scholarly journals Stress field characterisation in Nickel Rim South Mine using seismic stress inversion

2017 ◽  
Author(s):  
Yousef Abolfazlzadeh ◽  
Stephen McKinnon
Keyword(s):  
Stress Field ◽  
Stress Inversion ◽  
Seismic Stress

Direct stress field estimation through waveform matching

2020 ◽  
Vol 221 (2) ◽  
pp. 843-856
Author(s):  
Wenhuan Kuang ◽  
Jie Zhang
Keyword(s):  
Stress Field ◽  
Focal Mechanism ◽  
Stress Pattern ◽  
P Wave ◽  
Local Source ◽  
Stress Inversion ◽  
Inversion Process ◽  
Physical Relationship ◽  
New Approach ◽  
Field Estimation

SUMMARY Conventionally, the routine workflow of stress field estimation from seismic data consists of two steps: focal mechanism inversion and stress inversion. This two-step workflow suffers from the cumulative uncertainties of both the focal mechanism inversion process and the stress inversion process. To mitigate the cumulative errors, a few previous studies have put efforts to directly estimate the stress field using P-wave polarities. In this study, we develop a new approach to directly estimate tectonic stress fields with better accuracy through waveform matching. This new approach combines the two steps into a one-step workflow to mitigate the cumulative uncertainties through the physical relationship between a stress field and the recorded waveforms. This method assumes a homogeneous stress field in space in the local source region and that the fault slip occurs in the direction of the resolved shear stress acting on the fault plane. Under these assumptions, the stress pattern that generates the theoretical waveforms that best fit the waveforms observed is directly retrieved as the true stress field. The merits of the new approach include that this approach can mitigate the cumulative uncertainties suffered from the conventional two-step workflow and does not require determination of the focal mechanisms of each event; thus, this method is applicable to data sets with few stations. Synthetic tests with and without noise are conducted to demonstrate the performance and merits of this method. Then, the new approach is applied to a real data set from central Oklahoma between March 2013 and March 2016. The resulting stress pattern is consistent with that estimated from previous studies examining the same region. These applications show the benefits and validity of the new approach.

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>

Physical modeling of fluid-filled fractures using the dynamic photoelasticity technique

Geophysics ◽  
2021 ◽  
Vol 86 (1) ◽  
pp. T33-T43
Author(s):  
Haitao Cao ◽  
Ezequiel Medici ◽  
Roohollah Askari
Keyword(s):  
Wave Propagation ◽  
Stress Field ◽  
Seismic Wave ◽  
Seismic Data ◽  
Physical Modeling ◽  
Complex Geometry ◽  
Seismic Wave Propagation ◽  
Fluid Viscosity ◽  
Dynamic Photoelasticity ◽  
Seismic Stress

We have developed an optical apparatus based on the dynamic photoelasticity technique to visualize and analyze the propagation of the Krauklis wave within an analog fluid-filled fracture. Although dynamic photoelasticity has been used by others to study seismic wave propagation, this study adds a quantitative analysis addressing dispersion properties. We physically modeled a fluid-filled fracture using transparent photoelastic-sensitive polycarbonate and nonsensitive acrylic plates. Then we used a pixel-based framework to analyze the dispersion of a Krauklis wave excited in the fracture. Through this pixel-based framework, we thus demonstrate that the dynamic photoelasticity technique can quantitatively describe seismic wave propagation with a quality similar to experiments using conventional transducers (receivers) while additionally visualizing the seismic stress field. We observe that an increase in the fluid viscosity results in a decrease in the velocity of the Krauklis wave. We also determine the capability of the method to analyze seismic data in the case of complex geometry by modeling a sawtooth fracture. The fracture’s geometry can strongly affect the characteristics of the Krauklis wave as we note a higher Krauklis wave velocity for the sawtooth case, as well as greater perturbation of the stress field.

