Determining contemporary stress directions from neotectonic joint systems

1991 ◽  
Vol 337 (1645) ◽  
pp. 29-40 ◽  
Keyword(s):  
Stress Field ◽  
Fault Plane ◽  
Horizontal Stress ◽  
Tectonic Stress ◽  
Stress Fields ◽  
Ebro Basin ◽  
Fault Plane Solutions ◽  
Near Surface ◽  
Initiation And Propagation

A neotectonic joint is a crack which propagated in a tectonic stress field that has persisted with little or no change of orientation until the present day. Investigating neotectonic joints is of value because the approximate orientation of the contemporary stress field can be inferred from them. Although exposed neotectonic joints in the flat-lying sedimentary rocks of some cratons are related to regional stress fields, their initiation and propagation occurred close to the Earth’s surface. For example, neotectonic joints in the centre of the Ebro basin (N. Spain) preferentially developed in a thin, near-surface channel sited within a sequence of weak Miocene limestones underlying the upper levels of plateaux. The Ebro basin joints strike uniformly NNW-SSE throughout an area of at least 10 000 km 2 and they are parallel or subparallel to the direction of greatest horizontal stress extrapolated from in situ stress measurements and fault-plane solutions of earthquakes.

The tectonic stress and tectonic motion direction in the Pacific and Adjacent areas as calculated from earthquake fault plane solutions

1965 ◽  
Vol 55 (1) ◽  
pp. 147-152 ◽  
Author(s):  
A. E. Scheidegger
Keyword(s):  
Fault Plane ◽  
Horizontal Stress ◽  
Tectonic Stress ◽  
Pacific Basin ◽  
Motion Direction ◽  
Fault Plane Solutions ◽  
Earthquake Fault ◽  
The Pacific ◽  
Tectonic Motion ◽  
Consistent Picture

Abstract The best P and T axes as well as the best normals to the null directions were calculated for groups of earthquake fault plane solutions belonging to 29 areas of the Pacific Basin and vicinity. The method employed was one developed in an earlier paper of the writer; it is based on a calculation of the eigenvectors of a quadratic form. It is shown that the principal horizontal stress (PHS) directions obtained in this fashion are in excellent agreement with those obtained from other evidence. In the Western Pacific Basin and vicinity the calculations were sufficiently dense to determine PHS trajectories; the latter are shown and yield a consistent picture of the area in question.

THEORETICAL ESTIMATION OF IN-SITU STRESSED STATE OF ROCK MASSIFES UNDER CONDITIONS OF

2019 ◽  
Vol 4 (1) ◽  
pp. 292-304
Author(s):  
I.L. Pankov ◽  
Keyword(s):  
Stress Distribution ◽  
Stress Field ◽  
Stressed State ◽  
Deformation Modulus ◽  
Horizontal Stress ◽  
Tectonic Stress ◽  
Theoretical Estimation ◽  
Vertical Pressure ◽  
The Relationship

System of physical equations was obtained, which determines the relationship between main stresses and corresponding strains for the conditions of the all-round compression tectonic stress field in a virgin compacted intact massif of rocks. Estimated formulas for determining the maximum and minimum horizontal stresses of an intact massif, which is under conditions of plane-directional tectonic influence depending on the factors of vertical pressure, porosity and deformation modulus of rocks, are obtained. The behavior of the horizontal stress distribution from the vertical pressure is considered under the influence of various factors.

The tectonic stress and tectonic motion direction in Europe and Western Asia as calculated from earthquake fault plane solutions

1964 ◽  
Vol 54 (5A) ◽  
pp. 1519-1528 ◽  
Author(s):  
A. E. Scheidegger
Keyword(s):  
Fault Plane ◽  
Horizontal Stress ◽  
Tectonic Stress ◽  
Motion Direction ◽  
Fault Plane Solutions ◽  
Plane Normal ◽  
Western Asia ◽  
Best Fitting ◽  
Tectonic Motion ◽  
Vector Sum

Abstract The statistics of fault plane solutions of earthquakes is further analyzed and it is shown that, to find a best axis or best plane to a set of axes, the eigenvectors of a certain matrix must be calculated. The justification for this procedure follows from the same argument as that of Fisher who showed that the best of a series of directions is obtained by forming the vector sum. The eigenvector technique is then applied to the pertinent axes of fault plane solutions of earthquakes that occurred in Europe and Western Asia. It is shown that, in this region, the focal mechanisms of the earthquakes tend to orient themselves in such a fashion that the P axes coincide with the principal horizontal stress directions, the latter being normal to the geographically prominent features. The null axes tend to lie in a plane normal to the best fitting P axes. The chief random element enters into the orientation of the T axes. All this is in conformity with the predictions of theory.

