scholarly journals Characteristics of earthquake ruptures and dynamic off-fault deformation on propagating faults

Solid Earth ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 1333-1360 ◽  
Author(s):  
Simon Preuss ◽  
Jean Paul Ampuero ◽  
Taras Gerya ◽  
Ylona van Dinther
Keyword(s):  
Stress Field ◽  
Damage Zone ◽  
Finite Depth ◽  
Dependent Measure ◽  
Seismogenic Zone ◽  
Earthquake Ruptures ◽  
Fault Deformation ◽  
Aseismic Deformation ◽  
Fault Growth

Abstract. Natural fault networks are geometrically complex systems that evolve through time. The evolution of faults and their off-fault damage patterns are influenced by both dynamic earthquake ruptures and aseismic deformation in the interseismic period. To better understand each of their contributions to faulting we simulate both earthquake rupture dynamics and long-term deformation in a visco-elasto-plastic crust subjected to rate- and state-dependent friction. The continuum mechanics-based numerical model presented here includes three new features. First, a 2.5-D approximation is created to incorporate the effects of a viscoelastic lower crustal substrate below a finite depth. Second, we introduce a dynamically adaptive (slip-velocity-dependent) measure of fault width to ensure grid size convergence of fault angles for evolving faults. Third, fault localization is facilitated by plastic strain weakening of bulk rate and state friction parameters as inspired by laboratory experiments. This allows us to simulate sequences of episodic fault growth due to earthquakes and aseismic creep for the first time. Localized fault growth is simulated for four bulk rheologies ranging from persistent velocity weakening to velocity strengthening. Interestingly, in each of these bulk rheologies, faults predominantly localize and grow due to aseismic deformation. Yet, cyclic fault growth at more realistic growth rates is obtained for a bulk rheology that transitions from velocity-strengthening friction to velocity-weakening friction. Fault growth occurs under Riedel and conjugate angles and transitions towards wing cracks. Off-fault deformation, both distributed and localized, is typically formed during dynamic earthquake ruptures. Simulated off-fault deformation structures range from fan-shaped distributed deformation to localized splay faults. We observe that the fault-normal width of the outer damage zone saturates with increasing fault length due to the finite depth of the seismogenic zone. We also observe that dynamically and statically evolving stress fields from neighboring fault strands affect primary and secondary fault growth and thus that normal stress variations affect earthquake sequences. Finally, we find that the amount of off-fault deformation distinctly depends on the degree of optimality of a fault with respect to the prevailing but dynamically changing stress field. Typically, we simulate off-fault deformation on faults parallel to the loading direction. This produces a 6.5-fold higher off-fault energy dissipation than on an optimally oriented fault, which in turn has a 1.5-fold larger stress drop. The misalignment of the fault with respect to the static stress field thus facilitates off-fault deformation. These results imply that fault geometries bend, individual fault strands interact, and optimal orientations and off-fault deformation vary through space and time. With our work we establish the basis for simulations and analyses of complex evolving fault networks subject to both long-term and short-term dynamics.

scholarly journals Characteristics of earthquake ruptures and dynamic off-fault deformation on propagating faults

2020 ◽  
Author(s):  
Simon Preuss ◽  
Jean Paul Ampuero ◽  
Taras Gerya ◽  
Ylona van Dinther
Keyword(s):  
Stress Field ◽  
Damage Zone ◽  
Finite Depth ◽  
Dependent Measure ◽  
Seismogenic Zone ◽  
Earthquake Ruptures ◽  
Fault Deformation ◽  
Aseismic Deformation ◽  
Fault Growth

