scholarly journals Rupture-dependent breakdown energy in fault models with thermo-hydro-mechanical processes

2020 ◽  
Author(s):  
Valère Lambert ◽  
Nadia Lapusta
Keyword(s):  
Material Property ◽  
Numerical Models ◽  
Slip Rate ◽  
Shear Cracks ◽  
Dynamic Rupture ◽  
Rupture Dynamics ◽  
Stress Changes ◽  
History Of ◽  
Thermal Pressurization ◽  
Pass Through

Abstract. Substantial insight into earthquake source processes has resulted from considering frictional ruptures analogous to cohesive-zone shear cracks from fracture mechanics. This analogy holds for slip-weakening representations of fault friction that encapsulate the resistance to rupture propagation in the form of breakdown energy, analogous to fracture energy, prescribed in advance as if it were a material property of the fault interface. Here, we use numerical models of earthquake sequences with enhanced weakening due to thermal pressurization of pore fluids to show how accounting for thermo-hydro-mechanical processes during dynamic shear ruptures makes breakdown energy rupture-dependent. We find that local breakdown energy is neither a constant material property nor uniquely defined by the amount of slip attained during rupture, but depends on how that slip is achieved through the history of slip rate and dynamic stress changes during the rupture process. As a consequence, the frictional breakdown energy of the same location along the fault can vary significantly in different earthquake ruptures that pass through. These results suggest the need for re-examining the assumption of pre-determined frictional breakdown energy common in dynamic rupture modeling and for better understanding of the factors that control rupture dynamics in the presence of thermo-hydro-mechanical processes.

scholarly journals Rupture-dependent breakdown energy in fault models with thermo-hydro-mechanical processes

Solid Earth ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 2283-2302
Author(s):  
Valère Lambert ◽  
Nadia Lapusta
Keyword(s):  
Material Property ◽  
Numerical Models ◽  
Slip Rate ◽  
Shear Cracks ◽  
Dynamic Rupture ◽  
Rupture Dynamics ◽  
Stress Changes ◽  
History Of ◽  
Thermal Pressurization ◽  
Pass Through

Abstract. Substantial insight into earthquake source processes has resulted from considering frictional ruptures analogous to cohesive-zone shear cracks from fracture mechanics. This analogy holds for slip-weakening representations of fault friction that encapsulate the resistance to rupture propagation in the form of breakdown energy, analogous to fracture energy, prescribed in advance as if it were a material property of the fault interface. Here, we use numerical models of earthquake sequences with enhanced weakening due to thermal pressurization of pore fluids to show how accounting for thermo-hydro-mechanical processes during dynamic shear ruptures makes breakdown energy rupture-dependent. We find that local breakdown energy is neither a constant material property nor uniquely defined by the amount of slip attained during rupture, but depends on how that slip is achieved through the history of slip rate and dynamic stress changes during the rupture process. As a consequence, the frictional breakdown energy of the same location along the fault can vary significantly in different earthquake ruptures that pass through. These results suggest the need to reexamine the assumption of predetermined frictional breakdown energy common in dynamic rupture modeling and to better understand the factors that control rupture dynamics in the presence of thermo-hydro-mechanical processes.

scholarly journals The role of aseismic slip in hydraulic fracturing–induced seismicity

2019 ◽  
Vol 5 (8) ◽  
pp. eaav7172 ◽  
Author(s):  
Thomas S. Eyre ◽  
David W. Eaton ◽  
Dmitry I. Garagash ◽  
Megan Zecevic ◽  
Marco Venieri ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Slip Rate ◽  
Aseismic Slip ◽  
Dynamic Rupture ◽  
Induced Earthquakes ◽  
Rock Composition ◽  
Injection Zone ◽  
In Situ Experiments ◽  
Stress Changes

Models for hydraulic fracturing–induced earthquakes in shales typically ascribe fault activation to elevated pore pressure or increased shear stress; however, these mechanisms are incompatible with experiments and rate-state frictional models, which predict stable sliding (aseismic slip) on faults that penetrate rocks with high clay or total organic carbon. Recent studies further indicate that the earthquakes tend to nucleate over relatively short injection time scales and sufficiently far from the injection zone that triggering by either poroelastic stress changes or pore pressure diffusion is unlikely. Here, we invoke an alternative model based on recent laboratory and in situ experiments, wherein distal, unstable regions of a fault are progressively loaded by aseismic slip on proximal, stable regions stimulated by hydraulic fracturing. This model predicts that dynamic rupture initiates when the creep front impinges on a fault region where rock composition favors dynamic and slip rate weakening behavior.

