State of stress in the conterminous United States

Abstract

Inferring principal stress directions from geologic data, focal mechanisms, and in situ stress measurements, we have prepared a map of principal horizontal stress orientations for the conterminous United States. Stress provinces with linear dimensions which range between 100 and 2000 km were defined on the basis of the directions and relative magnitude of principal stresses. Within a given province, stress orientations appear quite uniform (usually within the estimated range of accuracy of the different methods used to determine stress). Available data on the transition in stress direction between the different stress provinces indicate that these transitions can be abrupt, occurring over <75 km in places. In the western United States, a region of active tectonism characterized by high levels of seismicity and generally high heat flow, the stress pattern is complex, but numerous stress provinces can be well delineated.

Stress direction history of the western United States and Mexico since 85 Ma

“…[9] Zoback and Zoback [1980] interpreted the contemporary data from this region as indicating a number of stress direction ''provinces'' separated by narrow transitions. Two regions of notably differentŝ 1H (WNW-ESE) were recognized in the northern Rocky Mountains and in the Colorado Plateau.…”

Effects of crustal stresses on fluid transport in fractured rock: case studies from northeastern and southwestern USA

“…For convenience and ease of referencing, the maximum horizontal stress, S H ′/K i d m , and the minimum horizontal stress, S h ′/K i d m , are oriented E-W and N-S, respectively. These stress orientations differ somewhat from those determined by Seeber et al (1998), but are generally consistent with principal stress directions for the northeastern United States (Zoback and Zoback 1989). The values of 2.25, 1.00, and 1.15 are the stress ratios determined by Seeber et al (1998) from shallow (<5 km) earthquake focal mechanisms.…”

“…Earthquake studies indicate that this tectonic environment has continued to evolve (Doser et al 1992), with Alpine situated in a transitional zone between competing extensional provinces associated with the southern Rio Grande rift and the southern Great Plains (Zoback and Zoback 1989). Focal mechanism analyses derived from the mainshock and two of the larger aftershocks of the 1995 Alpine earthquake (Doser 1998) describe normal Fig.…”

“…Other nearby regional structures include broad, low amplitude folds (Lyttle and Epstein 1987) with mostly gentle topographic relief. Zoback and Zoback (1989) summarize contemporary principal stress orientations for the eastern United States, including the Newark Basin, and present the orientation of the greatest horizontal principal stress, S H , as NE-SW to E-W. Seeber et al (1998) argue that the least horizontal principal stress, S h , and the vertical principal stress, S v , have similar magnitudes in the Newark Basin and would be expected to change relative positions, thereby resulting in both thrust (S H >S h >S v ) and strike-slip (S H >S v >S h ) faulting. These investigators also apply source data from a number of recent earthquakes in the Newark Basin to a fault kinematic model proposed by Michael (1984) to establish the direction of S H and the principal stress ratios for the region.…”

Seismicity and recent stress regime of Diyala City, Iraq–Iran border

“…A quality ranking scheme of stress orientations determined from focal mechanisms was developed by Zoback and Zoback (1989Zoback ( , 1991 and Zoback (1992) and updated by Sperner et al (2003). Five qualities are used in ranking the data, which are between A and E, with A being the highest quality and E the lowest.…”