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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Global seismic attenuation imaging using full-waveform inversion: a comparative assessment of different choices of misfit functionals

We present the results of synthetic tests that aim at evaluating the relative performance of three different definitions of misfit functionals in the context of 3-D imaging of shear wave attenuation in the earth’s upper mantle at the global scale, using long-period full-waveform data. The synthetic tests are conducted with simple hypothetical upper-mantle models that contain Q μ anomalies centred at different depths and locations, with or without additional seismic velocity anomalies. To build synthetic waveform data sets, we performed simulations of 50 events in the hypothetical (target) models, using the spectral element method, filtered in the period range 60–400 s. The selected events are chosen among 273 events used in the development of radially anisotropic model SEMUCB-WM1 and recorded at 495 stations worldwide. The synthetic Z-component waveforms correspond to paths and time intervals (fundamental mode and overtone Rayleigh waves) that exist in the real waveform data set. The inversions for shear attenuation structure are carried out using a Gauss–Newton optimization scheme in which the gradient and Hessian are computed using normal mode perturbation theory. The three different misfit functionals considered are based on time domain waveform (WF) and waveform envelope (E-WF) differences, as well as spectral amplitude ratios (SA), between observed and predicted waveforms. We evaluate the performance of the three misfit functional definitions in the presence of seismic noise and unresolved S-wave velocity heterogeneity and discuss the relative importance of physical dispersion effects due to 3-D Q μ structure. We observed that the performance of WF is poorer than the other two misfit functionals in recovering attenuation structure, unless anelastic dispersion effects are taken into account in the calculation of partial derivatives. WF also turns out to be more sensitive to seismic noise than E-WF and SA. Overall, SA performs best for attenuation imaging. Our tests show that it is important to account for 3-D elastic effects (focusing) before inverting for Q μ . Additionally, we show that including high signal-to-noise ratio overtone wave packets is necessary to resolve Q μ structure at depths greater than 250 km.

58 GEOSCIENCES↗
DOE OSTI2018

Shallow three-dimensional structure of the San Jacinto fault zone revealed from ambient noise imaging with a dense seismic array

In this work, we use 1 month of continuous seismic waveforms from a very dense seismic network to image with unprecedented resolution the shallow damage structure of the San Jacinto fault zone across the Clark fault strand. After calculating noise correlations, high apparent velocity arrivals coming from below the array are removed using a frequency–wavenumber filter. This is followed by a double-beamforming analysis on multiple pairs of subarrays to extract phase and group velocity information across the study area. The phase and group velocity dispersion curves are regionalized into phase and group velocity maps at different frequencies, and these maps are inverted using a neighbourhood algorithm to build a 3-D shear wave velocity model around the Clark fault down to ~500 m depth. The model reveals strong lateral variations across the fault strike with pronounced low-velocity zones corresponding to a local sedimentary basin and a fault zone trapping structure. The results complement previous earthquake- and seismic noise-based imaging of the fault zone at greater depth and clarify properties of structural features near the surface.

58 GEOSCIENCES↗
DOE OSTI2017

2D Seismic Profiles, Nevada Play Fairway - Granite Springs Valley

This data is associated with the Nevada Play Fairway project and contains 2D seismic profile data in cropped jpegs and tiffs, both interpreted and uninterpreted. Seismic data owned or controlled by Seismic Exchange, Inc.; interpretation is that of the University of Nevada, Reno.

15 GEOTHERMAL ENERGY↗
DOE OSTI2016

Passive Seismic Emission Tomography Results at San Emidio Nevada

The utility of passive seismic emission tomography for mapping geothermal permeability has been tested at San Emidio in Nevada. The San Emidio study area overlaps a geothermal field in production since 1987 and another resource to the south of the production field. Passive seismic data collections were completed at San Emidio in late 2016 by Microseismic Inc as part of a DOE project. The PSET results are being analyzed as part of the WHOLESCALE project. This submission includes P-wave velocity model data, and the passive seismic data with more information on each bellow.

