scholarly journals Time-Dependent Stresses From Fluid Extraction and Diffusion With Applications to Induced Seismicity

2020 ◽  
Vol 87 (8) ◽  
Author(s):  
Valère Lambert ◽  
Victor C. Tsai
Keyword(s):  
Principal Stress ◽  
Induced Seismicity ◽  
Focal Mechanisms ◽  
Time Dependent ◽  
Spatial Gradient ◽  
Fluid Extraction ◽  
Earthquake Focal Mechanisms ◽  
Stress Changes ◽  
Stress Directions ◽  
And Diffusion

Abstract Over recent decades, it has become clear that the extraction of fluids from underground reservoirs can be linked to seismicity and aseismic deformation around producing fields. Using a simple model with uniform fluid extraction from a reservoir, Segall (1989, “Earthquakes Triggered by Fluid Extraction,” Geology, 17(10), pp. 942–946) illustrated how poroelastic stresses resulting from fluid withdrawal may be consistent with earthquake focal mechanisms surrounding some producing fields. Since these stress fields depend on the spatial gradient of the change in pore fluid content within the reservoir, both quantitative and qualitative predictions of the stress changes surrounding a reservoir may be considerably affected by assumptions in the geometry and hydraulic properties of the producing zone. Here, we expand upon the work of Segall (1989, “Earthquakes Triggered by Fluid Extraction,” Geology, 17, pp. 942–946 and 1985, “Stress and Subsidence Resulting From Subsurface Fluid Withdrawal in the Epicentral Region of the 1983 Coalinga Earthquake,” J. Geophys. Res. Solid Earth, 90, pp. 6801–6816) to provide a quantitative analysis of the surrounding stresses resulting from fluid extraction and diffusion in a horizontal reservoir. In particular, when considering the diffusion of fluids, the spatial pattern and magnitude of imposed stresses is controlled by the ratio between the volumetric rate of fluid extraction and the reservoir diffusivity. Moreover, the effective reservoir length expands over time along with the diffusion front, predicting a time-dependent rotation of the induced principal stresses from relative tension to compression along the ends of the producing zone. This reversal in perturbed principal stress directions may manifest as a rotation in earthquake focal mechanisms or varied sensitivity to poroelastic triggering, depending upon the criticality of the pre-existing stress state and fault orientations, which may explain inferred rotations in principal stress directions associated with some induced seismicity.

A review of methods for determining stress fields from earthquakes focal mechanisms; Application to the Sierentz 1980 seismic crisis (Upper Rhine graben)

2013 ◽  
Vol 184 (4-5) ◽  
pp. 319-334 ◽  
Author(s):  
Julie Maury ◽  
François H. Cornet ◽  
Louis Dorbath
Keyword(s):  
Stress Field ◽  
Principal Stress ◽  
Confidence Level ◽  
Focal Mechanisms ◽  
Upper Rhine Graben ◽  
Earthquake Focal Mechanisms ◽  
Rhine Graben ◽  
Minimum Principal Stress ◽  
Stress Directions ◽  
Upper Rhine

Abstract The inversion of earthquake focal mechanisms is one of the few tools available for determining principal stress directions at seismogenic depths. Various methods have been proposed for performing such inversions. For three of the most commonly used methods, including one that has been proposed by Jacques Angelier, we discuss the physical assumptions and the error determination and then we propose an extension for one of the methods. All four methods are then applied for evaluating the stress field in the Upper Rhine graben. They are applied to seismic data recorded with a temporary monitoring network that was deployed 12 hours after the magnitude Mw = 4.4 Sierentz earthquake, which occurred on July 15, 1980. While differences in principal stress directions can be as much as 28° depending on the method used for the principal stress direction determination (orientation of the minimum principal stress has been found to range from N051°E with a 27° plunge to N090° E with a 20° plunge), the 90% confidence level associated with each method varies from 11° to 27°. Moreover, these various methods yield fairly diverse values for the R factor that characterizes relative differences between principal stress magnitudes (from R = 0.7 with a 0.2 90% confidence level to R = 0.3 with a 0.2 90% confidence level). Furthermore all three methods leave some focal mechanisms unexplained. These are then declared to be the result of heterogeneity and are not considered for the inversion. It is concluded that earthquake focal mechanisms inversions lack resolution for stress field evaluation at depth if no proper attention is given to the event independence hypothesis. When proper attention is given to this hypothesis, a resolution of the order of 15° may be achieved. The minimum principal stress orientation derived with these various focal mechanisms inversions differs by 4 to 36° from the orientation determined from borehole breakouts observed in Basel, in a 5 km deep well (N054°E ± 14°), located some 20 km from Sierentz. The solution that fits best borehole breakout observations is that which satisfies the minimum number (three) of prerequisite physical assumptions.

