Fault Plane Solutions and the State of Stress in New England

1980 ◽  
Vol 51 (2) ◽  
pp. 3-12
Author(s):  
Timothy Graham ◽  
Edward F. Chiburis
Keyword(s):  
Stress Field ◽  
New England ◽  
Fault Plane ◽  
The State ◽  
Fault Plane Solutions ◽  
Compressional Stress ◽  
Southern New England ◽  
State Of Stress ◽  
Reverse Faulting ◽  
East West

Abstract An analysis of eighteen New England fault plane solutions indicates that the area can be largely characterized by reverse faulting on north to northeasterly striking fault planes. This implies that New England is predominantly influenced by an east-west to southeast-northwest compressional stress field. This generalization may not apply in certain areas of southern New England.

scholarly journals A holistic seismotectonic model of Delhi region

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Brijesh K. Bansal ◽  
Kapil Mohan ◽  
Mithila Verma ◽  
Anup K. Sutar
Keyword(s):  
Strain Energy ◽  
Fault Plane ◽  
Near Field ◽  
Energy Estimates ◽  
The West ◽  
Fault Plane Solutions ◽  
Northern India ◽  
Structural Environment ◽  
Reverse Faulting ◽  
Using Data

AbstractDelhi region in northern India experiences frequent shaking due to both far-field and near-field earthquakes from the Himalayan and local sources, respectively. The recent M3.5 and M3.4 earthquakes of 12th April 2020 and 10th May 2020 respectively in northeast Delhi and M4.4 earthquake of 29th May 2020 near Rohtak (~ 50 km west of Delhi), followed by more than a dozen aftershocks, created panic in this densely populated habitat. The past seismic history and the current activity emphasize the need to revisit the subsurface structural setting and its association with the seismicity of the region. Fault plane solutions are determined using data collected from a dense network in Delhi region. The strain energy released in the last two decades is also estimated to understand the subsurface structural environment. Based on fault plane solutions, together with information obtained from strain energy estimates and the available geophysical and geological studies, it is inferred that the Delhi region is sitting on two contrasting structural environments: reverse faulting in the west and normal faulting in the east, separated by the NE-SW trending Delhi Hardwar Ridge/Mahendragarh-Dehradun Fault (DHR-MDF). The WNW-ESE trending Delhi Sargoda Ridge (DSR), which intersects DHR-MDF in the west, is inferred as a thrust fault. The transfer of stress from the interaction zone of DHR-MDF and DSR to nearby smaller faults could further contribute to the scattered shallow seismicity in Delhi region.

Analysis of Shallow Microearthquakes in the South Sebec Seismic Zone, Maine, 1989–1990

1992 ◽  
Vol 63 (4) ◽  
pp. 557-566 ◽  
Author(s):  
William E. Doll ◽  
Carol D. Rea ◽  
John E. Ebel ◽  
Sandra J. Craven ◽  
John J. Cipar
Keyword(s):  
New England ◽  
Satellite Images ◽  
Fault Plane ◽  
Seismic Zone ◽  
Fault Plane Solutions ◽  
Motion Data ◽  
First Motion ◽  
High Level ◽  
Surface Geology

Abstract Fifteen years of regional monitoring by the New England Seismic Network indicated a locally high level of seismicity near South Sebec, between the towns of Milo and Dover-Foxcroft in central Maine. Most of the events were located in a diffuse zone south of the distinctive, ENE trending Harriman Pond Fault (HPF) which is indicated by brittle deformation in outcrop and is represented as a depression in topographic maps and satellite images. A portable network consisting of both digital and analog instruments was deployed during the summers of 1989 and 1990 in order to characterize the pattern of the microearthquakes and to determine high-resolution epicenters, depths, and fault plane solutions. Seventy-three events were detected during the experiment, of which 28 could be located. Many of the events south of the fault lie along a NNW trending line which has no major expression in the surface geology. Only, a few of the events are subparallel to the HPF. The first motion data were insufficient for the determination of any fault plane solutions.

Quaternary normal and reverse faulting and the state of stress in the central Andes of south Peru

Tectonics ◽  
1985 ◽  
Vol 4 (7) ◽  
pp. 739-780 ◽  
Author(s):  
Michel Sébrier ◽  
Jacques Louis Mercier ◽  
François Mégard ◽  
Gérard Laubacher ◽  
Evelyne Carey-Gailhardis
Keyword(s):  
Central Andes ◽  
The State ◽  
State Of Stress ◽  
Reverse Faulting

Tectonic stress patterns along the Vrancea subcrustal zone from the inversion of focal mechanisms data

2021 ◽  
Author(s):  
Andreea Craiu ◽  
Marius Craiu ◽  
Mariu Mihai ◽  
Elena Manea ◽  
Alexandru Marmureanu
Keyword(s):  
Stress Field ◽  
Large Scale ◽  
Fault Plane ◽  
Numerical Models ◽  
Moment Tensor ◽  
Stress Inversion ◽  
Slab Geometry ◽  
Fault Plane Solutions ◽  
Current Stress ◽  
Stress Patterns

<p>The Vrancea zone is an unique area with both crustal and intermediate-depth seismic activity and constitutes one of the most active seismic area in Europe.  An intense and persistent seismicity is generated between 60 and 180 km depth, within a relic slab sinking nearly vertical in the Earth’s mantle due to the increasing of the stress state within this volume. At intermediate-depths, large magnitude events are frequent, i.e. four earthquakes with moment magnitudes (Mw) >7 occurred in the last century. An unique slab geometry, likely preserved until the present, causes stress localization due to the slab bending and subsequent stress release resulting in large mantle earthquakes in the region.</p><p>In this study, we evaluate the current stress field along the Vrancea subcrustal region by computing the fault plane solutions of 422 seismic events since January 2005. The continuous development of the National Seismic Network allows us to constrain the fault plane solutions and subsequently to evaluate the current stress field.</p><p>The main style of faulting for Vrancea subcrustal events presents a predominant reverse one, with two main earthquakes categories: the first one with the nodal planes oriented NE-SW parallel with the Carpathian Arc and the second one with the nodal planes oriented NW-SE perpendicular on the Carpathian Arc. The main axis of the moment tensor may indicate a predominant compressional stress field (Tpl>45<sup>0</sup> Ppl<45<sup>0</sup>). Another characteristic of  the Vrancea subcrustal zone is the tendency of the extension axis T to be almost vertical and the compression axis P being almost horizontal.</p><p>The results of stress inversion indicate a dominant reverse faulting style, with an average stress regime index of 2.9. Other tectonic regimes were observed in the present dataset as normal and strike-slip but they are retrieved for a restrained number of events.</p><p>The stress patterns obtained from formal stress inversion of focal mechanism solutions reveal many features of the current stress field that were not captured by large-scale numerical models.</p>

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