15 GEOTHERMAL ENERGY↗
DOE OSTI2023

Utah FORGE: Fault Shear Reactivation Experimental Data for Fluid Injection-Rate Controls on Seismic Moment

Included are experimental data recorded from shear experiments that specifically explore the link between fluid-injection rate and seismic moment resulting from shear reactivation of laboratory faults. Raw mechanical data from three experiments are included alongside corresponding MATLAB scripts that import and plot the data, as well as use it to calculate shear and normal stress. Experiments are performed on 2.5-3 inch long granitoid cores from the Utah FORGE EGS demonstration site, containing a single inclined fracture with small-scale roughness added to the fracture surface. The raw data included here were recorded from an aluminum triaxial pressure vessel (TEMCO) configured with three independent servo-controlled pumps, with distilled water used as the working fluid. The pumps control confining pressure, upstream pore pressure, and axial pressure, with each pump connected to a LabView interface to record applied pressures, cumulative injected water volumes, and pump flow rates. The downstream outlet from the fracture is closed to allow pressurization, which is measured by an external pressure transducer. A linear variable differential transformer (LVDT) attached to the axial piston measures axial displacement, from which we calculate shear displacement along the fracture. Additionally, P-wave transducers are used to record acoustic signatures, where acoustic emission events and maximum amplitudes are compared against seismic moment and shear slip velocity. Fluid injection rates range between 0.05 mL/min, 0.25 mL/min, and 0.75 mL/min for each experiment. Along-fault pressure distributions are progressively less uniform as injection rates increase, representing a switch from steady-state to transient conditions. Triggered shear displacement is used as a proxy for seismic moment and is indexed against cumulative injection volume and rate. Each experiment is performed under constant shear stress conditions, and the sample is fully saturated with DI water. Axial and confining stresses are applied to 3 MPa through pressure-stepping in 500 kPa increments. The pore pressure is held constant at 200 kPa prior to initiating the experiment, and initial axial displacement is recorded. The axial stress is then increased to initiate shear mobilization during the loading phase (run-in) until a peak steady state is achieved. The initial shear stress is reduced to approximately 80% of the peak shear stress by decreasing the axial stress, then held constant for the duration of each experiment.

15 GEOTHERMAL ENERGY↗
DOE OSTI2025

EGS Collab Experiment 2: Continuous Active Source Seismic Monitoring (CASSM)

The dataset contains continuous active-source seismic monitoring (CASSM) data collected during EGS Collab Experiment 2, conducted from February to September 2022 at the Sanford Underground Research Facility in Lead, South Dakota. This experiment aimed to investigate enhanced geothermal systems through high-pressure fluid injections at depths of 1200-1500 meters. The seismic monitoring system included 16 three-component piezoelectric accelerometers and 24 hydrophones installed in boreholes around the injection zones, recording signals from piezoelectric seismic sources. Data were acquired using both continuous and triggered recording systems, with sampling rates of up to 100 kHz. The raw data are organized by timestamps and stored in .dat format, with accompanying log files. Calibration certificates for selected accelerometers are provided to aid in correcting sensor responses, though users are advised to consider possible effects of enclosures and installation on sensor performance. Users are strongly advised to consult the accompanying report, which outlines the experimental setup, data acquisition, sensor specifications, and recording systems.

15 GEOTHERMAL ENERGY↗
DOE OSTI2023

The Seismic Signature of a High-Energy Density Physics Laboratory and Its Potential for Measuring Time-Dependent Velocity Structure

The Z Machine at Sandia National Laboratories is a pulsed power facility for high-energy density physics experiments that can shock materials to extreme temperatures and pressures through a focused energy release of up to ~ 25 MJ in < 100 nanoseconds. It has been in operation for more than two decades and conducts up to ~ 100 experiments, or “shots,” per year. Based on a set of 74 known shot times from 2018, we determined that Z Machine shots produce detectable ~ 3–17 Hz ground motion 12 km away at the Albuquerque Seismological Laboratory, New Mexico (ANMO), borehole seismograph, with peak signal at ~ 7 Hz. The known shot waveforms were used to create a three-component template, leading to the detection of 2339 Z Machine shots since 1998 through single-station cross-correlation. Local seismic magnitude estimates range from local magnitude (M L ) —2 to —1.3 and indicate that only a small fraction of the shot energy is transmitted by seismic phases observable at 12 km distance. The most recent major facility renovation, which was intended to decrease mechanical dissipation, is associated with an abrupt decrease in observed seismic amplitudes at ANMO despite stable maximum shot energy. The highly repetitive impulsive sources are well suited to coda-wave interferometry to investigate time-dependent velocity structures. Relative velocity variations (dv/v) show an annual cycle with amplitude of ~ 0.2%. Local minima are observed in the late spring, and dv/v increases through the summer monsoon rainfall, possibly reflecting patchy saturation as rainfall infiltrates near the eastern edge of the Albuquerque basin. Importantly, the cumulative results demonstrate that forensic seismology can provide insight into long-term operation of facilities such as pulsed-power laboratories, and that their recurring signals may be valuable for studies of time-dependent structure

