50%, such discrepancies have not yet been explained...
ABSTRACT Seismometer deployments are often confined to near the Earth’s surface for practical reasons, despite clear advantages of deeper seismometer installations related lower noise levels and more homogeneous conditions. Here, we describe a 3D broadband array deployed at inactive Homestake Mine in South Dakota, which takes advantage infrastructure originally setup mining is now used range scientific experiments. The consists 24 stations, 15 were underground, with depths ranging from 300...
Abstract Seismic ambient noise sources have received increased attention recently, creating new possibilities to study the Earth's subsurface and atmosphere‐ocean‐solid Earth coupling. In efforts locate such using nonlinear finite‐frequency inversions, methodological developments as pre‐computed wavefields spatially variable grids were necessary. These make inversions feasible for secondary microseismic in a frequency range up 0.2 Hz on daily basis. By obtaining starting model inversion...
A fiber-optic cable below T�rkiye’s earthquake-prone metropolis is offering new details about how seismic waves will rattle the city—and demonstrating potential of a bigger monitoring effort.
SUMMARY Fibre-optic sensing based on transmission offer an alternative to scattering-based distributed acoustic (DAS). The ability interrogate fibres that are thousands of kilometres long opens opportunities for studies remote regions, including ocean basins. However, by averaging deformation along the fibre, systems produce integrated instead measurements. They defy traditional interpretations in terms simple seismic phases, thereby inherently requiring a full-waveform approach. For this,...
Abstract The use of fiber infrastructures for environmental sensing is attracting global interest, as optical fibers emerge low cost and easily accessible platforms exhibiting a large terrestrial deployment. Moreover, networks offer the unique advantage providing observations submarine areas, where sparse existence permanent seismic instrumentation due to difficulties in deployment limits availability high-resolution subsea information on natural hazards both time space. techniques that...
This manuscript is concerned with phase changes of signals transmitted through deforming optical fibres. As a first result, it establishes an exact relation between observable and the deformation tensor along fibre. non-linear, includes effects related to both local in fibre length deformation-induced speed light or refractive index. In seismic applications, where norm earthquake-induced orders magnitude smaller than 1, useful first-order can be derived. It simply connects integral over...
Abstract Despite the theory for both Rayleigh and Love waves being well accepted theoretical predictions accurately matching observations, direct observation of their quantifiable decay with depth has never been measured in Earth’s crust. In this work, we present observations surface‐wave eigenfunctions. This is done by making Rayleigh‐wave Love‐wave eigenfunction amplitudes over a range depths using data collected at 3D Homestake array suite nearby mine blasts. Observations frequencies from...