scholarly journals Full-waveform event location and moment tensor inversion for induced seismicity

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. KS39-KS57 ◽  
Author(s):  
Chris Willacy ◽  
Ewoud van Dedem ◽  
Sara Minisini ◽  
Junlun Li ◽  
Jan-Willem Blokland ◽  
...  
Keyword(s):  
Induced Seismicity ◽  
Moment Tensor ◽  
Focal Mechanisms ◽  
Moment Tensor Inversion ◽  
Earthquake Activity ◽  
Lower Velocity ◽  
Full Waveform ◽  
Stress Changes ◽  
Event Location ◽  
Location Methods

Locating microearthquake events below complex heterogeneous overburden requires robust location methodologies that can honor multipathing in the seismic wavefield. We have developed two full-waveform event location methods that form a complementary solution for locating earthquakes and simultaneously deriving focal mechanisms via moment tensor inversion. The methods are based on the application of 3D elastic wavefield modeling, which is used to generate waveforms and extract wavefield attributes, for comparison to the observed field data. Events are located and focal mechanisms are derived via a multiparameter inversion, which minimizes the differences between synthetic and observed data. The results have been applied to the induced seismicity observed within the giant Groningen gas field, onshore Netherlands, where recorded earthquakes are triggered by stress changes, induced in the reservoir through pressure depletion. Locating events below the field is compounded by the presence of strong guided waves, which are trapped in the lower velocity reservoir interval. This complex multivalued wavefield is problematic for traditional event location methods, which assume a single traveltime arrival. We overcome this limitation by using all event arrivals in a wave-based solution to improve the accuracy of locating earthquakes and overcome the ambiguity of solving for location and the focal mechanism simultaneously. The event location methods have been applied to shallow and deep monitoring networks, and 150 events have been located with high accuracy. The interpretation of the earthquake activity indicates that the events studied originate from the movement of larger graben bounding faults, which are oriented in a north-northwest–south-southeast direction.

scholarly journals Information Length as a Useful Index to Understand Variability in the Global Circulation

Mathematics ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 299 ◽  
Author(s):  
Eun-jin Kim ◽  
James Heseltine ◽  
Hanli Liu
Keyword(s):  
Climate Model ◽  
Traditional Approach ◽  
Essential Feature ◽  
Complex Form ◽  
Time Dependent ◽  
Spatial Gradient ◽  
Mean Values ◽  
Global Circulation ◽  
New Perspective ◽  
Non Gaussian

With improved measurement and modelling technology, variability has emerged as an essential feature in non-equilibrium processes. While traditionally, mean values and variance have been heavily used, they are not appropriate in describing extreme events where a significant deviation from mean values often occurs. Furthermore, stationary Probability Density Functions (PDFs) miss crucial information about the dynamics associated with variability. It is thus critical to go beyond a traditional approach and deal with time-dependent PDFs. Here, we consider atmospheric data from the Whole Atmosphere Community Climate Model (WACCM) and calculate time-dependent PDFs and the information length from these PDFs, which is the total number of statistically different states that a system evolves through in time. Specifically, we consider the three cases of sampling data to investigate the distribution of information (information budget) along the altitude and longitude to gain a new perspective of understanding variabilities, correlation among different variables and regions. Time-dependent PDFs are shown to be non-Gaussian in general; the information length tends to increase with the altitude albeit in a complex form; this tendency is more robust for flows/shears than temperature. Much similarity among flows and shears in the information length is also found in comparison with the temperature. This means a strong correlation among flows/shears because of their coupling through gravity waves in this particular WACCM model. We also find the increase of the information length with the latitude and interesting hemispheric asymmetry for flows/shears/temperature, with the tendency of anti-correlation (correlation) between flows/shears and temperature at high (low) latitude. These results suggest the importance of high latitude/altitude in the information budget in the Earth’s atmosphere, the spatial gradient of the information length being a useful proxy for information flow.