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

PySolate : A Python‐Based Thresholding Tool to Denoise or Designal Seismic Waveforms Based on the Continuous Wavelet Transform

PySolate is a Python‐based toolset that implements the continuous wavelet transform and nonlinear thresholding operations to denoise or designal seismic data, following Langston and Mousavi (2019). This filtering approach can remove microseismic noise to isolate intermediate‐period seismic signals that are key to enabling full‐waveform modeling and analysis of smaller‐magnitude regional events. This approach is best for the application to signals with frequency or time separation of signal and noise, in contrast to Fourier analysis, which is effective when signal and noise are separated in frequency. We demonstrate the Python toolset using the six announced Democratic People’s Republic of Korea declared nuclear tests, showing the effectiveness of isolating the seismic signal compared to standard bandpass filtering. In conclusion, we also demonstrate the ease of using the toolset with any Python processing tools.

Asia↗
DOE OSTI2016

INL Seismic Monitoring Annual Report: January 1, 2013 to December 31, 2013

During 2013, the Idaho National Laboratory (INL) recorded 14,011 independent triggers and 7,355 triggers were manmade blasts and distant, regional, and local earthquakes. Within the region, the INL Seismic Monitoring program located 2,085 earthquakes and 150 man-made blasts. Near and within the 161-km radius of INL, 38 of these earthquakes had small to moderate size magnitudes that ranged from 3.0 to 4.2. Residents near 19 of the M>3.0 earthquakes reported ground shaking affects of these earthquakes to the U.S. Geological Survey. Also, five new seismic stations with broadband seismometers and accelerometers were installed near INL facility areas. These new stations were installed to collect earthquake data that can be used in future INL probabilistic seismic hazard analyses to reduce uncertainties of ground motion models. In 2013, 1,013 earthquakes were located within the 161-km radius of INL and three occurred within the eastern Snake River Plain (ESRP). The earthquakes included three swarms and a mainshock-aftershock sequence. The earthquakes were located northwest of the INL in the Basin and Range regions of Idaho and Montana and southeast of the ESRP in the Basin and Range region along the Idaho-Wyoming border. A swarm of >180 earthquakes occurred at Driggs, Idaho; the largest events had local magnitudes (ML) of 2.8 and 3.1 and were felt by residents. A less intense swarm of 64 earthquakes was located west of Jackson, Wyoming along the Idaho-Wyoming border. The largest event was a MW 3.8 that was felt by local residents. Southeast of Pocatello, Idaho an earthquake of ML 4.2 was followed by 18 aftershocks that included a ML 3.6. Both earthquakes were felt by residents near to the epicenters. Three earthquakes occurred within the ESRP and three other earthquakes were located at the northwest edge of the ESRP. The coda magnitude (Mc) 1.3 earthquake was located in the center of ESRP north of the Great Rift and at a depth of 45 km. To the west, an earthquake of Mc 0.7 was located at a depth of 37 km and at the northwestern end of the Great Rift. Four earthquakes, Mc 0.0, Mc 1.3, Mc 1.8, and Mc 1.1 were located north of the INL along the edge of the ESRP. The Mc 0.0 and 1.1 earthquakes were located just within the ESRP at depths less than 6 km.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Seismic Monitoring at the Farnsworth CO2-EOR Field Using Time-Lapse Elastic-Waveform Inversion of 3D-3C VSP Data

During the Development Phase of the U.S. Southwest Regional Partnership on Carbon Sequestration, supercritical CO2 was continuously injected into the deep oil-bearing Morrow B formation of the Farnsworth Unit in Texas for Enhanced Oil Recovery (EOR). The project injected approximately 94 kilotons of CO2 to study geologic carbon storage during CO2-EOR. A three-dimensional (3D) surface seismic dataset was acquired in 2013 to characterize the subsurface structures of the Farnsworth site. Following this data acquisition, the baseline and three time-lapse three-dimensional three-component (3D-3C) vertical seismic profiling (VSP) data were acquired at a narrower surface area surrounding the CO2 injection and oil/gas production wells between 2014 and 2017 for monitoring CO2 injection and migration. With these VSP datasets, we inverted for subsurface velocity models to quantitatively monitor the CO2 plume within the Morrow B formation. We first built 1D initial P-wave (Vp) and S-wave (Vs) velocity models by upscaling the sonic logs. We improved the deep region of the Vp and Vs models by incorporating the deep part of a migration velocity model derived from the 3D surface seismic data. We improved the shallow region of 3D Vp and Vs models using 3D traveltime tomography of first arrivals of VSP downgoing waves. We further improved the 3D baseline velocity models using elastic-waveform inversion (EWI) of the 3D baseline VSP upgoing data. Our advanced EWI method employs alternative tomographic and conventional gradients and total-variation-based regularization to ensure the high-fidelity updates of the 3D baseline Vp and Vs models. We then sequentially applied our 3D EWI method to the three time-lapse datasets to invert for spatiotemporal changes of Vp and Vs in the reservoir. Our inversion results reveal the volumetric changes of the time-lapse Vp and Vs models and show the evolution of the CO2 plume from the CO2 injection well to the oil/gas production wells.

