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  1. Article: Crustal Seismic Attenuation of the Central United States and Intermountain West

    Levandowski, Will / Boyd, Oliver Salz / AbdelHameid, Danya / McNamara, Daniel Edward

    Journal of geophysical research. 2021 Dec., v. 126, no. 12

    2021  

    Abstract: Seismic attenuation is generally greater in the western United States (WUS) than the central and eastern United States (CEUS), but the nature of this transition or location of this boundary is poorly constrained. We conduct crustal seismic (Lg) ... ...

    Abstract Seismic attenuation is generally greater in the western United States (WUS) than the central and eastern United States (CEUS), but the nature of this transition or location of this boundary is poorly constrained. We conduct crustal seismic (Lg) attenuation tomography across a region that stretches from the CEUS across the Rocky Mountains to the Basin and Range using a total of 115,870 amplitude measurements from 106 earthquakes recorded on 544 stations across five frequency bands spanning 0.5–16 Hz. Similar to previous studies, we find higher attenuation in the WUS (Q₀ ∼ 190) than the nominally CEUS (Q₀ ∼ 250) and comparatively high attenuation on the Gulf Coast (Q₀ ∼ 175). Our models defy simple east versus west regionalization, however. Heterogeneity within the Rocky Mountain region—low attenuation in the Colorado Plateau interior and Wyoming Craton (Q₀ ∼ 230) compared to high attenuation in the southern Rockies (Q₀ ∼ 110)—exceeds the gross differences between the CEUS and western United States. These province‐scale patterns are readily interpreted in terms of intrinsic attenuation. The boundary between the Colorado Plateau and Basin and Range hosts the highest attenuation imaged in the study area (Q₀ ∼ 90), consistent with localized scattering across contrasting crustal structure. Focused high attenuation in the southern Rockies may represent the effects of represent in situ partial crustal melt. Within the CEUS, second‐order bands of comparatively high attenuation align with the Proterozoic Yavapai‐Mazatzal suture zone and Midcontinent Rift. This complex attenuation structure defies broad regionalization and suggests a need for path‐specific models near these boundaries and for critical infrastructure.
    Keywords Proterozoic eon ; basins ; coasts ; geophysics ; infrastructure ; plateaus ; research ; tomography ; Intermountain West region ; Rocky Mountain region ; Wyoming
    Language English
    Dates of publication 2021-12
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ISSN 2169-9313
    DOI 10.1029/2021JB022097
    Database NAL-Catalogue (AGRICOLA)

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  2. Article ; Online: Gravitational body forces focus North American intraplate earthquakes.

    Levandowski, Will / Zellman, Mark / Briggs, Rich

    Nature communications

    2017  Volume 8, Page(s) 14314

    Abstract: Earthquakes far from tectonic plate boundaries generally exploit ancient faults, but not all intraplate faults are equally active. The North American Great Plains exemplify such intraplate earthquake localization, with both natural and induced seismicity ...

    Abstract Earthquakes far from tectonic plate boundaries generally exploit ancient faults, but not all intraplate faults are equally active. The North American Great Plains exemplify such intraplate earthquake localization, with both natural and induced seismicity generally clustered in discrete zones. Here we use seismic velocity, gravity and topography to generate a 3D lithospheric density model of the region; subsequent finite-element modelling shows that seismicity focuses in regions of high-gravity-derived deviatoric stress. Furthermore, predicted principal stress directions generally align with those observed independently in earthquake moment tensors and borehole breakouts. Body forces therefore appear to control the state of stress and thus the location and style of intraplate earthquakes in the central United States with no influence from mantle convection or crustal weakness necessary. These results show that mapping where gravitational body forces encourage seismicity is crucial to understanding and appraising intraplate seismic hazard.
    Language English
    Publishing date 2017-02-17
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 2041-1723
    ISSN (online) 2041-1723
    DOI 10.1038/ncomms14314
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Gravitational body forces focus North American intraplate earthquakes

    Will Levandowski / Mark Zellman / Rich Briggs

    Nature Communications, Vol 8, Iss 1, Pp 1-

    2017  Volume 9

    Abstract: Intraplate earthquakes occur far from tectonic plate boundaries and so it is vital to understand how and where they may happen. Here, Levandowskiet al. create a 3D density map of the North America Great Plains showing that gravitational forces play a ... ...

    Abstract Intraplate earthquakes occur far from tectonic plate boundaries and so it is vital to understand how and where they may happen. Here, Levandowskiet al. create a 3D density map of the North America Great Plains showing that gravitational forces play a controlling role in intraplate earthquake locations.
    Keywords Science ; Q
    Language English
    Publishing date 2017-02-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article: A 3D Full Stress Tensor Model for Oklahoma

    Chai, Chengping / Delorey, Andrew A. / Maceira, Monica / Levandowski, Will / Guyer, Robert A. / Zhang, Haijiang / Coblentz, David / Johnson, Paul A.

    Journal of geophysical research. 2021 Apr., v. 126, no. 4

    2021  

    Abstract: The stress tensor is an important property for upper crustal studies such as those that involve pore fluids and earthquake hazards. At tectonic plate scale, plate boundary forces and mantle convection are the primary drivers of the stress field. In many ... ...

    Abstract The stress tensor is an important property for upper crustal studies such as those that involve pore fluids and earthquake hazards. At tectonic plate scale, plate boundary forces and mantle convection are the primary drivers of the stress field. In many local settings (10–100 s of km and <10 km depth) in tectonic plate interiors, we can simplify by assuming a constant background stress field that is perturbed by local heterogeneity in density and elasticity. Local stress orientation and sometimes magnitude can be estimated from earthquake and borehole‐based observations when available. Modeling of the local stress field often involves interpolating sparse observations. We present a new method to estimate the 3D stress field in the upper crust and demonstrate it for Oklahoma. We created a 3D material model by inverting multiple types of geophysical observations simultaneously. Integrating surface‐wave dispersion, local travel times and gravity observations produces a model of P‐wave velocity, S‐wave velocity, and density. The stress field can then be modeled using finite element simulations. The simulations are performed using our simplified view of the local stress field as the sum of a constant background stress field that is perturbed by local density and elasticity heterogeneity and gravitational body forces. An orientation of N82°E, for the maximum compressive tectonic force, best agrees with previously observed stress orientations and faulting types in Oklahoma. The gravitational contribution of the horizontal stress field has a magnitude comparable to the tectonic contribution for the upper 5 km of the subsurface.
    Keywords convection ; earthquakes ; finite element analysis ; geophysics ; gravity ; models ; research ; tectonics ; Oklahoma
    Language English
    Dates of publication 2021-04
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ISSN 2169-9313
    DOI 10.1029/2020JB021113
    Database NAL-Catalogue (AGRICOLA)

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