Fractures in the northern plains, stream patterns, and the midcontinent stress field

1987 ◽  
Vol 24 (6) ◽  
pp. 1086-1097 ◽  
Author(s):  
Mel R. Stauffer ◽  
Don J. Gendzwill
Keyword(s):  
Stress Field ◽  
Horizontal Stress ◽  
The Body ◽  
North American Plate ◽  
Plate Motion ◽  
Viscous Drag ◽  
Near Surface ◽  
The North ◽  
Elastic Rebound ◽  
Western North Dakota

Fractures in Late Cretaceous to Late Pleistocene sediments in Saskatchewan, eastern Montana, and western North Dakota form two vertical, orthogonal sets trending northeast–southwest and northwest–southeast. The pattern is consistent, regardless of rock type or age (except for concretionary sandstone). Both sets appear to be extensional in origin and are similar in character to joints in Alberta. Modem stream valleys also trend in the same two dominant directions and may be controlled by the underlying fractures.Elevation variations on the sub-Mannville (Early Cretaceous) unconformity form a rectilinear pattern also parallel to the fracture sets, suggesting that fracturing was initiated at least as early as Late Jurassic. It may have begun earlier, but there are insufficient data at present to extend the time of initiation.We interpret the fractures as the result of vertical uplift together with plate motion: the westward drift of North America. The northeast–southwest-directed maximum principal horizontal stress of the midcontinent stress field is generated by viscous drag effects between the North American plate and the mantle. Vertical uplift, erosion, or both together produce a horizontal tensile state in near-surface materials, and with the addition of a directed horizontal stress through plate motion, vertical tension cracks are generated parallel to that horizontal stress (northeast–southwest). Nearly instantaneous elastic rebound results in the production of second-order joints (northwest–southeast) perpendicular to the first. In this manner, the body of rock is being subjected with time to complex alternation of northeast–southwest and northwest–southeast horizontal stresses, resulting in the continuous and contemporaneous production of two perpendicular extensional joint sets.

Aftershocks of the Benham nuclear explosion

1969 ◽  
Vol 59 (6) ◽  
pp. 2271-2281
Author(s):  
R. M. Hamilton ◽  
J. H. Healy
Keyword(s):  
Fault Plane ◽  
Nuclear Explosion ◽  
Test Site ◽  
Strike Slip ◽  
Nevada Test Site ◽  
Ground Zero ◽  
Fault Plane Solutions ◽  
Fault Movement ◽  
Near Surface ◽  
Earthquake Distribution

abstract The Benham nuclear explosion, a 1.1 megaton test 1.4 km beneath Pahute Mesa at the Nevada Test Site, initiated a sequence of earthquakes lasting several months. The epicenters of these shocks were located within 13 km of ground zero in several linear zones that parallel the regional fault trends. Focal depths range from near surface to 6 km. The earthquakes are not located in the zone of the major ground breakage. The earthquake distribution and fault plane solutions together indicate that both right-lateral strike-slip fault movement and dip-slip fault movement occurred. The explosion apparently caused the release of natural tectonic strain.

scholarly journals A semi-quantitative method to combine tectonic stress indicators: example from the Southern Calabrian Arc (Italy)

2020 ◽  
Vol 56 (1) ◽  
pp. 280
Author(s):  
Salvatore Scudero ◽  
Giorgio De Guidi ◽  
Riccardo Caputo ◽  
Vincenzo Perdicaro
Keyword(s):  
Stress Field ◽  
Original Data ◽  
Horizontal Stress ◽  
Tectonic Stress ◽  
Structural Features ◽  
Interesting Case ◽  
Stress Indicators ◽  
Spatial And Temporal Scales ◽  
Independent Information ◽  
Minimum Horizontal Stress

Databases of tectonic stress indicators are commonly based on different types of observations at different spatial and temporal scales. Each single indicator can be variously representative of the real stress field and the relative importance of all the indicators should be accounted for before any following elaboration. We propose a semi-quantitative procedure which assigns weights to each indicator on the basis of its quality and its representative volume. In this way the indicators can be reliably combined to produce, for example, stress field maps or stress trajectories. The proposed weighting criterion has been applied to a dataset of 440 crustal stress indicators specifically compiled, gathering focal mechanisms and geological data from the literature, and original data from structural features derived from devoted fieldwork, for the southern part of the Calabrian Arc (Italy). This area represents an interesting case study because of its complex geodynamic and structural arrangement. Data were ranked and the orientation of the minimum horizontal stress (Sh) has been interpolated and smoothed on a regular grid. We drew maps of the principal stress axes and inferred the stress regimes over the investigated area. Results are in agreement with independent information from the literature and display the non-uniform orientation of the tectonic stresses and the occurrence of perturbations both at regional and local scale.

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