The Utility of Geopotential Field Data in Seismotectonic Studies in the Eastern United States

1988 ◽  
Vol 59 (4) ◽  
pp. 289-297 ◽  
Author(s):  
William J. Hinze ◽  
Thomas G. Hildenbrand
Keyword(s):  
United States ◽  
Magnetic Anomaly ◽  
Spatial Relationship ◽  
Gravity Anomalies ◽  
Three Dimensions ◽  
Hazard Evaluation ◽  
Earthquake Activity ◽  
Seismic Zone ◽  
Eastern United States ◽  
Isostatic Gravity

Abstract The deterministic approach to seismic hazard evaluation utilizes all available geologic/geophysical information to map the structure and nature of the crust in three dimensions that may relate to earthquake activity. However, information on the crystalline crust of the eastern United States from direct observations, drilling and sparse crustal seismic studies is limited. In contrast, regional gravity and magnetic anomaly data exist over the entire eastern United States and are available in a digital grid to facilitate processing and analysis. Although these data have serious limitations for detailed interpretation, they can be used to estimate the strength of the crust and the lithosphere and to map and characterize (1) zones of weakness such as paleorifts, sutures, and faults; (2) regions of potential stress amplifications such as plutons and irregularities in fault zones; and (3) basement terranes of generally consistent structural pattern that may delimit coherent regional seismic zones. Free-air, Bouguer, and isostatic gravity anomalies have different applications in the characterization of the crust for seismogenic purposes and complement magnetic anomaly maps which focus on upper crustal features. In concert, these data have provided the insight to interpret the host structures that together with related seismic and geoscience data, suggest causative mechanisms of the New Madrid seismic zone and other seismogenic regions of the eastern United States. As a result, we conclude that interpretations of geopotential anomalies are an essential ingredient in seismotectonic studies in the eastern United States, but they are only one of several tools required in the concerted effort of assessing seismic hazards. The presence of anomalies with a particular set of attributes neither confirms nor denies the possible spatial relationship to seismicity.

The Western Limit of Iapetan Rifting in the Eastern United States: A New Assessment

2020 ◽  
Vol 91 (6) ◽  
pp. 3483-3495
Author(s):  
Christine A. Powell ◽  
William A. Thomas ◽  
Robert D. Hatcher
Keyword(s):  
United States ◽  
Seismic Hazard ◽  
Atlantic Coastal Plain ◽  
Hazard Evaluation ◽  
Earthquake Activity ◽  
Blue Ridge ◽  
Mantle Structure ◽  
Eastern United States ◽  
Appalachian Plateau ◽  
Lithospheric Thickness

Abstract Specifying the extent and location of rifted, crystalline Precambrian crust in the eastern United States is important for seismic hazard evaluation and for models that relate upper-mantle structure to ancient tectonic features and ongoing tectonism. As currently depicted in the National Seismic Hazard Maps (NSHM), the western limit of Iapetan rifted crust is beneath the Appalachian plateau physiographic province, west of the Valley and Ridge province. New estimates of crustal thickness using EarthScope Transportable Array and other data do not support the presence of rifted crust beneath the Blue Ridge, Valley and Ridge, and Appalachian plateau physiographic provinces. Crustal thicknesses exceed 45 km throughout most of this region. The crust thins to the southeast beneath the southeastern part of the Piedmont physiographic province and is only 36 km thick near the edge of the Atlantic coastal plain. We suggest that the western limit of Iapetan rift-extended crust is east of the Blue Ridge province and is associated with the prominent Appalachian gravity gradient. This location coincides with palinspastic reconstructions based on geologic data for the Iapetan rifted margin. Recognition of thick crust beneath the Blue Ridge and Valley and Ridge provinces, unextended by Iapetan rifting, will support more robust modeling of the effects of mantle structure (such as delamination and abrupt changes in lithospheric thickness) on ongoing tectonism and earthquake activity in the eastern United States and will provide more accurate seismotectonic zonation in the NSHM.

Temporal and Spatial Clustering of Earthquake Activity in the Central and Eastern United States

1988 ◽  
Vol 59 (4) ◽  
pp. 299-304 ◽  
Author(s):  
Kevin J. Coppersmith
Keyword(s):  
United States ◽  
Spatial Clustering ◽  
Historical Seismicity ◽  
Earthquake Activity ◽  
Eastern United States ◽  
Recurrence Rates ◽  
Earthquake Sources ◽  
Recurrence Intervals ◽  
The Subject ◽  
Earthquake Potential

Abstract Seismic hazard assessments in the central and eastern United States (CEUS) usually rely heavily on the historical seismicity record to define the location of earthquake sources as well as the recurrence rate of these sources. Therefore, the stationarity of earthquake activity in time and space is very important to assessing the likelihood of future earthquakes at various locations. Earthquake recurrence intervals, which are on the order of hundreds to thousands of years, have been developed from paleoseismic data at New Madrid, Charleston, Charlevoix, and the Meers fault. The recurrence rates imply cumulative Quaternary displacements that are much larger than have been observed. One explanation for this discrepancy is temporal clustering of earthquake activity whereby active clusters are separated by long periods of quiescence. Available data suggest that active clusters consist of two or more earthquakes and last for longer than several hundred to a few thousand years. The spatial extent of active dusters in the CEUS is the subject of ongoing studies and preliminary data suggest that the active zone is generally in the region of the large observed earthquakes and on-going smaller magnitude seismicity. However, the historical seismic quiescence of the Meers fault, despite geologic evidence for recent activity, points to the need for geologic studies to supplement seismicity data in identifying seismic sources and evaluating their earthquake potential.

