Zack Spica

University of Michigan–Ann Arbor

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Mathieu Perton

Universidad Nacional Autónoma de México

Loïc Viens

Los Alamos National Laboratory

D. Legrand

Universidad Nacional Autónoma de México

Masanao Shinohara

Association for the Development of Earthquake Prediction

Kiwamu Nishida

The University of Tokyo

Gregory C. Beroza

Stanford University

Tomoaki Yamada

The University of Tokyo

Beatriz Gaite

Instituto Geográfico Nacional

Biondo Biondi

Stanford University

A. Iglesias

Universidad Nacional Autónoma de México

Cooperative Institutions

Universidad Nacional Autónoma de México

Stanford University

California Institute of Technology

United States Geological Survey

The University of Tokyo

Centre National de la Recherche Scientifique

Planetary Science Institute

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

University of Bristol

University of Alaska Fairbanks

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Bend Faulting at the Edge of a Flat Slab: The 2017 M_w7.1 Puebla‐Morelos, Mexico Earthquake

Geophysical Research Letters (2018)

Diego Melgar Xyoli Pérez‐Campos L. Ramirez‐Guzman Zack Spica Víctor H. Espíndola

Abstract We present results of a slip model from joint inversion of strong motion and static Global Positioning System data for the M w 7.1 Puebla‐Morelos earthquake. We find that the earthquake nucleates at the bottom of the oceanic crust or within the oceanic mantle with most of the moment release occurring within the oceanic mantle. Given its location at the edge of the flat slab, the earthquake is likely the result of bending stresses occurring at the transition from flat slab subduction to steeply dipping subduction. The event strikes obliquely to the slab, we find a good agreement between the seafloor fabric offshore the source region and the strike of the earthquake. We argue that the event likely reactivated a fault first created during seafloor formation. We hypothesize that large bending‐related events at the edge of the flat slab are more likely in areas of low misalignment between the seafloor fabric and the slab strike where reactivation of preexisting structures is favored. This hypothesis predicts decreased likelihood of bending‐related events northwest of the 2017 source region but also suggests that they should be more likely southeast of the 2017 source region.

Slab

Seafloor Spreading

Slab window

10.1002/2017gl076895

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Velocity analysis and moveout-based event detection using downhole DAS records

Ariel Lellouch Siyuan Yuan Zack Spica Biondo Biondi William L. Ellsworth

We show how vertical downhole distributed acoustic sensing arrays can be used for P- and S- velocity analysis along the array. Using such velocity models, the array can be used in an effective moveout-based earthquake detection approach. We demonstrate both applications on 20 days of passive records at the San Andreas Fault Observatory at Depth, which comprises of a ∼800 m deep vertical array. Estimated P velocities are comparable to an active geophone survey and S velocities are extracted for the first time in the area. Over 75% of the events in the USGS catalog in the area are detected, as well as a new earthquake. Presentation Date: Tuesday, September 17, 2019 Session Start Time: 1:50 PM Presentation Time: 3:55 PM Location: 221C Presentation Type: Oral

10.1190/segam2019-3214849.1

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Locating the Precise Sources of High‐Frequency Microseisms Using Distributed Acoustic Sensing

Geophysical Research Letters (2022)

Han Xiao Toshiro Tanimoto Zack Spica Beatriz Gaite Sandra Ruiz‐Barajas

Abstract Although microseisms have been observed for more than 100 years, the precise locations of their excitation sources in the oceans are still elusive. Underwater Distributed Acoustic Sensing (DAS) brings new opportunities to study microseism generation mechanisms. Using DAS data off the coast of Valencia, Spain, and applying a cross‐correlation approach, we show that the sources of high‐frequency microseisms (0.5–2 Hz) are confined between 7 and 27 km from the shore, where the water depth varies from 25 to 100 m. Over time, we observe that these sources move quickly along narrow areas, sometimes within a few kilometers. Our methodology applied to DAS data allows us to characterize microseisms with a high spatiotemporal resolution, providing a new way of understanding these global and complex seismic phenomena happening in the oceans.

