A 3D Broadband Seismometer Array Experiment at the Homestake Mine

2018 ◽  
Vol 89 (6) ◽  
pp. 2420-2429 ◽  
Author(s):  
Vuk Mandic ◽  
Victor C. Tsai ◽  
Gary L. Pavlis ◽  
Tanner Prestegard ◽  
Daniel C. Bowden ◽  
...  
Keyword(s):  
Broadband Seismometer ◽  
Homestake Mine

scholarly journals Integration of onshore and offshore seismic arrays to study the seismicity of the Calabrian Region: a two steps automatic procedure for the identification of the best stations geometry

2014 ◽  
Vol 36 ◽  
pp. 69-75 ◽  
Author(s):  
A. D'Alessandro ◽  
I. Guerra ◽  
G. D'Anna ◽  
A. Gervasi ◽  
P. Harabaglia ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Network Optimization ◽  
A Priori ◽  
Second Step ◽  
Ocean Bottom ◽  
Broadband Seismometer ◽  
Seismic Stations ◽  
Seismic Arrays ◽  
Monitoring Campaign ◽  
Seismographic Network

Abstract. We plan to deploy in the Taranto Gulf some Ocean Bottom broadband Seismometer with Hydrophones. Our aim is to investigate the offshore seismicity of the Sibari Gulf. The seismographic network optimization consists in the identification of the optimal sites for the installation of the offshore stations, which is a crucial factor for the success of the monitoring campaign. In this paper, we propose a two steps automatic procedure for the identification of the best stations geometry. In the first step, based on the application of a set of a priori criteria, the suitable sites to host the ocean bottom seismic stations are identified. In the second step, the network improvement is evaluated for all the possible stations geometries by means of numerical simulation. The application of this procedure allows us to identify the best stations geometry to be achieved in the monitoring campaign.

scholarly journals Seismic investigations of the Martian near-surface at the InSight landing site

2020 ◽  
Author(s):  
Cedric Schmelzbach ◽  
Nienke Brinkman ◽  
David Sollberger ◽  
Sharon Kedar ◽  
Matthias Grott ◽  
...  
Keyword(s):  
Deep Structure ◽  
Landing Site ◽  
P Wave ◽  
Mission Design ◽  
Normal Operation ◽  
Seismic Signals ◽  
Martian Surface ◽  
Broadband Seismometer ◽  
Near Surface ◽  
Martian Regolith

<p>The InSight ultra-sensitive broadband seismometer package (SEIS) was installed on the Martian surface with the goal to study the seismicity on Mars and the deep interior of the Planet. A second surface-based instrument, the heat flow and physical properties package HP<sup>3</sup>, was placed on the Martian ground about 1.1 m away from SEIS. HP<sup>3</sup> includes a self-hammering probe called the ‘mole’ to measure the heat coming from Mars' interior at shallow depth to reveal the planet's thermal history. While SEIS was designed to study the deep structure of Mars, seismic signals such as the hammering ‘noise’ as well as ambient and other instrument-generated vibrations allow us to investigate the shallow subsurface. The resultant near-surface elastic property models provide additional information to interpret the SEIS data and allow extracting unique geotechnical information on the Martian regolith.</p><p>The seismic signals recorded during HP<sup>3</sup> mole operations provide information about the mole attitude and health as well as shed light on the near-surface, despite the fact that the HP<sup>3 </sup>mole continues to have difficulty penetrating below 40 cm (one mole length). The seismic investigation of the HP<sup>3</sup> hammering signals, however, was not originally planned during mission design and hence faced several technical challenges. For example, the anti-aliasing filters of the seismic-data acquisition chain were adapted when recording the mole hammering to allow recovering information above the nominal Nyquist frequency. In addition, the independently operating SEIS, HP<sup>3</sup> and lander clocks had to be correlated more frequently than in normal operation to enable high-precision timing.</p><p>To date, the analysis of the hammering signals allowed us to constrain the bulk P-wave velocity of the volume between the mole tip and SEIS (top 30 cm) to around 120 m/s. This low velocity value is compatible with laboratory tests performed on Martian regolith analogs with a density of around 1500 kg/m<sup>3</sup>. Furthermore, the SEIS leveling system resonances, seismic recordings of atmospheric pressure signals, HP<sup>3</sup> housekeeping data, and imagery provide additional constraints to establish a first seismic model of the shallow (topmost meters) subsurface at the landing site.</p>

scholarly journals Broadband waveforms and site effects at a borehole seismometer in the Po alluvial basin (Italy)

2001 ◽  
Vol 44 (1) ◽  
Author(s):  
M. Cocco ◽  
F. Ardizzoni ◽  
R. M. Azzara ◽  
L. Dall'Olio ◽  
A. Delladio ◽  
...  
Keyword(s):  
Site Effects ◽  
Velocity Structure ◽  
Dynamic Range ◽  
Site Response ◽  
Seismic Exploration ◽  
Ratio Method ◽  
Data Set ◽  
Broadband Seismometer ◽  
Local Earthquakes ◽  
Teleseismic Events