Present-day tectonic stress regime in Egypt and surrounding area based on inversion of earthquake focal mechanisms

2013 ◽  
Vol 81 ◽  
pp. 1-15 ◽  
Author(s):  
H.M. Hussein ◽  
K.M. Abou Elenean ◽  
I.A. Marzouk ◽  
I.M. Korrat ◽  
I.F. Abu El-Nader ◽  
...  
Keyword(s):  
Tectonic Stress ◽  
Focal Mechanisms ◽  
Surrounding Area ◽  
Stress Regime ◽  
Earthquake Focal Mechanisms

Earthquake focal mechanisms, deformation state, and seismotectonics of the Pamir-Tien Shan region, Central Asia

1995 ◽  
Vol 100 (B10) ◽  
pp. 20321-20343 ◽  
Author(s):  
Albert A. Lukk ◽  
Sergei L. Yunga ◽  
Vladimir I. Shevchenko ◽  
Michael W. Hamburger
Keyword(s):  
Central Asia ◽  
Focal Mechanisms ◽  
Tien Shan ◽  
Earthquake Focal Mechanisms ◽  
Deformation State

Seismic doublets and a complex seismic sequence controlled by the rotation of the Juan Fernández microplate

2021 ◽  
Author(s):  
Simone Cesca ◽  
Carla Valenzuela Malebrán ◽  
José Ángel López-Comino ◽  
Timothy Davis ◽  
Carlos Tassara ◽  
...  
Keyword(s):  
Source Parameters ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Joint Analysis ◽  
Seismic Sequence ◽  
Local Data ◽  
Study Region ◽  
Coulomb Stress Changes ◽  
Earthquake Source Parameters ◽  
Stress Changes

<p> A complex seismic sequence took place in 2014 at the Juan Fernández microplate, a small microplate located between Pacific, Nazca and Antarctica plates. Despite the remoteness of the study region and the lack of local data, we were able to resolve earthquake source parameters and to reconstruct the complex seismic sequence, by using modern waveform-based seismological techniques. The sequence started with an exceptional Mw 7.1-6.7 thrust – strike slip earthquake doublet, the first subevent being the largest earthquake ever recorded in the region and one of the few rare thrust earthquakes in a region otherwise characterized by normal faulting and strike slip earthquakes. The joint analysis of seismicity and focal mechanisms suggest the activation of E-W and NE-SW faults or of an internal curved pseudofault, which is formed in response to the microplate rotation, with alternation of thrust and strike-slip earthquakes. Seismicity migrated Northward in its final phase, towards the microplate edge, where a second doublet with uneven focal mechanisms occurred. The sequence rupture kinematics is well explained by Coulomb stress changes imparted by the first subevent. Our analysis show that compressional stresses, which have been mapped at the northern boundary of the microplate, but never accompanied by large thrust earthquakes, can be accommodated by the rare occurrence of large, impulsive, shallow thrust earthquakes, with a considerable tsunamigenic potential.</p>

Earthquake Focal Mechanisms in the New Madrid Seismic Zone

2014 ◽  
Vol 85 (2) ◽  
pp. 257-267 ◽  
Author(s):  
G. A. Johnson ◽  
S. P. Horton ◽  
M. Withers ◽  
R. Cox
Keyword(s):  
Focal Mechanisms ◽  
New Madrid Seismic Zone ◽  
Seismic Zone ◽  
Earthquake Focal Mechanisms ◽  
New Madrid
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