A5084946489- Seismology and Earthquake Studies
- earthquake and tectonic studies
- Seismic Imaging and Inversion Techniques
- Seismic Waves and Analysis
- High-pressure geophysics and materials
- Geological and Geochemical Analysis
- Earthquake Detection and Analysis
- Anomaly Detection Techniques and Applications
- Geophysical Methods and Applications
- Time Series Analysis and Forecasting
- Fault Detection and Control Systems
- Geological and Geophysical Studies
- Image and Signal Denoising Methods
- Reservoir Engineering and Simulation Methods
- Hydraulic Fracturing and Reservoir Analysis
- Drilling and Well Engineering
- Neural Networks and Applications
- Geophysics and Sensor Technology
- Geochemistry and Geologic Mapping
- Scientific Computing and Data Management
- Advanced Computational Techniques and Applications
- Software System Performance and Reliability
- Advanced Database Systems and Queries
- Speech and Audio Processing
- Data Management and Algorithms
Sandia National Laboratories
2018-2025
Sandia National Laboratories California
2017-2022
University of Washington
2012
Washington University in St. Louis
2003-2005
GFZ Helmholtz Centre for Geosciences
1999-2003
We derive the rupture history of 1999 August 17 Izmit (Mw=7.4) and November 12 Düzce (Mw=7.1) earthquakes in Turkey from teleseismic body waves using broad‐band data Global Seismograph Network, aftershock locations mapped surface breaks. The centroid solutions indicate strike‐slip mechanisms for both events. earthquake was characterized by propagating predominantly eastwards. It consisted a main lasting about 25 s followed within 1 min two more events Mw=6.9 Mw=7.0. With data, we could not...
The thickness of the mantle transition zone beneath Cameroon has been mapped using data from 2005-2007 Broadband Seismic Experiment to evaluate models for origin Volcanic Line (CVL). Some 2200 receiver functions have stacked a 3-D velocity model, revealing Ps conversions discontinuities at depths ~410 and 660 km. Results yield nearly uniform (251 ± 10 km) that is similar global average, implying any thermal anomalies in upper CVL do not extend as deep zone. This finding, when combined with...
Abstract The Cameroon Volcanic Line (CVL) is a 1800 km long volcanic chain, extending SW‐NE from the Gulf of Guinea into Central Africa, that lacks typical age progression exhibited by hot spot‐related tracks. This study investigates upper mantle seismic structure beneath CVL and surrounding regions to constrain origin lines are poorly described classic plume model. Rayleigh wave phase velocities measured at periods 20 182 s following two‐plane methodology, using data Seismic Experiment,...
ABSTRACT Seismic waveform data are generally contaminated by noise from various sources. Suppressing this effectively so that the remaining signal of interest can be successfully exploited remains a fundamental problem for seismological community. To date, most common suppression methods have been based on frequency filtering. These methods, however, less effective when and share similar bands. Inspired source separation studies in field music information retrieval (Jansson et al., 2017)...
ABSTRACT Recorded seismic data are generally contaminated by noise from different sources, which masks the signals of interest. In seismology community, frequency filtering (FF) is standard method for suppression. However, when signal interest and share same band, latter cannot be filtered out without infringing on former. We implemented a suppression approach based mathematical morphology theorem. The involves compound operations dilation erosion using structuring elements varying lengths...
Abstract The discrimination problem in seismology aims to accurately classify different underground source types based on local, regional, and/or teleseismic observations of ground motion. Typical discriminant approaches are rooted fundamental, physics-based differences radiation pattern or wave excitation, which can be frequency-dependent and may not make use the full waveform. In this article, we explore whether phase amplitude distances derived from dynamic time warping (DTW) elastic...
Seismic imaging of subduction zones can provide constraints on mineral reactions in the slab and surrounding regions. We use P ‐to‐ S converted phases from teleseisms recorded at broadband stations Mariana Islands to image forearc arc regions convergent margin. The subducting oceanic crust is observed between 75 110 km depth as a thin low velocity zone overlying Moho, demonstrating that basalt eclogite phase transition must occur greater depth. A (LVZ), approximately 10−25 thick, whose upper...
The Cameroon Volcanic Line (CVL) is an 1800-km-long line of Cenozoic volcanoes that does not show a chronological progression consistent with hotspot-related volcanism. We investigate seismic anisotropy to determine the upper-mantle lattice preferred orientation and constrain mantle flow pattern using temporary array 32 broad-band seismographs deployed throughout between 2005 2007 along two additional permanent in adjacent countries. fast direction lag time beneath each station by stacking...
Abstract The capability to discriminate low‐magnitude earthquakes from low‐yield anthropogenic sources, both detectable only at local distances, is of increasing interest the event monitoring community. We used a dataset seismic events in Utah recorded during 14‐day period (1–14 January 2011) by University Seismic Stations network perform comparative study classification scale using amplitude ratio (AR) methods and machine learning (ML) approach. catalog consists 7377 with magnitudes MC...
ABSTRACT Determining the depths of small crustal earthquakes is challenging in many regions world, because most seismic networks are too sparse to resolve trade-offs between depth and origin time with conventional arrival-time methods. Precise accurate estimation important, it can help seismologists discriminate explosions, which relevant monitoring nuclear test ban treaties producing earthquake catalogs that uncontaminated by mining blasts. Here, we examine sensitivity several physics-based...