scholarly journals Dilation of subglacial sediment governs incipient surge motion in glaciers with deformable beds

2020 ◽  
Vol 476 (2238) ◽  
pp. 20200033 ◽  
Author(s):  
B. M. Minchew ◽  
C. R. Meyer
Keyword(s):  
Pore Water ◽  
Flow Model ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Slip Rate ◽  
Effective Pressure ◽  
Ice Flow ◽  
History Of ◽  
Glacier Surges ◽  
Geographical Clustering

Glacier surges are quasi-periodic episodes of rapid ice flow that arise from increases in slip rate at the ice–bed interface. The mechanisms that trigger and sustain surges are not well understood. Here, we develop a new model of incipient surge motion for glaciers underlain by sediments to explore how surges may arise from slip instabilities within a thin layer of saturated, deforming subglacial till. Our model represents the evolution of internal friction, porosity and pore water pressure within the till as functions of the rate and history of shear deformation, and couples the till mechanics to a simple ice-flow model. Changes in pore water pressure govern incipient surge motion, with less permeable till facilitating surging because dilation-driven reductions in pore water pressure slow the rate at which till tends towards a new steady state, thereby allowing time for the glacier to thin dynamically. The reduction of overburden (and thus effective) pressure at the bed caused by dynamic thinning of the glacier sustains surge acceleration in our model. The need for changes in both the hydromechanical properties of the till and the thickness of the glacier creates restrictive conditions for surge motion that are consistent with the rarity of surge-type glaciers and their geographical clustering.

scholarly journals Endoscopic Removal of a Press-Through Pack from the Anal Canal

2021 ◽  
pp. 137-141
Author(s):  
Ayaka Takasu ◽  
Takashi Ikeya ◽  
Katsuyuki Fukuda
Keyword(s):  
Small Intestine ◽  
Anal Canal ◽  
Large Intestine ◽  
Digital Rectal Examination ◽  
Anal Pain ◽  
Endoscopic Removal ◽  
Mild Dementia ◽  
Anal Fissures ◽  
History Of ◽  
Pass Through

The incidence of press-through pack (PTP) ingestion has been increasing. In many cases, the ingested PTP is lodged in the esophagus. Here, we report a case of endoscopic removal of a PTP from the anal canal. An 89-year-old man with mild dementia presented with a 3-day history of anal pain. On digital rectal examination, we felt a hard and sharp object, which could not be manually removed due to its shape. Therefore, it was removed endoscopically. We inserted an endoscope with a large-caliber soft oblique cap and observed the PTP in the anal canal. It was successfully removed using grasping forceps. The patient was stable, with only mild anal fissures, and no serious complications such as perforation and bleeding were observed. It is generally recognized that a PTP that reaches the large intestine is naturally expelled. Even if a PTP could pass through the pylorus or the small intestine, it could still be difficult to discharge naturally from the anus without discomfort or pain, as in this case.

Constraining the slip rate of Jurassic rift faults through the drowning history of a carbonate platform

Terra Nova ◽  
2021 ◽  
Author(s):  
Santantonio Massimo ◽  
Cipriani Angelo ◽  
Fabbi Simone ◽  
Meister Christian
Keyword(s):  
Carbonate Platform ◽  
Slip Rate ◽  
History Of

scholarly journals The cryptic seismic potential of blind faults revealed by off-fault geomorphology, Pichilemu, Chile.

