A5015371735- earthquake and tectonic studies
- Seismic Waves and Analysis
- Seismology and Earthquake Studies
- High-pressure geophysics and materials
- Seismic Imaging and Inversion Techniques
- Geological and Geochemical Analysis
- Geological and Geophysical Studies
- Earthquake Detection and Analysis
- Geophysical and Geoelectrical Methods
- Reservoir Engineering and Simulation Methods
- Atmospheric and Environmental Gas Dynamics
- Cryospheric studies and observations
- Geochemistry and Geologic Mapping
- Geotechnical and Geomechanical Engineering
- Methane Hydrates and Related Phenomena
- Computational Physics and Python Applications
- Data Quality and Management
- Advanced X-ray and CT Imaging
- Advanced Computational Techniques and Applications
- Meteorological Phenomena and Simulations
- Medical Imaging Techniques and Applications
- Geological Studies and Exploration
- Hydraulic Fracturing and Reservoir Analysis
- Geological and Tectonic Studies in Latin America
- Bayesian Modeling and Causal Inference
United States Geological Survey
2016-2025
Cascades Volcano Observatory
2016-2025
Volcano Science Center
2019-2020
University of Wisconsin–Madison
2008-2014
We have extended the double‐difference seismic tomography method to teleseismic distances with 3‐D ray tracing conducted through nested regional‐global velocity models and applied relocate seismicity from Sumatra‐Andaman region before after great earthquakes of 2004 2005. tested algorithm's accuracy using both independent local data an alternate relocation found good agreement between results. The use depth phases, differential times, a realistic model improves precision epicenters focal...
SUMMARY High seismicity rates in eastern Indonesia occur due to the complex interaction of several tectonic plates which resulted two deadly, destructive earthquake sequences that occurred Lombok Island and city Palu, Sulawesi 2018. The first sequence began July with an Mw 6.4 event near Lombok, culminating 7.0 8 d later. This was then followed by a nearby 6.9 12 Approximately 1000 km northeast, separate weeks later Palu where 7.5 triggered tsunami. In this study, we present hypocentre...
We present a new tomographic model of the mantle in area 2010 M8.8 Maule earthquake and surrounding regions. Increased ray coverage provided by aftershock data allows us to image detailed subducting slab structure mantle, from region flat subduction north rupture overlapping between 1960 M9.5 events south. have combined teleseismic primary depth phase arrivals with available local better constrain locations region, which we use conduct nested regional–global tomography. The reveals its...
After 53 years of quiescence, Mount Agung awoke in August 2017, with intense seismicity, measurable ground deformation, and thermal anomalies the summit crater. Although seismic unrest peaked late September early October, volcano did not start erupting until 21 November. The most explosive eruptions accompanying rapid lava effusion occurred between 25 29 Smaller infrequent explosions extrusions continue through present (June 2019). delay eruption caused considerable challenges to emergency...
Taking advantage of the increased ray coverage due to seismicity following 2004 December and 2005 March great earthquakes, an improved iterative regional–global tomographic method was applied Sumatra–Andaman adjacent regions better constrain 3-D mantle velocity heterogeneity in region. Velocity hypocentral parameters were iteratively perturbed sharpen image subducted slab. Several iterations performed, effects source mislocation considered process, issue usually neglected global tomography....
New data provided by the 2004–2005 Sumatra‐Andaman great earthquake sequences allow us to image with improved detail P ‐wave velocity structure beneath Sumatra and adjacent regions. Below northern Sumatra, we find that slab is folded at depth, exhibiting geometry similar of volcanic arc trench surface. We speculate this fold plays a major role in segmentation megathrust, may impede rupture propagation region. North significant material mantle transition zone imaged for first time, infer...
Abstract A moderate‐magnitude earthquake swarm occurred in the remote Izu Islands region of Japan between October 1 and 8, 2023. The included 151 shallow earthquakes cataloged by U.S. Geological Survey, which notably a roughly 2.5‐hr episode 15 successive magnitude ( M ) < 5.5 earthquakes. Origin times were coincident with regionally recorded tsunami waves, but tsunamigenesis for is uncommon, indicating that volcanic activity generated ocean displacements. Leveraging surface‐wave relative...
Abstract Detailed P-wave speed velocity structure beneath the Sunda arc has been successfully imaged by applying a non-linear approach to seismic tomography. Nearly one million compressional phases from events within Indonesian region have used. These include surface-reflected depth pP and pwP in order improve sampling of upper-mantle structure, particularly below back-arc regions. We combined high-resolution regional inversion with low-resolution global minimize mapping distant aspherical...
We present location results for a group of [Formula: see text] microearthquakes that occurred in 2012 region Oklahoma hosting ongoing exploration activities. Using local passive surface seismic monitoring network 15 broadband stations, we applied two modern techniques use fundamentally different approaches. The first is pick-based double-difference relocation method with waveform crosscorrelation. Multiple-event such as these are generally regarded the best approach obtaining high-precision...
Research Article| January 03, 2018 Hypocenter Relocation along the Sunda Arc in Indonesia, Using a 3D Seismic‐Velocity Model Andri D. Nugraha; Nugraha aGlobal Geophysics Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jl. Ganesa 10, West Java 40132, nugraha@gf.itb.ac.id Search for other works by this author on: GSW Google Scholar Hasbi A. Shiddiqi; Shiddiqi bEarth Sciences Graduate Program, Earth Technology, Indonesia Sri Widiyantoro; Widiyantoro Clifford H....