Source parameters for eight large deep earthquakes are inferred from broadband data of the Global Seismograph Network. We completed an unprecedented set composed 14 largest ( M w ranging 7.0 to 8.3) six different subduction zones studied with identical source parameter inversion methods. The study confirms earlier findings that earthquake properties vary temperature subducting plate. Events in cold slabs show high aftershock activity, rupture velocity, and seismic efficiency. In contrast,...
Research Article| March 20, 2018 Depth Discrimination Using Rg‐to‐Sg Spectral Amplitude Ratios for Seismic Events in Utah Recorded at Local Distances Rigobert Tibi; Tibi aSandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185‐0404, rtibi@sandia.gov Search other works by this author on: GSW Google Scholar Keith D. Koper; Koper bDepartment of Geology and Geophysics, University Utah, 115 South 1460 East, Salt Lake City, 84112 Kristine L. Pankow; Pankow Christopher J. Young...
Recordings of deep Tonga earthquakes from two arrays 12 broadband seismographs each in the Fiji and islands are stacked searched for reflections conversions upper mantle discontinuities subduction zone. The operated as part Seismic Arrays (SAFT) experiment July 2001 to August 2002. In comparison with commonly used teleseismic approaches, short path lengths local data provide smaller Fresnel zones high‐frequency content precise mapping discontinuity topography sharpness. To enhance...
ABSTRACT Seismic waveform data are generally contaminated by noise from various sources, which interfere with the signals of interest. In this study, we implemented and applied several suppression methods using recorded regional network University Utah Seismograph stations. The denoising methods, consisting approaches based on nonlinear thresholding continuous wavelet transforms (CWTs, e.g., Langston Mousavi, 2019), convolutional neural (CNN) (Tibi et al., 2021), frequency filtering, were...
Source parameters of six large earthquakes (7.1 ≤ M w 7.7) in the depth range between 112 and 277 km from five different subduction zones are derived teleseismic body waves recorded by global seismic networks. Except for 21 October 1995 Mexican event, which is consistent with model simple rupture on a planar surface, investigated show complex processes that can be explained irregularities focal region as case shallow events. The inferred velocity moment release varies 2.5 4 km/s,...
We use P ‐to‐ S converted phases from teleseimic data recorded at island and ocean bottom stations in Mariana to investigate the upper mantle structure region. find evidence for double seismic discontinuities base of transition zone near slab. A shallower discontinuity is imaged depths ∼650–715 km a deeper interface lies ∼740–770 depth. The large lateral extent constant both features consistent with horizontal interfaces rather than small‐scale scatterers. amplitude ratios signals suggest...
Source parameters of the 1996 Flores Sea and 1994 Fiji–Tonga deep earthquakes are derived from teleseismic body waves recorded by global seismic network broad-band seismograph stations. Both events consisted several subevents. Models to approximate spatial temporal extent source process include point sources, propagating sources a combination these. For event, rupture lasted about 23 s terminated some 70 km east nucleation as inferred duration P-wave pulses, in agreement with findings...
ABSTRACT Seismic waveform data recorded at stations can be thought of as a superposition the signal from source interest and noise other sources. Frequency-based filtering methods for denoising do not result in desired outcomes when targeted occupy similar frequency bands. Recently, techniques based on deep-learning convolutional neural networks (CNNs), which is decomposed into components, have led to improved results. These CNN methods, use short-time Fourier transform representations time...
Abstract Two events of magnitude (mb) 3.6–3.8 occurred in southern North Korea (NK) on 27 June 2019 and 11 May 2020. Although these were located ∼330–400 km from the known nuclear test site, fact that they within territory NK, a country with recent history underground tests, made them interest for monitoring community. We used P/Lg ratios regional stations to categorize seismic NK 2006 2020, including two events, six declared cavity collapse triggered earthquakes followed 3 September 2017...
Research Article| July 24, 2018 Discrimination of Anthropogenic Events and Tectonic Earthquakes in Utah Using a Quadratic Discriminant Function Approach with Local Distance Amplitude Ratios Rigobert Tibi; Tibi aSandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185‐0404, rtibi@sandia.gov Search for other works by this author on: GSW Google Scholar Keith D. Koper; Koper bDepartment Geology Geophysics, University Utah, 115 South 1460 East, Salt Lake City, 84112 Kristine L....
High frequency records of deep Mariana earthquakes from a dense array ocean bottom seismographs deployed in the arc and back‐arc regions are stacked searched for phases P 660 p S to constrain depth 660‐km discontinuity near slab. Results high‐resolution study suggest that around 18°N lies at about 710–730 km (±14 km) within or vicinity slab core. In region seismicity ceases ∼620 depth. This implies that, although tomographic images show penetrating into lower mantle, terminates ∼100 above...
Abstract The matched filtering technique that uses the cross correlation of a waveform interest with archived signals from template library has proven to be powerful tool for detecting events in regions repeating seismicity. However, is computationally expensive and therefore impractical large sets unless dedicated distributed computing hardware software are used. In this study, we introduce an approximate nearest neighbor (ANN) approach enables use very libraries correlation. Our method...
ABSTRACT The Redmond Salt Mine (RSM) Monitoring Experiment in Utah was designed to record seismoacoustic data at distances less than 50 km for algorithm testing and development. During the experiment from October 2017 July 2019, six broadband seismic stations were operating a time, with three of them having fixed locations duration, whereas other moved different every one-and-half two-and-half months. RSM operations consist nighttime underground blasting several times per week. is located...