Abstract. Natural fault networks are geometrically complex systems that evolve through time. The evolution of faults and their off-fault damage pattern are influenced by both dynamic earthquake ruptures and aseismic deformation in the interseismic period. To better understand each of their contributions to faulting we simulate both earthquake rupture dynamics and long-term deformation in a visco-elasto-plastic crust subjected to rate-and-state-dependent friction. The continuum mechanics-based numerical model presented here includes three new features. First, a 2.5-D approximation to incorporate effects of a viscoelastic lower crustal substrate below a finite depth. Second, we introduce a dynamically adaptive (slip-velocity-dependent) measure of fault width to ensure grid size convergence of fault angles for evolving faults. Third, fault localization is facilitated by plastic strain weakening of bulk rate-and-state friction parameters as inspired by laboratory experiments. This allows us to for the first time simulate sequences of episodic fault growth due to earthquakes and aseismic creep. Localized fault growth is simulated for four bulk rheologies ranging from persistent velocity-weakening to velocity-strengthening. Interestingly, in each of these bulk rheologies, faults predominantly localize and grow due to aseismic deformation. Yet, cyclic fault growth at more realistic growth rates is obtained for a bulk rheology that transitions from velocity-strengthening friction to velocity-weakening friction. Fault growth occurs under Riedel and conjugate angles and transitions towards wing cracks. Off-fault deformation, both distributed and localized, is typically formed during dynamic earthquake ruptures. Simulated off-fault deformation structures range from fan-shaped distributed deformation to localized Riedel splay faults. We observe that the fault-normal width of the outer damage zone saturates with increasing fault length due to the finite depth of the seismogenic zone. We also observe that dynamically and statically evolving stress fields from neighboring fault strands affect primary and secondary fault growth and thus that normal stress variations affect earthquake sequences. Finally, we find that the amount of off-fault deformation distinctly depends on the degree of optimality of a fault with respect to the prevailing but dynamically changing stress field. Typically, we simulate off-fault deformation on faults parallel to the loading direction. This produces a 6.5-fold higher off-fault energy dissipation than on an optimally oriented fault, which in turn has a 1.5-fold larger stress drop. The misalignment of the fault with respect to the static stress field thus facilitates off-fault deformation. These results imply that fault geometries bend, individual fault strands interact and that optimal orientations and off-fault deformation vary through space and time. With our work we establish the basis for simulations and analyses of complex evolving fault networks subject to both long-term and short-term dynamics.

Characteristics of episodic fault growth and off-fault deformation structures

2020 ◽  
Author(s):  
Simon Preuss ◽  
Jean Paul Ampuero ◽  
Luca Dal Zilio ◽  
Taras Gerya ◽  
Ylona van Dinther
Keyword(s):  
Stress Field ◽  
Damage Zone ◽  
Finite Depth ◽  
Seismogenic Zone ◽  
Deformation Structures ◽  
Earthquake Ruptures ◽  
Fault Deformation ◽  
Aseismic Deformation ◽  
Fault Growth

<p>Natural fault networks are geometrically complex systems that evolve through time. The growth and evolution of faults and their off-fault damage pattern are influenced by both dynamic earthquake ruptures and aseismic deformation during the interseismic period. To better understand each of their contributions to faulting we simulate both earthquake rupture dynamics and long-term deformation in a visco-elasto-plastic crust subjected to rate-and-state-dependent friction [1,2]. The continuum mechanics-based numerical model presented here includes three new features. First, a 2.5-D approximation to incorporate effects of a viscoelastic lower crustal substrate below a finite depth. Second, we introduce a dynamically adaptive (slip-velocity-dependent) measure of fault width to ensure grid size convergence of fault angles for evolving faults. Third, fault localisation is facilitated by plastic strain weakening of bulk rate-and-state friction parameters as motivated by laboratory experiments. This allows us to for the first time simulate sequences of episodic fault growth due to earthquakes and aseismic creep. Localized fault growth is simulated for four bulk rheologies ranging from persistent velocity-weakening to velocity-strengthening. Yet, episodic fault growth is only obtained for a bulk rheology that transitions from velocity-strengthening friction to velocity-weakening friction. Interestingly, in each of these bulk rheologies, faults predominantly localise [LDZ1] and grow in the inter-seismic period due to aseismic deformation. However, [LDZ2] off-fault deformation - both distributed and localised - is typically formed during dynamic earthquake ruptures. Simulated off-fault deformation structures range from fan-shaped distributed deformation to localized Riedel splay faults and antithetic conjugate [LDZ3] Riedel shear faults [LDZ4] and towards wing cracks. We observe that the fault-normal width of the outer damage zone saturates with increasing fault length due to the finite depth of the seismogenic zone. We also observe that dynamically and statically evolving stress fields from neighbouring fault strands affects first and secondary fault growth. Finally, we find that the amount of off-fault deformation distinctly depends on the degree of optimality of a fault with respect to the prevailing but dynamically changing stress field. Typically, we simulate off-fault deformation on faults parallel to the loading direction. This produces a 6.5-fold higher off-fault energy dissipation than on an optimally oriented fault, which in turn has a 1.5-fold larger stress drop. The misalignment of the fault with respect to the static stress field thus facilitates off-fault deformation. These results imply that fault geometries bend [2], individual fault strands interact and that optimal orientations and off-fault deformation vary through space and time. With our work we establish the basis for simulations and analyses of complex evolving fault networks subject to both long-term and short-term dynamics. Currently, we are using this basis to simulate and explain orthogonal faulting observed in the 2019 M6.4-M7.1 Ridgecrest earthquake sequence.</p>