Seismic rate increases often precede eruptions at volcanoes worldwide. However, many occur without such precursors, limiting their usefulness for forecasting in some cases. Additionally, identifying seismic near with high levels of background seismicity is non-trivial and periods elevated ensuing eruptions. Although these issues are commonly known, efforts to quantify them limited. In this study, we consistently apply a common statistical tool, the -statistic, seismically monitored Alaska...
Abstract The earthquake swarm accompanying the January 2022 Hunga Tonga-Hunga Ha'apai (HTHH) volcanic eruption includes a large number of posteruptive moderate-magnitude seismic events and presents unique opportunity to use remote monitoring methods characterize compare activity with other historical caldera-forming eruptions. We compute improved epicentroid locations, magnitudes, regional moment tensors from this using teleseismic surface-wave cross correlation waveform modeling. Precise...
Sabancaya volcano is the youngest and second most active in Peru. It part of Ampato-Sabancaya volcanic complex which sits to south ancient Hualca several frequently faults, thus resulting volcano-tectonic interactions. After 15 years repose, 2013, a series 4 earthquakes with magnitude >4.5 occurred within 24 h, marking beginning new episode unrest. Several additional swarms following until magmatic eruptive activity started on 6 November 2016. This ongoing as this writing, an average 50...
Volcanic earthquake catalogs are an essential data product used to interpret subsurface volcanic activity and forecast eruptions. Advances in detection techniques (e.g., matched-filtering, machine learning) relative relocation tools have improved catalog completeness refined event locations. However, most volcano observatories yet incorporate these into their catalog-building workflows. This is due part complexities operationalizing, automating, calibrating a satisfactory way for disparate...
We have determined source mechanisms for nine high-quality microseismic events induced during hydraulic fracturing of the Montney Shale in Canada. Seismic data were recorded using a dense regularly spaced grid sensors at surface. The design and geometry survey are such that P-wave amplitudes essentially map upper focal hemisphere, allowing mechanism to be interpreted directly from data. Given inherent difficulties computing reliable moment tensors (MTs) high-frequency data, surface amplitude...
Efforts to determine general moment tensors (MTs) for microearthquakes in volcanic areas are often hampered by small seismic networks, which can lead poorly constrained hypocentres and inadequate modelling of velocity heterogeneity. In addition, noisy signals make it difficult identify phase arrivals correctly magnitude events. However, earthquakes have source mechanisms that deviate from brittle double-couple shear failure due magmatic and/or hydrothermal processes. Thus, determining...
Abstract Magma intrusion rate is a key parameter in eruption triggering but poorly quantified existing geodetic studies. Here we examine two episodes of rapid inflation this context. Two noneruptive microseismic swarms were recorded at Semisopochnoi Volcano, Alaska 2014–2015. We use differential SAR techniques and TerraSAR‐X images to document surface deformation from 2011 2015, which comprises island‐wide radial totaling ~25 cm (+/−1 cm) line sight displacement Multiple source geometries...
Abstract Waveform cross-correlation with bispectrum verification is combined double-difference tomography to increase the precision of earthquake locations and constrain regional 3D P -wave velocity heterogeneity at Great Sitkin volcano, Alaska. From 1999 through 2005, Alaska Volcano Observatory (AVO) recorded ∼1700 earthquakes in vicinity Sitkin, including two M L 4.3 that are among largest events AVO catalog. The majority occurred during 2002 formed temporally spatially separate event...
Abstract A three‐dimensional (3‐D), high‐resolution P wave seismic attenuation model for the New Madrid Seismic Zone (NMSZ) is determined using path ( t *) values of small‐magnitude earthquakes M D < 3.9). Events were recorded at 89 broadband and short‐period seismometers Cooperative Network 40 Portable Array Numerical Data Acquisition experiment. The amplitude spectra all are simultaneously inverted source, *), site parameters. * Q local earthquake tomography methods a known 3‐D velocity...
Brief Report| February 04, 2014 Multiscale Seismic Tomography and Earthquake Relocation Incorporating Differential Time Data: Application to the Maule Subduction Zone, Chile Jeremy D. Pesicek; Pesicek aUniversity of Wisconsin–Madison, Department Geoscience, 1215 W Dayton Street, Madison, Wisconsin 53706 *Now at Spectraseis Inc., 1899 Wynkoop Suite 350, Denver, Colorado 80202. Search for other works by this author on: GSW Google Scholar Haijiang Zhang; Zhang bLaboratory Seismology Physics...
Abstract Seismic velocity models of the crust are an integral part earthquake monitoring systems at volcanoes. 1D that vary only in depth typically used for real-time hypocenter determination and serve as critical reference detailed 3D imaging studies geomechanical modeling. Such usually computed using seismic tomographic methods rely on P- S-wave arrival-time picks from numerous earthquakes recorded receivers around volcano. Traditional linearized jointly invert source locations, structure,...
Seismic tomography with a non-linear approach has been successfully applied to image the P-wave velocity structure beneath Banda arc in detail. Nearly one million compressional phases including surfacereflected depth pP and pwP from events within Indonesian region have used. The incorporated order improve sampling of uppermantle structure, particularly below Sea back-arc regions. For model parameterization, we combined highresolution regional inversion low-resolution global allow detailed...
Abstract Determining whether seismicity near volcanoes is due primarily to tectonic or magmatic processes a challenging but critical endeavor for volcanic eruption forecasting and detection, especially at poorly monitored volcanoes. Global statistics on the occurrence timing of earthquakes both within outside eruptive periods reveal patterns in that may improve our ability discern magmatically driven from purely seismicity. In this paper, we catalog magnitude four greater (M4+) globally...