scholarly journals Observations of Aseismic Slip Driven by Fluid Pressure Following the 2016 Kaikōura, New Zealand, Earthquake

2018 ◽  
Vol 45 (20) ◽  
Author(s):  
Ian J. Hamling ◽  
Phaedra Upton
Keyword(s):  
New Zealand ◽  
Fluid Pressure ◽  
Aseismic Slip

scholarly journals Focused fluid seepage related to variations in accretionary wedge structure, Hikurangi margin, New Zealand

Geology ◽  
2019 ◽  
Vol 48 (1) ◽  
pp. 56-61 ◽  
Author(s):  
Sally J. Watson ◽  
Joshu J. Mountjoy ◽  
Philip M. Barnes ◽  
Gareth J. Crutchley ◽  
Geoffroy Lamarche ◽  
...  
Keyword(s):  
Fluid Flow ◽  
New Zealand ◽  
Fluid Pressure ◽  
Data Sets ◽  
Accretionary Wedge ◽  
Fault Mechanics ◽  
Spatial Coverage ◽  
Fluid Seepage ◽  
Pressure Regime ◽  
Subduction Setting

Abstract Hydrogeological processes influence the morphology, mechanical behavior, and evolution of subduction margins. Fluid supply, release, migration, and drainage control fluid pressure and collectively govern the stress state, which varies between accretionary and nonaccretionary systems. We compiled over a decade of published and unpublished acoustic data sets and seafloor observations to analyze the distribution of focused fluid expulsion along the Hikurangi margin, New Zealand. The spatial coverage and quality of our data are exceptional for subduction margins globally. We found that focused fluid seepage is widespread and varies south to north with changes in subduction setting, including: wedge morphology, convergence rate, seafloor roughness, and sediment thickness on the incoming Pacific plate. Overall, focused seepage manifests most commonly above the deforming backstop, is common on thrust ridges, and is largely absent from the frontal wedge despite ubiquitous hydrate occurrences. Focused seepage distribution may reflect spatial differences in shallow permeability architecture, while diffusive fluid flow and seepage at scales below detection limits are also likely. From the spatial coincidence of fluids with major thrust faults that disrupt gas hydrate stability, we surmise that focused seepage distribution may also reflect deeper drainage of the forearc, with implications for pore-pressure regime, fault mechanics, and critical wedge stability and morphology. Because a range of subduction styles is represented by 800 km of along-strike variability, our results may have implications for understanding subduction fluid flow and seepage globally.

Episodic fluid pressure cycling controls earthquake sequences on subduction megathrusts

2021 ◽  
Author(s):  
Luca Dal Zilio ◽  
Taras Gerya
Keyword(s):  
Fluid Flow ◽  
Finite Difference Methods ◽  
Fluid Pressure ◽  
Seismogenic Zone ◽  
Slow Slip ◽  
Aseismic Slip ◽  
Earthquake Physics ◽  
Megathrust Earthquakes ◽  
Pressure Cycling ◽  
Crustal Stresses

<p>A major goal in earthquake physics is to derive a constitutive framework for fault slip that captures the dependence of friction on lithology, sliding velocity, temperature, and pore fluid pressure. Here, we present a newly-developed two-phase flow numerical model — which couples solid rock deformation and pervasive fluid flow — to show how crustal stresses and fluid pressures within subducting megathrust evolve before and during slow slip and fast events. This unified 2D numerical framework couples inertial mechanical deformation and fluid flow by using finite difference methods, marker-in-cell technique, and poro-visco-elasto-plastic rheology. An adaptive time stepping allows the correct resolution of both long- and short-time scales, ranging from years to milliseconds during the dynamic propagation of dynamic rupture.</p><p>We investigate how permeability and its spatial distribution control the interseismic coupling along the megathrust interface, the interplay between seismic and aseismic slip, and the nucleation of large earthquakes. While a constant permeability leads to more regular seismic cycles, a depth dependent permeability contributes substantially to the development of two distinct megathrust zones: a shallow, locked seismogenic zone and a deep, narrow aseismic segment characterized by slow-slip events. Furthermore, we show that without requiring any specific friction law, our models reveal that permeability, episodic stress transfer and fluid pressure cycling control the predominant slip mode along the subduction megathrust. Furthermore, we analyze how rate dependent strength and dilatation affect rupture propagation and arrest. Our preliminary results show that fluid-solid poro-visco-elasto-plastic coupling behaves similarly to rate- and state-dependent friction. In this context, fluid pressure plays the role of state parameter whose time evolution is governed by: (i) the short-term elasto-plastic collapse of pores inside faults during the rupture (coseismic self-pressurization of faults) and (ii) the long-term pore-pressure diffusion from the faults into surrounding rocks (post- and interseismic relaxation of fluid pressure). This newly-developed numerical framework contributes to improve our understanding of the physical mechanisms underlying large megathrust earthquakes, and demonstrate that fluid play a key role in controlling the interplay between seismic and aseismic slip.</p>

scholarly journals Fluid budgets along the northern Hikurangi subduction margin, New Zealand: the effect of a subducting seamount on fluid pressure