Microseism

10.1029/2022gl099292

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Transition of the Slab Geometry at the Eastern End of the Trans-Mexican Volcanic Belt from Ambient Noise and Earthquake Surface Waves

AGU Fall Meeting Abstracts (2016)

J. Castillo R. W. Clayton Zack Spica Xyoli Pérez‐Campos

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Earthquake Magnitude With DAS: A Transferable Data‐Based Scaling Relation

Geophysical Research Letters (2023)

Jiuxun Yin Weiqiang Zhu Jiaxuan Li Ettore Biondi Yaolin Miao

Abstract Distributed Acoustic Sensing (DAS) is a promising technique to improve the rapid detection and characterization of earthquakes. Previous DAS studies mainly focus on the phase information but less on the amplitude information. In this study, we compile earthquake data from two DAS arrays in California, USA, and one submarine array in Sanriku, Japan. We develop a data‐driven method to obtain the first scaling relation between DAS amplitude and earthquake magnitude. Our results reveal that the earthquake amplitudes recorded by DAS in different regions follow a similar scaling relation. The scaling relation can provide a rapid earthquake magnitude estimation and effectively avoid uncertainties caused by the conversion to ground motions. Our results show that the scaling relation appears transferable to new regions with calibrations. The scaling relation highlights the great potential of DAS in earthquake source characterization and early warning.

10.1029/2023gl103045

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A Moveout-Based Method for the Detection of Weak Seismic Events Using Downhole DAS Arrays

81st EAGE Conference and Exhibition 2019 (2019)

Ariel Lellouch Songyong Yuan Zack Spica Biondo Biondi W. L. Ellsworth

Summary Distributed acoustic sensing offers the possibility of high-resolution passive monitoring of seismic events. Local coherency of the recorded wavefields allows for array-based processing techniques. In this study, we apply such techniques in a downhole array at the San Andreas Fault Observatory at Depth. We begin by estimating the seismic velocity along the well using both earthquake records and ambient noise interferometry. Results are compared to a conventional near-offset VSP geophone survey. DAS earthquake records also allow for S-wave velocity estimation. We utilize the computed velocity in a moveout-based detection algorithm. The method takes into account velocity along the array as well as the range of possible incidence angles of incoming events. We apply it to 20 days of data, recorded in June-July 2017. Above 70% of catalogued events in the area are detected, and a new, weak, uncatalogued event is discovered. These results set the path for DAS monitoring of natural and induced events.

Geophone

Seismic interferometry

Seismic array

Slowness

Seismic velocity

Vertical seismic profile

Data set

10.3997/2214-4609.201901242

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Tomografía de Velocidad de Grupo de Ondas de Rayleigh para el Oriente de México y el Istmo de Tehuantepec

Boletín de la Sociedad Geológica Mexicana (2014)

Francisco Córdoba Montiel Arturo Iglesias Mendoza S. K. Singh Zack Spica D. Legrand

En este trabajo se utilizaron registros de ruido sísmico de la red permanente de banda ancha del

10.18268/bsgm2014v66n3a3

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Urban Seismic Site Characterization by Fiber‐Optic Seismology

Journal of Geophysical Research Solid Earth (2020)

Zack Spica Mathieu Perton Eileen Martin Gregory C. Beroza Biondo Biondi

Abstract Accurate ground motion prediction requires detailed site effect assessment, but in urban areas where such assessments are most important, geotechnical surveys are difficult to perform, limiting their availability. Distributed acoustic sensing (DAS) offers an appealing alternative by repurposing existing fiber‐optic cables, normally employed for telecommunication, as an array of seismic sensors. We present a proof‐of‐concept demonstration by using DAS to produce high‐resolution maps of the shallow subsurface with the Stanford DAS array, California. We describe new methods and their assumptions to assess H/V spectral ratio—a technique widely used to estimate the natural frequency of the soil—and to extract Rayleigh wave dispersion curves from ambient seismic field. These measurements are jointly inverted to provide models of shallow seismic velocities and sediment thicknesses above bedrock in central campus. The good agreement with an independent survey validates the methodology and demonstrates the power of DAS for microzonation.