scholarly journals Marmara Island earthquakes, of 1265 and 1935; Turkey

2006 ◽  
Vol 6 (6) ◽  
pp. 999-1006 ◽  
Author(s):  
Y. Altınok ◽  
B. Alpar
Keyword(s):  
Fault Zones ◽  
Marmara Sea ◽  
Sea Waves ◽  
Rock Falls ◽  
The West ◽  
Moderate Size ◽  
Northwestern Turkey ◽  
Earthquake Ruptures ◽  
Fundamental Understanding

Abstract. The long-term seismicity of the Marmara Sea region in northwestern Turkey is relatively well-recorded. Some large and some of the smaller events are clearly associated with fault zones known to be seismically active, which have distinct morphological expressions and have generated damaging earthquakes before and later. Some less common and moderate size earthquakes have occurred in the vicinity of the Marmara Islands in the west Marmara Sea. This paper presents an extended summary of the most important earthquakes that have occurred in 1265 and 1935 and have since been known as the Marmara Island earthquakes. The informative data and the approaches used have therefore the potential of documenting earthquake ruptures of fault segments and may extend the records kept on earthquakes far before known history, rock falls and abnormal sea waves observed during these events, thus improving hazard evaluations and the fundamental understanding of the process of an earthquake.

Study on the long-term behaviour of glass fibre in the tensile stress field

2019 ◽  
Vol 45 (9) ◽  
pp. 11578-11583 ◽  
Author(s):  
Dapeng Wang ◽  
Qingzhao Wang ◽  
Zhiming Wang ◽  
Huanying Jiang ◽  
Zhao Zhang ◽  
...  
Keyword(s):  
Stress Field ◽  
Tensile Stress ◽  
Glass Fibre ◽  
Tensile Stress Field

Hydromechanical response of a bedded argillaceous rock formation to excavation and water injection

2015 ◽  
Vol 52 (1) ◽  
pp. 1-17 ◽  
Author(s):  
A.D. Le ◽  
T.S. Nguyen
Keyword(s):  
Rock Mass ◽  
Pore Pressure ◽  
Damage Zone ◽  
Water Injection ◽  
Constitutive Relationship ◽  
Opalinus Clay ◽  
Anisotropic Plastic ◽  
Mont Terri ◽  
Excavation Damage

Opalinus clay is a candidate host formation for the geological disposal of nuclear wastes in Switzerland. The understanding of its long-term mechanical (M) and hydraulic (H) behaviour is an essential requirement for the assessment of its performance as a barrier against radionuclide transport. To study the HM response of Opalinus clay, a microtunnel, 13 m in length and 1 m in diameter, was excavated in that formation at the Mont Terri Underground Research Facility. The rock mass was equipped with sensors to measure the deformation and pore pressure in the rock mass during and after the excavation. A mathematical model that couples the equations of flow and mechanical equilibrium was developed to simulate the HM response of the rock mass. An anisotropic plastic constitutive relationship, based on a microstructure tensor approach, was incorporated in the model. Creep was also considered, as well as the anisotropy of permeability. It is shown that the model satisfactorily predicts the shape and extent of the excavation damage zone (EDZ), deformation, and pore pressure in the rock mass. It is also shown that anisotropy and creep play an important role in the HM response of the rock mass to excavation. The model was further used to simulate water injection tests performed at the test section in the microtunnel. The results show that EDZ, due to its high permeability, is a preferential groundwater flow path along the microtunnel.