2015 ◽  
Vol 202 (1) ◽  
pp. 277-297 ◽  
Author(s):  
Susan Ellis ◽  
Åke Fagereng ◽  
Dan Barker ◽  
Stuart Henrys ◽  
Demian Saffer ◽  
...  
Keyword(s):  
New Zealand ◽  
Fluid Pressure

Episodic fluid pressure cycling controls the interplay between Slow Slip Events and Large Megathrust Earthquakes

2020 ◽  
Author(s):  
Claudio Petrini ◽  
Luca Dal Zilio ◽  
Taras Gerya
Keyword(s):  
Fluid Flow ◽  
Subduction Zones ◽  
Finite Difference Methods ◽  
Fluid Pressure ◽  
Slow Slip ◽  
Aseismic Slip ◽  
Slow Slip Events ◽  
Megathrust Earthquakes ◽  
Pressure Cycling ◽  
Crustal Stresses

<p>Slow slip events (SSEs) are part of a spectrum of aseismic processes that relieve tectonic stress on faults. Their occurrence in subduction zones have been suggested to trigger megathrust earthquakes due to perturbations in fluid pressure. However, examples to date have been poorly recorded and physical observations of temporal fluid pressure fluctuations through slow slip cycles remain elusive. Here, we use a newly developed two-phase flow numerical model — which couples solid rock deformation and pervasive fluid flow — to show how crustal stresses and fluid pressures within subducting megathrust evolve before and during slow slip and regular events. This unified 2D numerical framework couples inertial mechanical deformation and fluid flow by using finite difference methods, marker-in-cell technique, and poro-visco-elasto-plastic rheologies. Furthermore, an adaptive time stepping allows the correct resolution of both long- and short-time scales, ranging from years to milliseconds during the dynamic propagation of earthquake rupture.</p><p>Here we show how permeability and its spatial distribution control the degree of locking along the megathrust interface and the interplay between seismic and aseismic slip. While a constant permeability leads to more regular seismic cycles, a depth dependent permeability contributes substantially to the development of two distinct megathrust zones: a shallow, locked seismogenic zone and a deep, narrow aseismic segment characterized by SSEs. Furthermore, we show that without requiring any specific friction law, our model shows that permeability, episodic stress transfer and fluid pressure cycling control the predominant slip mode along the subduction megathrust. Specifically, we find that the up-dip propagation of episodic SSEs systematically decreases the fault strength due to a continuous accumulation and release of fluid pressure within overpressured subducting interface, thus affecting the timing of large megathrust earthquakes. These results contribute to improve our understanding of the physical driving forces underlying the interplay between seismic and aseismic slip, and demonstrate that slow slip events may prove useful for short-term earthquake forecasts.</p>

Low seismic-wave speeds and enhanced fluid pressure beneath the Southern Alps of New Zealand

Geology ◽  
2001 ◽  
Vol 29 (8) ◽  
pp. 679 ◽  
Author(s):  
Tim Stern ◽  
Stefan Kleffmann ◽  
David Okaya ◽  
Martin Scherwath ◽  
Stephen Bannister
Keyword(s):  
New Zealand ◽  
Seismic Wave ◽  
Fluid Pressure ◽  
Southern Alps ◽  
Wave Speeds

scholarly journals Microseismicity of the Central Alpine Fault Region, New Zealand

2021 ◽  
Author(s):  
◽  
Bronwyn Cherie O'Keefe
Keyword(s):  
New Zealand ◽  
High Stress ◽  
Fluid Pressure ◽  
Time Frame ◽  
B Value ◽  
Point Sources ◽  
Local Magnitude ◽  
Linear Inversion ◽  
Alpine Fault ◽  
Brittle Ductile Transition