2020 ◽  
Author(s):  
Julius Jara-Muñoz ◽  
Daniel Melnick ◽  
Anne Socquet ◽  
Joaquin Cortés-Aranda ◽  
Dominik Brill ◽  
...  
Keyword(s):  
Slip Rate ◽  
Active Regions ◽  
Seismic Hazards ◽  
Recurrence Time ◽  
Diagnostic Features ◽  
Seismic Potential ◽  
Megathrust Earthquakes ◽  
Marine Terraces ◽  
Stress Changes ◽  
Geomorphic Features

Abstract In seismically-active regions, mapping capable faults and estimating their recurrence time is the first step to assess seismic hazards. Fault maps are commonly based on geologic and geomorphic features evident at the surface; however, mapping blind faults and estimating their seismic potential is challenging because on-fault diagnostic features are absent. Here, we study the Pichilemu Fault in coastal Chile, unknown until it generated a M7.0 earthquake in 2010. The lack of evident surface faulting suggests a partly-hidden blind fault. Using off-fault deformed marine terraces, we estimate a slip-rate of 0.42 ± 0.04 m/ka, which when integrated with deformation estimated from satellite geodesy during the 2010 earthquake suggests a 2.5 ± 0.25 ka recurrence time for M6.6-6.9 extensional earthquakes. We propose that extension is associated with stress changes during megathrust earthquakes and accommodated by sporadic slip during upper-plate earthquakes. Our results have implications for assessing the seismic potential of cryptic faults along seismically-active coasts.

scholarly journals New constraints on the exhumation history of the western Tauern Window (European Alps) from thermochronology, thermokinematic modeling, and topographic analysis

2021 ◽  
Author(s):  
Reinhard Wolff ◽  
Ralf Hetzel ◽  
István Dunkl ◽  
Aneta A. Anczkiewicz
Keyword(s):  
Hanging Wall ◽  
Thermal Relaxation ◽  
Slip Rate ◽  
Normal Fault ◽  
European Alps ◽  
Valley Bottom ◽  
Topographic Analysis ◽  
Tauern Window ◽  
History Of ◽  
Exhumation History

AbstractThe Brenner normal fault bounds the Tauern Window to the west and accommodated a significant portion of the orogen-parallel extension in the Eastern Alps. Here, we use zircon (U–Th)/He, apatite fission track, and apatite (U–Th)/He dating, thermokinematic modeling, and a topographic analysis to constrain the exhumation history of the western Tauern Window in the footwall of the Brenner fault. ZHe ages from an E–W profile (parallel to the slip direction of the fault) decrease westwards from ~ 11 to ~ 8 Ma and suggest a fault-slip rate of 3.9 ± 0.9 km/Myr, whereas AFT and AHe ages show no spatial trends. ZHe and AFT ages from an elevation profile indicate apparent exhumation rates of 1.1 ± 0.7 and 1.0 ± 1.3 km/Myr, respectively, whereas the AHe ages are again spatially invariant. Most of the thermochronological ages are well predicted by a thermokinematic model with a normal fault that slips at a rate of 4.2 km/Myr between ~ 19 and ~ 9 Ma and produces 35 ± 10 km of extension. The modeling reveals that the spatially invariant AHe ages are caused by heat advection due to faulting and posttectonic thermal relaxation. The enigmatic increase of K–Ar phengite and biotite ages towards the Brenner fault is caused by heat conduction from the hot footwall to the cooler hanging wall. Topographic profiles across an N–S valley in the fault footwall indicate 1000 ± 300 m of erosion after faulting ceased, which agrees with the results of our thermokinematic model. Valley incision explains why the Brenner fault is located on the western valley shoulder and not at the valley bottom. We conclude that the ability of thermokinematic models to quantify heat transfer by rock advection and conduction is crucial for interpreting cooling ages from extensional fault systems.

Multicycle Simulation of Strike-Slip Earthquake Rupture for Use in Near-Source Ground-Motion Simulations

2021 ◽  
Author(s):  
Percy Galvez ◽  
Anatoly Petukhin ◽  
Paul Somerville ◽  
Jean-Paul Ampuero ◽  
Ken Miyakoshi ◽  
...  
Keyword(s):  
Ground Motion ◽  
Stress Drop ◽  
Slip Rate ◽  
Rupture Process ◽  
Earthquake Rupture ◽  
Rupture Velocity ◽  
Source Inversion ◽  
Dynamic Rupture ◽  
Wide Range ◽  
Source Scaling

