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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Seismic-velocity inversion using surface-wave tomography

© 2018 SEG. In this paper, we present the workflow of the application of surface wave tomography to characterize the near surface. A near surface model is simulated with a shallow unconsolidated layer that has a variable thickness and a deep consolidated zone. Data is filtered by bandpass filters and surface wave phase arrival times are picked, and surface wave velocities are inverted using a ray theoretical tomographic approach. A good agreement is found between the inverted results and the original model. In another model, a thin fault zone is detected. Agreement between the tomographic results and the model suggests that surface wave tomography is well suited for characterizing shallow geology with the capability of identifying low velocity anomalies and general lateral variations.

Wu, Zheshu↗
DOE OSTI2022

Utah FORGE Friction-Permeability-Seismicity Laboratory Experiments with Non-Linear Acoustics

Laboratory experimental data on saw-cut interface of Westerly Granite and Utah Forge granitoid rocks. Experiments include velocity-stepping and fluid pressure stepping experiments. Mechanical data from 3 ISCO pumps connected to a Temco pressure vessel measure axial, confining and fault: fluid pressure (kPa), fluid flow rate (mL/min) and volume remaining in pump (mL). Non-linear acoustic data acquired via Verasonics systems connected to PZTs inside the pressure vessel give the timeshift, amplitude and RMS amplitude of the passing P-wave.

15 GEOTHERMAL ENERGY↗
DOE OSTI2016

Evaluation of a Seismic Event, 12 May 2010, in North Korea

We assess seismological evidence bearing on claims that North Korea conducted a small nuclear test on 12 May 2010 in the vicinity of known underground nuclear tests in 2006, 2009, 2013, and 2016. First, we use Lg -wave cross-correlation and more traditional methods to locate the 2010 event between about 4 and 10 km southwest of the 2009 test. Second, we compare the relative sizes of regional P-waves and S-waves, using stations within 400 km of the known North Korean nuclear tests, to assess the nature of the event. We measured P / S ratios at different frequencies, at first using data from the open station MDJ in northeast China, for training sets of earthquakes and of explosions. We developed a linear discriminant function (LDF), that, in application to P / S measured at MDJ, is most effective in separating the earthquake and explosion populations. MDJ lacks usable data for the event of interest, but we have obtained regional data from stations of the nearby Dongbei Broadband Seismographic Network (DBSN), for the event of 12 May 2010 and for nearby underground nuclear tests conducted in 2006 and 2009. When our LDF is applied to DBSN data, and to data from stations SMT and NE3C in China, the LDF values measured from P/S ratios from known explosions are explosion-like; but for the event of 12 May 2010 the LDF values are earthquake-like for frequencies between 6 and 12 Hz. Furthermore, our method for characterizing earthquakes and explosions on the basis of their regional signals can be widely applied. Measurements of P / S based upon three-component waveform data provide better discrimination power than do those based upon vertical-component data alone.

58 GEOSCIENCES↗
DOE OSTI2026

Reply to “Comment on ‘The Reduced Detection Rate of Signals That Are Hidden by Earthquakes: Case Studies with Spotlight Detectors That Operate at Seismic Arrays,’ by Joshua D. Carmichael, Brent G. Delbridge, and Richard Alfaro-Diaz” by Paul G. Richards

We reply to a comment that Paul G. Richards (Richards, 2026) directed to an article by Carmichael et al. (2025). Richards expressed concern over two issues. The first issue relates to the size of the explosions discussed in the article. The second relates to the probability that earthquakes and explosions sourced near the same location coincide in time, by chance. We do not address the first issue because the original article does not assign significance to the size of the explosions from the point of view of an experimental party. We do respond to Richards’ comment on the second issue and claim that it can be explained through a clarification about conditional versus joint probabilities. Our present discussion, therefore, describes the difference between the conditional probability that a correlator fails, given that an explosion and earthquake coincidently occur in the same place, and the joint probability that a correlator fails while an earthquake and explosion also coincidentally occur in the same place. This latter, joint probability appears to be rare. We clarify that our original article did not treat the joint probability, only the conditional probability.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2014

The seismic noise environment of Antarctica

Seismographic coverage of Antarctica prior to 2007 consisted overwhelmingly of a handful of long running and sporadically deployed transient stations, many of which were principally collocated with scientific research stations. Thus, despite very cold temperatures, sunless winters, challenging logistics, and extreme storms, recent developments in polar instrumentation driven by new scientific objectives have opened up the entirety of Antarctica to year–round and continuous seismological observation (e.g., Nyblade et al., 2012).

58 GEOSCIENCES↗
DOE OSTI2018

Absolute Locations of the North Korean Nuclear Tests Based on Differential Seismic Arrival Times and InSAR

Absolute location of the announced Democratic People’s Republic of Korea (DPRK) nuclear test on 6 January 2016 is constrained by fitting associated, Interferometric Synthetic Aperture Radar (InSAR)-based ground displacement with elastic finite-element modeling of an underground explosion source, including the effects of topography. The other five announced nuclear tests are located using arrival times and differential arrival times of regional and teleseismic body waves and constraints on the 6 January 2016 event location. Nuclear tests on 6 January 2016, 9 September 2016, and 3 September 2017 are under the summit ridge of Mt. Mantap, and tests on 25 May 2009 and 12 February 2013 are south of the topographic crest under the steep southern face of the mountain. The first test on 9 October 2006 was located near the crest of a separate topographic ridge approximately 2.87 km east of the 6 January 2016 event. Several unannounced events have occurred in the vicinity of the test site. The location uncertainty ellipse of an event approximately 8 min 30 s after the 2017 announced test covers the DPRK test site and is likely to have occurred there. Finally, additional events on 27 September 2017 and 12 October 2017 are 4–8 km northwest of the test site, and location probability regions do not overlap the test site.

58 GEOSCIENCES↗
DOE OSTI2020

Rescuing Legacy Seismic Data FAIR’ly

The Earth’s interconnected and dynamical systems operate on a spectrum of time scales from millions of years to fractions of a second. While the evolution of the Earth and its deep interior are beyond the time span of human observations, understanding of many natural phenomena operating on human times scales have benefited from direct scientific observation. Continuous processes and those that are repeated over time shape the environment we live in. Furthermore, as we are faced with unprecedented changes to climate, understanding the deeper patterns and trends in natural systems through time have taken on new importance (Research Data Alliance, 2019). The call to reuse data is driven not only by economics but also by the recognition of their complete uniqueness (observations of natural systems are not repeatable) and scientific value in enhancing current understandings as well as potential new discoveries especially in the era of big data. These data are part of the historical record and our scientific heritage (American Geophysical Union, 2019) not only in explicitly recording earth observations but implicitly recording, and thus providing the evidence that addresses the manner in which science was conducted.

58 GEOSCIENCES↗