Physical and chemical strain-hardening during faulting in poorly lithified sandstone: The role of kinematic stress field and selective cementation

2019 ◽  
Vol 132 (5-6) ◽  
pp. 1183-1200 ◽  
Author(s):  
Mattia Pizzati ◽  
Fabrizio Balsamo ◽  
Fabrizio Storti ◽  
Paola Iacumin
Keyword(s):  
Stress Field ◽  
Strain Hardening ◽  
Fault Zone ◽  
Deformation Band ◽  
Early Stage ◽  
Damage Zone ◽  
Isotope Analysis ◽  
Deformation Bands ◽  
Multidisciplinary Study ◽  
Diagenetic Evolution

Abstract In this work, we report the results of a multidisciplinary study describing the structural architecture and diagenetic evolution of the Rocca di Neto extensional fault zone developed in poorly lithified sandstones of the Crotone Basin, Southern Italy. The studied fault zone has an estimated displacement of ∼90 m and consists of: (1) a low-deformation zone with subsidiary faults and widely spaced deformation bands; (2) an ∼10-m-wide damage zone, characterized by a dense network of conjugate deformation bands; (3) an ∼3-m-wide mixed zone produced by tectonic mixing of sediments with different grain size; (4) an ∼1-m-wide fault core with bedding transposed into foliation and ultra-comminute black gouge layers. Microstructural investigations indicate that particulate flow was the dominant early-stage deformation mechanism, while cataclasis became predominant after porosity loss, shallow burial, and selective calcite cementation. The combination of tectonic compaction and preferential cementation led to a strain-hardening behavior inducing the formation of “inclined conjugate deformation band sets” inside the damage zone, caused by the kinematic stress field associated with fault activity. Conversely, conjugate deformation band sets with a vertical bisector formed outside the damage zone in response to the regional extensional stress field. Stable isotope analysis helped in constraining the diagenetic environment of deformation, which is characterized by mixed marine-meteoric signature for cements hosted inside the damage zone, while it progressively becomes more meteoric moving outside the fault zone. This evidence supports the outward propagation of fault-related deformation structures in the footwall damage zone.

Long-term representations of melodies in Western listeners: Influences of familiarity, musical expertise, tempo and structure

2016 ◽  
Vol 45 (5) ◽  
pp. 665-681 ◽  
Author(s):  
Niklas Büdenbender ◽  
Gunter Kreutz
Keyword(s):  
Stimulus Presentation ◽  
Dependent Measure ◽  
Musical Expertise ◽  
Musical Tempo ◽  
Age Range ◽  
Gating Paradigm

We investigated the effects of familiarity, level of musical expertise, musical tempo, and structural boundaries on the identification of familiar and unfamiliar tunes. Healthy Western listeners ( N = 62; age range 14–64 years) judged their level of familiarity with a preselected set of melodies when the number of tones of a given melody was increased from trial to trial according to the so-called gating paradigm. The number of tones served as one dependent measure. The second dependent measure was the physical duration of the stimulus presentation until listeners identified a melody as familiar or unfamiliar. Results corroborate previous work, suggesting that listeners need less information to recognize familiar as compared to unfamiliar melodies. Both decreasing and increasing the original tempo by a factor of two delayed the identification of familiar melodies. Furthermore, listeners had more difficulty identifying unfamiliar melodies when tempo was increased. Finally, musical expertise significantly influenced identification of either melodic category, i.e., reducing the required number of tones. Taken together, the findings support theories which suggest that tempo information is coded in melody representation, and that musical expertise is associated with especially efficient strategies for accessing long-term representations of melodic materials.

scholarly journals The IODP Expedition 332 : Eyes on the Prism, The NanTroSEIZE Observatories

2012 ◽  
Vol 14 ◽  
pp. 34-38 ◽  
Author(s):  
S. T. Toczko ◽  
A. J. Kopf ◽  
E. Araki ◽  
Keyword(s):  
Nankai Trough ◽  
Temperature Data ◽  
Seismogenic Zone ◽  
Plate Boundaries ◽  
Transient Pressure ◽  
Ocean Drilling Program ◽  
Ocean Drilling ◽  
Integrated Ocean Drilling Program ◽  
Drilling Project

The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is a major long-term drilling project designed to investigate the seismogenic behavior of subduction zone plate boundaries. Integrated Ocean Drilling Program (IODP) Expedition 332 deployed a long-term borehole monitoring system (LTBMS), an advanced Circulation Obviation Retrofit Kit (CORK)-type observatory. The recovery of pressure and temperature data from a temporary observatory (SmartPlug) deployed during IODP Expedition 319 helped prove the SmartPlug concept. The permanent LTBMS was deployed n the upper 1000 m of Site C0002, while the SmartPlug was recovered from Site C0010 and replaced with a more capable "GeniusPlug", incorporating an extension with a geochem-ical sampler and biological experiment to the original SmartPlug design. SmartPlug pressure and temperature data showed signs of transient pressure events. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.14.04.2012" target="_blank">10.2204/iodp.sd.14.04.2012</a>

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