Broadband seismograms recorded at a borehole three-component (high dynamic range) seismic station in the Po Valley (Northern Italy) were analyzed to study the velocity structure of the shallow sedimentary layers as well as the local site effects in soft sediments. The broadband borehole seismometer was installed at a depth of 135 m just below the quaternary basement, while a second digital broadband seismometer was installed in the same site at the Earth surface. The velocity structure in the shallower layers was determined both by means of cross-hole and up-hole measurements and by inverting seismic data recorded during a seismic exploration experiment.Velocity discontinuities are quite well related to the stratigraphy of the site. We are interested to record local earthquakes as well as regional and teleseismic events. The analyzed data set includes local, regional and teleseismic events, most of which were recorded during the seismic sequence that started on October 15, 1996, near Reggio Emilia 80 km away from the borehole site. The orientation of the borehole sensor is determined using the recordings of a teleseismic event and of some local earthquakes. The noise reduction for the borehole sensor is 2 decades in power spectral density at frequencies larger than 1.0 Hz. We studied the site amplification of the shallow alluvial layers by applying the spectral ratio method. We analyzed the spectral ratios of noise recorded by the surface and borehole seismometers as well as those from local earthquakes. We compared these observations with a theoretical model for the site response computed by the Haskell-Thomson method.

Distributed Acoustic Sensing Using Dark Fiber for Array Detection of Regional Earthquakes

2021 ◽  
Author(s):  
Avinash Nayak ◽  
Jonathan Ajo-Franklin ◽  
Keyword(s):  
Urban Areas ◽  
Geothermal Field ◽  
Seismic Events ◽  
Broadband Seismometer ◽  
Acoustic Sensing ◽  
Array Detection ◽  
Distributed Acoustic Sensing ◽  
Back Azimuth ◽  
Ubiquitous Presence

Abstract The intrinsic array nature of distributed acoustic sensing (DAS) makes it suitable for applying beamforming techniques commonly used in traditional seismometer arrays for enhancing weak and coherent seismic phases from distant seismic events. We test the capacity of a dark-fiber DAS array in the Sacramento basin, northern California, to detect small earthquakes at The Geysers geothermal field, at a distance of ∼100  km from the DAS array, using beamforming. We use a slowness range appropriate for ∼0.5–1.0  Hz surface waves that are well recorded by the DAS array. To take advantage of the large aperture, we divide the ∼20  km DAS cable into eight subarrays of aperture ∼1.5–2.0  km each, and apply beamforming independently to each subarray using phase-weighted stacking. The presence of subarrays of different orientations provides some sensitivity to back azimuth. We apply a short-term average/long-term average detector to the beam at each subarray. Simultaneous detections over multiple subarrays, evaluated using a voting scheme, are inferred to be caused by the same earthquake, whereas false detections caused by anthropogenic noise are expected to be localized to one or two subarrays. Analyzing 45 days of continuous DAS data, we were able to detect all earthquakes with M≥2.4, while missing most of the smaller magnitude earthquakes, with no false detections due to seismic noise. In comparison, a single broadband seismometer co-located with the DAS array was unable to detect any earthquake of M<2.4, many of which were detected successfully by the DAS array. The seismometer also experienced a large number of false detections caused by spatially localized noise. We demonstrate that DAS has significant potential for local and regional detection of small seismic events using beamforming. The ubiquitous presence of dark fiber provides opportunities to extend remote earthquake monitoring to sparsely instrumented and urban areas.

scholarly journals The InSight Blind Test: An Opportunity to Bring a Research Dataset into Teaching Programs

2020 ◽  
Vol 91 (2A) ◽  
pp. 1064-1073
Author(s):  
Julien Balestra ◽  
Jean-Luc Berenguer ◽  
Florence Bigot-Cormier ◽  
Françoise Courboulex ◽  
Lucie Rolland ◽  
...  
Keyword(s):  
High School Students ◽  
Real Data ◽  
School Students ◽  
Blind Test ◽  
Broadband Seismometer ◽  
Waveform Data ◽  
Scientific Challenge ◽  
Teaching Programs ◽  
Short Time ◽  
Insight Mission

Abstract On 26 November 2019, SEIS, the first broadband seismometer designed for the Martian environment (Lognonné et al., 2019) landed on Mars, thanks to National Aeronautics and Space Administration’s (NASA’s) InSight mission. On 6 April 2019 (sol 128), the InSight Science team detected the first historical “marsquake” (NASA news release). Before it was recorded, the InSight Science team developed the InSight blind test (hereafter, IBT), which consists of a 12-month period of continuous waveform data combining realistic estimates of Martian background seismic noise, 204 tectonic, and 35 impact events (Clinton et al., 2017). This project was originally designed to prepare scientists for the arrival of real data from the upcoming InSight mission. This article presents the work carried out by middle and high school students during this challenge. This project offered schools the opportunity to participate in and strengthen the link between secondary schools and universities. The IBT organizers accepted the approach to enable 14 schools to take part in this scientific challenge. After a training process, each school analyzed the IBT dataset to contribute to the collaborative School Team catalog. The schools relied on a manual procedure combining analyses in time and frequency domains. At the end, a combined catalog was submitted as one of the IBT entries. The IBT organizers then assessed the catalog submitted by the consortium of schools together with the results from science teams (Van Driel et al., 2019). The schools achieved a total of 15 correct detections over a short time period. Although this number may seem modest compared with the 239 synthetic marsquakes included in the IBT waveform data, these correct detections were entirely made during class time. All in all, the students seemed to be fully engaged, and this exercise seemed to increase their scientific inquiry skills to fulfill their task as a team.