A ground-motion prediction model for small-to-moderate induced earthquakes for Central and Eastern United States

2021 ◽  
pp. 875529302110160
Author(s):  
Zoya Farajpour ◽  
Shahram Pezeshk
Keyword(s):  
United States ◽  
Ground Motion ◽  
Gulf Coast ◽  
Hazard Evaluation ◽  
Eastern United States ◽  
Induced Earthquakes ◽  
Ground Acceleration ◽  
Mixed Effect ◽  
Ground Motion Model ◽  
Tectonic Earthquakes

This study presents a new ground motion model (GMM) for small-to-moderate potentially induced earthquakes for Central and Eastern United States (CEUS). We used a hybrid empirical model as the base model, which was developed and calibrated for tectonic events in Central and Eastern North America (CENA) as part of the Next-generation Attenuation-East (NGA-East) project. We calibrated the base model using a comprehensive database of potentially induced ground motions with smaller magnitudes and shallower depths than tectonic earthquakes, excluding all earthquake events and stations within the Gulf Coast region. We determined the model functional form coefficients using a mixed-effect regression procedure. The proposed GMM is derived for the peak ground acceleration and response-spectral ordinates at periods ranging from 0.01 to 10.0s, moment magnitudes ranging from 3.0 to 5.8, and hypocentral distances up to 200km. The performance of the proposed GMM is evaluated through a set of comprehensive residual analyses. Furthermore, we compared the proposed GMM with recently published GMMs with the observed data for CEUS. The proposed GMM could apply in long-term and short-term US Geological Survey National Seismic Hazard Maps and for the hazard evaluation of induced seismicity.

Scientific overview and historical context of the 1811-1812 New Madrid earthquake sequence

2009 ◽  
Vol 47 (2-3) ◽  
Author(s):  
S. E. Hough
Keyword(s):  
United States ◽  
Seismic Waves ◽  
Ground Motions ◽  
The United States ◽  
Seismic Zone ◽  
Eastern United States ◽  
Triggered Earthquakes ◽  
Macroseismic Effects ◽  
Earthquake Research ◽  
New Madrid

The central and eastern United States has experienced only 5 historic earthquakes with Mw 7.0, four during the New Madrid sequence of 1811-1812: three principal mainshocks and the so-called «dawn aftershock» following the first mainshock. Much of the historic earthquake research done in the United States has focused on the New Madrid Seismic Zone (NMSZ), because the largest New Madrid earthquakes may represent the archetype for the most damaging earthquakes to be expected in intraplate regions. Published magnitude values ranging from 7.0 to 8.75 have generally been based on macroseismic effects, which provide the most direct constraint on source size for the events. Critical to the interpretation of these accounts is an understanding of their historic context. Early settlments clustered along waterways, where substantial amplification of seismic waves is expected. Analyzing the New Madrid intensity values with a consideration of these effects yields preferred values of Mw 7.2-7.3, 7.0, and 7.4-7.5 for the December, January, and February mainshocks, respectively, and of 7.0 for the «dawn aftershock». These values are consistent with other lines of evidence, including scaling relationships. Finally, I show that accounts from the New Madrid sequence reveal evidence for remotely triggered earthquakes well outside the NMSZ. Remotely triggered earthquakes represent a potentially important new wrinkle in historic earthquake research, as their ground motions can sometimes be confused with mainshock ground motions.

Mother or Wife?

2012 ◽  
Vol 43 (4) ◽  
pp. 232-242 ◽  
Author(s):  
Phia S. Salter ◽  
Glenn Adams
Keyword(s):  
United States ◽  
Resource Allocation ◽  
Cultural Psychology ◽  
The United States ◽  
Personal Relationship ◽  
Three Dimensions ◽  
Church Membership ◽  
Cultural Dynamics ◽  
Psychology Perspective ◽  
Cultural Ecological

Inspired by “Mother or Wife” African dilemma tales, the present research utilizes a cultural psychology perspective to explore the dynamic, mutual constitution of personal relationship tendencies and cultural-ecological affordances for neoliberal subjectivity and abstracted independence. We administered a resource allocation task in Ghana and the United States to assess the prioritization of conjugal/nuclear relationships over consanguine/kin relationships along three dimensions of sociocultural variation: nation (American and Ghanaian), residence (urban and rural), and church membership (Pentecostal Charismatic and Traditional Western Mission). Results show that tendencies to prioritize nuclear over kin relationships – especially spouses over parents – were greater among participants in the first compared to the second of each pair. Discussion considers issues for a cultural psychology of cultural dynamics.

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