Bedrock

Rayleigh Wave

10.1029/2019jb018656

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Detection of Earthquake Infragravity and Tsunami Waves With Underwater Distributed Acoustic Sensing

Geophysical Research Letters (2024)

Han Xiao Zack Spica Jiaxuan Li Zhongwen Zhan

Abstract Underwater Distributed Acoustic Sensing (DAS) utilizes optical fiber as a continuous sensor array. It enables high‐resolution data collection over long distances and holds promise to enhance tsunami early warning capabilities. This research focuses on detecting infragravity and tsunami waves associated with earthquakes and understanding their origin and dispersion characteristics through frequency‐wavenumber domain transformations and beamforming techniques. We propose a velocity correction method based on adjusting the apparent channel spacing according to water depth to overcome the challenge of detecting long‐wavelength and long‐period tsunami signals. Experimental results demonstrate the successful retrieval of infragravity and tsunami waves using a subsea optical fiber in offshore Oregon. These findings underscore the potential of DAS technology to complement existing infragravity waves detection systems, enhance preparedness, and improve response efforts in coastal communities. Further research and development in this field are crucial to fully utilize the capabilities of DAS for enhanced tsunami monitoring and warning systems.

Subsea

Microseism

Rayleigh Wave

10.1029/2023gl106767

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Tomography of Rayleigh wave group velocity for Eastern Mexico and the Isthmus of Tehuantepec

Boletín de la Sociedad Geológica Mexicana (2014)

Francisco Córdoba Montiel Arturo Iglesias Mendoza S. K. Singh Zack Spica D. Legrand

En este trabajo se utilizaron registros de ruido sismico de la red permanente de banda ancha del Servicio Sismologico Nacional de Mexico y de las redes temporales de banda ancha MASE y VEOX para calcular las funciones de Green a partir de las correlaciones cruzadas de ruido de la componente vertical entre pares de estaciones. El arreglo MASE (Experimento de Subduccion Mesoamericano) consistio en cien estaciones distribuidas a lo largo de un perfil perpendicular a la trinchera entre Acapulco, Guerrero, y Tempoal, Veracruz, cerca del Golfo de Mexico. Este experimento opero de diciembre de 2004 a mayo de 2007. Cuarenta y seis de estas estaciones se reubicaron en un perfil N-S va desde el Golfo de Mexico hasta la costa del Pacifico, a traves del Istmo de Tehuantepec. Este segundo arreglo de estaciones corrio de julio de 2007 a marzo de 2009 y se le denomino VEOX (Veracruz-Oaxaca). A partir de la funcion de Green extraida de la correlacion cruzada entre cada par de estaciones, se obtuvieron las curvas de dispersion de ondas de Rayleigh, las cuales describen la velocidad de grupo promedio dentro de un intervalo de periodos determinado. Ademas, se utilizaron algunos sismos regionales registrados en estas redes sismicas para obtener curvas de dispersion de ondas superficiales (Rayleigh) y, en consecuencia, la velocidad de grupo promedio entre cada par estacion-epicentro. Este conjunto mezclado de mediciones de velocidad de grupo se invirtio para obtener imagenes tomograficas en periodos discretos (5-50 s). Las pruebas de resolucion muestran que las regiones con mayor cobertura estan en los alrededores de ambos experimentos temporales. Se obtiene un buen modelo de velocidad en un area grande entre ambos experimentos. En los periodos cortos (< 15 s), las imagenes presentan buena correlacion con las caracteristicas geologicas superficiales. Las anomalias de baja velocidad estan relacionadas con

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