ABSTRACT Realistic dynamic rupture modeling validated by observed earthquakes is necessary for estimating parameters that are poorly resolved by seismic source inversion, such as stress drop, rupture velocity, and slip rate function. Source inversions using forward dynamic modeling are increasingly used to obtain earthquake rupture models. In this study, to generate a large number of physically self-consistent rupture models, rupture process of which is consistent with the spatiotemporal heterogeneity of stress produced by previous earthquakes on the same fault, we use multicycle simulations under the rate and state (RS) friction law. We adopt a one-way coupling from multicycle simulations to dynamic rupture simulations; the quasidynamic solver QDYN is used to nucleate the seismic events and the spectral element dynamic solver SPECFEM3D to resolve their rupture process. To simulate realistic seismicity, with a wide range of magnitudes and irregular recurrence, several realizations of 2D-correlated heterogeneous random distributions of characteristic weakening distance (Dc) in RS friction are tested. Other important parameters are the normal stress, which controls the stress drop and rupture velocity during an earthquake, and the maximum value of Dc, which controls rupture velocity but not stress drop. We perform a parametric study on a vertical planar fault and generate a set of a hundred spontaneous rupture models in a wide magnitude range (Mw 5.5–7.4). We validate the rupture models by comparison of source scaling, ground motion (GM), and surface slip properties to observations. We compare the source-scaling relations between rupture area, average slip, and seismic moment of the modeled events with empirical ones derived from source inversions. Near-fault GMs are computed from the source models. Their peak ground velocities and peak ground accelerations agree well with the ground-motion prediction equation values. We also obtain good agreement of the surface fault displacements with observed values.

scholarly journals A physics-based approach of deep interseismic creep for viscoelastic strike-slip earthquake cycle models

2019 ◽  
Vol 220 (1) ◽  
pp. 79-95
Author(s):  
Lucile Bruhat
Keyword(s):  
Surface Deformation ◽  
Slip Rate ◽  
Strike Slip ◽  
Dynamic Rupture ◽  
Crust And Upper Mantle ◽  
Slip Rates ◽  
Region I ◽  
Best Fitting ◽  
Time Invariant ◽  
Analytical Expressions

SUMMARY Most geodetic inversions of surface deformation rates consider the depth distribution of interseismic fault slip-rate to be time invariant. However, some numerical simulations show downdip penetration of dynamic rupture into regions with velocity-strengthening friction, with subsequent updip propagation of the locked-to-creeping transition. Recently, Bruhat and Segall developed a new method to characterize interseismic slip rates, that allows slip to penetrate up dip into the locked region. This simple model considered deep interseismic slip as a crack loaded at its downdip end, and provided analytical expressions for stress drop within the crack, slip and slip rate along the fault. This study extends this approach to strike-slip fault environments, and includes coupling of creep to viscoelastic flow in the lower crust and upper mantle. I use this model to investigate interseismic deformation rates along the Carrizo Plain section of the San Andreas fault. This study reviews possible models, elastic and viscoelastic, for fitting horizontal surface rates. Using this updated approach, I develop a physics-based solution for deep interseismic creep which accounts for possible slow vertical propagation, and investigate how it improves the fit of the horizontal deformation rates in the Carrizo Plain region. I found solutions for fitting the surface deformation rates that allow for reasonable estimates for earthquake rupture depth and coseismic displacement and improves the overall fit to the data. Best-fitting solutions present half-space relaxation time around 70 yr, and very low propagation speeds, less than a metre per year, suggesting a lack of creep propagation.

scholarly journals The “mule” with golden eggs: Retrieval of unusual foreign body

2015 ◽  
Vol 06 (02) ◽  
pp. 079-080
Author(s):  
Chhavi Wadhwa ◽  
Shibumon Madhavan ◽  
Alfred J. Augustine ◽  
Suresh Shenoy ◽  
Abid Mirza
Keyword(s):  
Foreign Body ◽  
Foreign Bodies ◽  
Gi Tract ◽  
Unusual Foreign Body ◽  
Upper Gi ◽  
Intentional Ingestion ◽  
History Of ◽  
Upper Gi Endoscopy ◽  
Pass Through ◽  
Body Packers

AbstractForeign body ingestions often consist of benign objects that will readily pass through the gastrointestinal (GI) tract without necessitating further intervention. There are various reports in the literature about intentional ingestion of foreign bodies in prisoners and body packers, which required intervention. We present a case of 44-year-old male with a history of intentional ingestion of 30 gold pellets as a carrier from Dubai to India. The pellets were successfully retrieved by upper GI endoscopy after 1-week of observation and unsuccessful attempts of conservative trial. There have been many foreign body extractions but gold retrieval has been a rare case.

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