42 ENGINEERING↗
DOE OSTI2021

Gaussian Kernel Methods for Seismic Fragility and Risk Assessment of Mid-Rise Buildings

Seismic fragility functions can be evaluated using the cloud analysis method with linear regression which makes three fundamental assumptions about the relation between structural response and seismic intensity: log-linear median relationship, constant standard deviation, and Gaussian distributed errors. While cloud analysis with linear regression is a popular method, the degree to which these individual and compounded assumptions affect the fragility and the risk of mid-rise buildings needs to be systematically studied. This paper conducts such a study considering three building archetypes that make up a bulk of the building stock: RC moment frame, steel moment frame, and wood shear wall. Gaussian kernel methods are employed to capture the data-driven variations in the median structural response and standard deviation and the distributions of residuals with the intensity level. With reference to the Gaussian kernels approach, it is found that while the linear regression assumptions may not affect the fragility functions of lower damage states, this conclusion does not hold for the higher damage states (such as the Complete state). In addition, the effects of linear regression assumptions on the seismic risk are evaluated. For predicting the demand hazard, it is found that the linear regression assumptions can impact the computed risk for larger structural response values. However, for predicting the loss hazard with downtime as the decision variable, linear regression can be considered adequate for all practical purposes.

58 GEOSCIENCES↗
DOE OSTI2018

High-resolution 3D seismic acquisition at the Tomakomai CO2 storage project, offshore Hokkaido, Japan

Monitoring injected CO2 is an important part of assuring permanence of long term storage to mitigate atmospheric emissions. Three-dimensional (3D) seismic has been shown to be an effective technology for visualizing and measuring subsurface geology and fluids. In this study, we demonstrate the successful acquisition, processing and initial interpretation of a high-resolution 3D (HR3D) seismic survey in Tomakomai, offshore Japan, above an active offshore CO2 injection site. The successful deployment of this novel marine seismic monitoring technology validates HR3D as an appropriate characterization and monitoring tool for large- demonstration and commercial-scale offshore Carbon Capture and Storage (CCS) sites.

Carbon Capture and Storage (CCS)↗
DOE OSTI2016

Seismic velocity changes associated with aseismic deformations of a fault stimulated by fluid injection

Fluid pressure plays an important role in the stability of tectonic faults. However, the in situ mechanical response of faults to fluid pressure variations is still poorly known. To address this question, we performed here a fluid injection experiment in a fault zone in shales while monitoring fault movements at the injection source and seismic velocity variations from a near-distance (<10 m) monitoring network. We measured and located the P and S wave velocity perturbations in and around the fault using repetitive active sources. We observed that seismic velocity perturbations dramatically increase above 1.5 MPa of injection pressure. This is consistent with an increase of fluid flow associated with an aseismic dilatant shearing of the fault as shown by numerical modeling. We find that seismic velocity changes are sensitive to both fault opening by fluid invasion and effective stress variations and can be an efficient measurement for monitoring fluid-driven aseismic deformations of faults.

58 GEOSCIENCES↗
DOE OSTI2017

On the physics-based processes behind production-induced seismicity in natural gas fields

Induced seismicity due to natural gas production is observed at different sites worldwide. Common understanding states that the pressure drop caused by gas production leads to compaction, which affects the stress field in the reservoir and the surrounding rock formations and hence reactivates preexisting faults and induces earthquakes. We show that the multiphase fluid flow involved in natural gas extraction activities should be included. We use a fully coupled fluid flow and geomechanics simulator, which accounts for stress-dependent permeability and linear poroelasticity, to better determine the conditions leading to fault reactivation. In our model setup, gas is produced from a porous reservoir, divided into two compartments that are offset by a normal fault. Results show that fluid flow plays a major role in pore pressure and stress evolution within the fault. Fault strength is significantly reduced due to fluid flow into the fault zone from the neighboring reservoir compartment and other formations. We also analyze scenarios for minimizing seismicity after a period of production, such as (i) well shut-in and (ii) gas reinjection. In the case of well shut-in, a highly stressed fault zone can still be reactivated several decades after production has ceased, although on average the shut-in results in a reduction in seismicity. In the case of gas reinjection, fault reactivation can be avoided if gas is injected directly into the compartment under depletion. However, gas reinjection into a neighboring compartment does not stop the fault from being reactivated.