scholarly journals Evidence for Basement Reactivation during the Opening of the Labrador Sea from the Makkovik Province, Labrador, Canada: Insights from Field Data and Numerical Models

Geosciences ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 308 ◽  
Author(s):  
Alexander Peace ◽  
Edward Dempsey ◽  
Christian Schiffer ◽  
J. Welford ◽  
Ken McCaffrey ◽  
...  
Keyword(s):  
Stress Field ◽  
Numerical Models ◽  
Passive Margin ◽  
Labrador Sea ◽  
Spreading Ridge ◽  
Stress Inversion ◽  
Eastern Canada ◽  
Stress Regime ◽  
General Direction ◽  
Continental Breakup

The onshore exposures adjacent to modern, offshore passive continental margins may preserve evidence of deformation from the pre-, syn-, and post-rift phases of continental breakup that allow us to investigate the processes associated with and controlling rifting and breakup. Here, we characterize onshore brittle deformation and pre-rift basement metamorphic mineral fabric from onshore Labrador in Eastern Canada in the Palaeoproterozoic Aillik Domain of the Makkovik Province. Stress inversion (1) was applied to these data and then compared to (2) numerical models of hybrid slip and dilation tendency, (3) independent calculations of the regional geopotential stress field, and (4) analyses of palaeo-stress in proximal regions from previous work. The stress inversion shows well-constrained extensional deformation perpendicular to the passive margin, likely related to pre-breakup rifting in the proto-Labrador Sea. Hybrid slip and dilatation analysis indicates that inherited basement structures were likely oriented in a favorable orientation to be reactivated during rifting. Reconstructed geopotential stresses illuminate changes of the ambient stress field over time and confirm the present paleo-stress estimates. The new results and numerical models provide a consistent picture of the late Mesozoic-Cenozoic lithospheric stress field evolution in the Labrador Sea region. The proto-Labrador Sea region was characterized by a persistent E–W (coast-perpendicular) extensional stress regime, which we interpret as the pre-breakup continental rifting that finally led to continental breakup. Later, the ridge push of the Labrador Sea spreading ridge maintained this general direction of extension. We see indications for anti-clockwise rotation of the direction of extension along some of the passive margins. However, extreme persistent N–S-oriented extension as indicated by studies further north in West Greenland cannot be confirmed.

scholarly journals Mapping the pre and post seismic crustal stress heterogeneity analogous to 2016, Mw 7.8, Kaikoura quake, New Zealand

2021 ◽  
Author(s):  
Anupama M. ◽  
Sunil P.S.
Keyword(s):  
New Zealand ◽  
Stress Field ◽  
B Value ◽  
Rupture Zone ◽  
Fault System ◽  
Primary Role ◽  
Epicentral Area ◽  
B Values ◽  
The North ◽  
Seismic Stress

Abstract Heterogeneity of pre and post seismic stress states associated to any earthquake play a primary role in understanding the earthquake mechanism and hazard assessment of a seismically dynamic region. The Mw 7.8, November 14, 2016 Kaikoura, New Zealand earthquake offer an unprecedented possibility to observe the heterogeneity in stress field over a very complex fault system wherein subduction zone converges with the strike slip faults system. Here we report the pre and post seismic stress field asperity first time in terms of spatial and temporal variations of b-values associated to the Kaikoura main-shock. Pre seismic spatial disparity of b-value indicates the existence of two prominent low b-value clusters, one towards southwest closer to the epicenter and other to the north of the rupture zone. During co seismic period, owing to the stress release near the epicentral area, the pattern of prominent low b-value pattern has become negligible in the post seismic period. However, the pattern of low b-value in the north of the rupture zone remains similar in the post seismic period indicates the unreleased strain energy in the province. The temporal evaluation of the earthquakes frequency magnitude distributions over a period of two decades also showed an analogous pattern that the b-values were decreased considerably before the large earthquakes in the expanse, which could spawn a larger future earthquakes in the vicinity.

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