Direct P-wave anisotropy measurements at Homestake Mine: implications for wave propagation in continental crust

2020 ◽  
Vol 224 (1) ◽  
pp. 121-137
Author(s):  
James Atterholt ◽  
Sarah J Brownlee ◽  
Gary L Pavlis
Keyword(s):  
Wave Propagation ◽  
Particle Motion ◽  
Bootstrap Method ◽  
Estimation Method ◽  
Principal Component ◽  
Compressional Wave ◽  
P Wave ◽  
Longitudinal Motion ◽  
Angular Deviation ◽  
Homestake Mine

SUMMARY We measured anisotropic seismic properties of schists of the Homestake Formation located at a depth of 1478 m in the Sanford Underground Research Facility (SURF) in the Black Hills of South Dakota, USA. We deployed a 24-element linear array of three-component geophones in an area in the Homestake Mine called 19-ledge. An airless jackhammer source was used to shoot two profiles: (1) a walkaway survey to appraise any distance dependence and (2) a fan shot profile to measure variations with azimuth. Slowness estimates from the fan shot profile show a statistically significant deviation with azimuth with the expected 180° variation with azimuth. We measured P-wave particle motion deviations from data rotated to ray coordinates using three methods: (1) a conventional principal component method, (2) a novel grid search method that maximized longitudinal motion over a range of search angles and (3) the multiwavelet method. The multiwavelet results were computed in two frequency bands of 200–600 and 100–300 Hz. Results were binned by azimuth and averaged with a robust estimation method with error bars estimated by a bootstrap method. The particle motion results show large, statistically significant variations with azimuth with a 180° cyclicity. We modelled the azimuthal variations in compressional wave speed and angular deviation from purely longitudinal particle motion of P-waves using an elastic tensor method to appraise the relative importance of crystalline fabric relative to fracturing parallel to foliation. The model used bulk averages of crystal fabric measured for an analogous schist sample from southeast Vermont rotated to the Homestake Formation foliation directions supplied by SURF from old mine records. We found with average crustal crack densities crack induced anisotropy had only a small effect on the observables. We found strong agreement in the traveltime data. The observed amplitudes of deviations of P particle motion showed significantly larger variation than the model predictions and a 20° phase shift in azimuth. We attribute the inadequacies of the model fit to the particle motion data to inadequacies in the analogue rock and/or near receiver distortions from smaller scale heterogeneity. We discuss the surprising variability of signals recorded in this experimental data. We show clear examples of unexplained resonances and unexpected variations on a scale much smaller than a wavelength that has broad implications for wave propagation in real rocks.

The ROMY project: A 4-component ring laser for geophysics and geodesy

2020 ◽  
Author(s):  
Heiner Igel ◽  
Felix Bernauer ◽  
Joachim Wassermann ◽  
Shihao Yuan ◽  
Andre Gebauer ◽  
...  
Keyword(s):  
Ground Motion ◽  
Ring Laser ◽  
High Sensitivity ◽  
Point Of View ◽  
Small Scale ◽  
Broadband Seismometer ◽  
Rotational Ground Motion ◽  
Noise Characteristics ◽  
The Individual ◽  
Redundant Component

<p>The ROMY ring laser was constructed with 4 non-orthogonal triangular-shaped cavities of 12 m side length in the Geophysical Observatory outside Munich, Germany, in 2016. The large dimensions of the individual rings have the benefit of allowing high sensitivity surpassing in principle the sensitivity of the G-ring at the Fundamentalstation Wettzell. However, the concrete construction of ROMY is geometrically less stable than the G-ring that is built on a rigid Xerodur plate. Each of the four rings has its own Sagnac frequency. The horizontal triangular ring laser at the top of the inverted tetrahedral ROMY structure allows direct comparison of teleseismic signals and noise with the G-ring at a distance of 200km. It also serves as redundant component. In principle, three orthogonal components of rotational ground motion can be obtained by linear combination from any combination of three rings, that - due to the variable Sagnac frequency - have different noise characteristics. We report on the behavior and observations of ROMY from a seismological point of view. It is fair to say that ROMY provides the most accurate direct 3-component rotational ground motion seismic observations to date. In combination with a collocated broadband seismometer as well as a surrounding small-scale seismic array, we analyse regional, teleseismic events, and ocean-generated noise and compare with array-derived rotation.</p>

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