03 NATURAL GAS↗
DOE OSTI2017

Sensitivity of Induced Seismic Sequences to Rate-and-State Frictional Processes

It is well established that subsurface injection of fluids increases pore fluid pressures that may lead to shear failure along a preexisting fault surface. Concern among oil and gas, geothermal, and carbon storage operators has risen dramatically over the past decade due to the increase in the number and magnitude of induced earthquakes. Efforts to mitigate the risk associated with injection-induced earthquakes include modeling of the interaction between fluids and earthquake faults. Here we investigate this relationship with simulations that couple a geomechanical reservoir model and RSQSim, a physics-based earthquake simulator. RSQSim employs rate- and state-dependent friction (RSF) that enables the investigation of the time-dependent nature of earthquake sequences. We explore the effect of two RSF parameters and normal stress on the spatiotemporal characteristics of injection-induced seismicity. We perform >200 simulations to systematically investigate the effect of these model components on the evolution of induced seismicity sequences and compare the spatiotemporal characteristics of our synthetic catalogs to observations of induced earthquakes. We find that the RSF parameters control the ability of seismicity to migrate away from the injection well, the total number and maximum magnitude of induced events. Additionally, the RSF parameters control the occurrence/absence of premonitory events. Finally, we find that earthquake stress drops can be modulated by the normal stress and/or the RSF parameters. Insight gained from this study can aid in further development of models that address best practice protocols for injection operations, site-specific models of injection-induced earthquakes, and probabilistic hazard and risk assessments.

58 GEOSCIENCES↗
DOE OSTI2023

Mid–height seismic isolation of equipment in nuclear power plants

An innovative seismic isolation solution for designers of safety-class equipment in advanced nuclear power plants is introduced. The test specimen was a tall, slender, carbon steel vessel that could represent a reactor vessel, steam generator, or a heat exchanger in a nuclear power plant: 240 inches tall, outer diameter of 60 inches, and wall thickness of 1 inch. The vessel was supported by three radial mounts at its mid-height, near its center of gravity, on a steel frame. The vessel was subjected to three-component ground motions using a 6DOF earthquake simulator. The specimen was filled with water for testing to indirectly account for the fluid and internal equipment present inside a prototype vessel. Three configurations were tested: non-isolated, isolated using single Friction Pendulum (SFP) bearings, and isolated using triple Friction Pendulum (TFP) bearings. The test results demonstrate that mid-height seismic isolation is practical and enables a significant reduction in horizontal spectral accelerations. Furthermore, these outcomes are not specific to the spherical sliding bearings used in the experiments but are broadly applicable to mid-height, seismically isolated equipment.

42 ENGINEERING↗
DOE OSTI2021

Updates to the Regional Seismic Travel Time (RSTT) Model: 2. Path-dependent Travel-time Uncertainty

Abstract The regional seismic travel time (RSTT) model and software were developed to improve travel-time prediction accuracy by accounting for three-dimensional crust and upper mantle structure. Travel-time uncertainty estimates are used in the process of associating seismic phases to events and to accurately calculate location uncertainty bounds (i.e. event location error ellipses). We improve on the current distance-dependent uncertainty parameterization for RSTT using a random effects model to estimate slowness (inverse velocity) uncertainty as a mean squared error for each model parameter. The random effects model separates the error between observed slowness and model predicted slowness into bias and random components. The path-specific travel-time uncertainty is calculated by integrating these mean squared errors along a seismic-phase ray path. We demonstrate that event location error ellipses computed for a 90% coverage ellipse metric (used by the Comprehensive Nuclear-Test-Ban Treaty Organization International Data Centre (IDC)), and using the path-specific travel-time uncertainty approach, are more representative (median 82.5% ellipse percentage) of true location error than error ellipses computed using distance-dependent travel-time uncertainties (median 70.1%). We also demonstrate measurable improvement in location uncertainties using the RSTT method compared to the current station correction approach used at the IDC (median 74.3% coverage ellipse).

58 GEOSCIENCES↗