<p>This study investigates the spatial and temporal patterns in microseismicity along the central section of the Alpine Fault, South Island, New Zealand. This section, between Harihari and Karangarua, has significantly lower seismicity than the regions to the northeast and southwest. Several hypotheses of mechanisms said to contribute to the anomaly have been proposed over the years including locked fault, slow slip, shallow creep and external fluids affecting the thermal regime and brittle-ductile transition. Focussing on the shallow crust, the contrasting seismic character is compared to the northern and southern sections from seismicity behaviour, focal mechanisms and seismogenic depth. A temporal array of eight seismographs (including three broadband instruments) was augmented with three GeoNet stations bounding the array. This provided an average spacing of 14 km and a magnitude cut-off of ML 1.6 compared to the GeoNet national network cut-off of ML 2.6 and station spacing of 80-100 km. The Gutenberg-Richter distribution for the four month time frame analysed defned a b-value of 0.75 plus or minus 0.06 which may indicate a locked, heterogeneous zone under high-stress from fluid pressure or a predominance of thrust mechanisms over the survey period. Seismicity over the deployment was within the average range of the last 15 years. The 'horseshoe' shaped seismicity pattern observed from long-term national catologue data is similar for smaller magnitudes. While the central portion of the Alpine Fault is quieter with unusually low b-value, the region is not aseismic. Neither does it experience the level of microseismicity seen in creeping faults. The brittle-ductile transition varies laterally along the fault and is estimated at up to 15 km for most of the survey region but closer to 10 km for the region associated with the highest orogenic uplift rates which compares well with past studies. A local magnitude scale was developed from direct linear inversion of the pseudoWood-Anderson amplitudes and event-station distances. A linear inversion of data from the standard New Zealand magnitude equation characterised an attenuation parameter of 0.0167 km minus 1; more than double the value used in national local magnitude calculations (of 0.0067 km minus 1). Swarm clustering dominates the seismicity character of the time frame. Utilising the earthquake relocation program HypoDD, a selection of clusters both near the Alpine Fault and away from it resolve to point sources. Those close to the Alpine Fault are located in what may be the footwall of the Fault which may indicate that the velocity model has located the events too far to the northwest.</p>

Dual seismic migration velocities reveal imbricated fluid diffusion and aseismic slip In a Corinth Gulf  swarm (Greece)

2021 ◽  
Author(s):  
Louis De Barros ◽  
Pierre Dublanchet ◽  
Frédéric Cappa ◽  
Anne Deschamps
Keyword(s):  
Temporal Evolution ◽  
Fluid Pressure ◽  
Normal Fault ◽  
Mechanical Modeling ◽  
Aseismic Slip ◽  
Seismic Migration ◽  
Corinth Gulf ◽  
The Mean ◽  
Earthquake Sequences ◽  
Fluid Diffusion

&lt;p&gt;Fluid induced earthquake sequences generally appear as expanding swarms activating a particular fault. Such swarms are generally interpreted as fluid diffusion, which ignores the possibility of static, dynamic or aseismic triggering, and the existence of rapid migration. Here, we study the temporal evolution of a seismic swarm that occurred over a 10-day period in October 2015 in the extensional rift of the Corinth Gulf (Greece) using high-resolution earthquakes relocations. The seismicity radially migrates on a normal fault at a fluid diffusion velocity (~125 m/day). However, this migration occurs intermittently, with periods of fast expansion (2-to-10 km/day) during short seismic bursts alternating with quiescent periods. Moreover, the growing phases of the swarm illuminate a high number of repeaters. Therefore, we propose a new model to explain the combination of multiple driving processes for such swarms.&amp;#160; Fluid up flow in the fault may induce aseismic slip episodes, separated by phases of fluid pressure build-up. The stress perturbation due to aseismic slip may activate small asperities in the fault that produce bursts of seismicity during the most intense phase of the swarm. We then validated this model through hydro-mechanical modeling, where earthquakes consist in the failure of asperities on a creeping fault infiltrated by fluid. For that, we couple rate&amp;#8208;and&amp;#8208;state friction, non&amp;#8208;linear diffusivity and elasticity along a 1D interface. This model reproduces the dual migration speeds observed in real swarms. We show that migration speeds increase linearly with the mean pressurization, and are not dependent on the hydraulic diffusivity, as traditionally suggested.&lt;/p&gt;

Impact of dilatant strengthening and energy dissipation on fault slip stability

2021 ◽  
Author(s):  
Antoine Jacquey ◽  
Manolis Veveakis ◽  
Ruben Juanes
Keyword(s):  
Energy Dissipation ◽  
Fluid Pressure ◽  
Fault Slip ◽  
Numerical Continuation ◽  
Dissipated Energy ◽  
Dynamic Evolution ◽  
Coupling Scheme ◽  
Aseismic Slip ◽  
Stick Slip ◽  
The Stability

&lt;p&gt;The temporal and spatial distribution of fluid pressure and temperature within a fault core are key determinants of the onset and nature (seismic or aseismic) of fault slip. Laboratory and field&amp;#160;observations indicate that transient localization of fluid pressure and temperature often go hand in hand with strain localization upon seismic rupture: as slip occurs on a fault plane, temperature increases due to dissipated energy and fluid pressure decreases due to dilatant strengthening. An accurate description of this thermo-hydro-mechanical multiphysics coupling controlling slip mechanisms is therefore essential to characterize the stability of fault slip.&lt;/p&gt;&lt;p&gt;Here, we present results from analytical and numerical analyses of the stability of fault slip adopting a thermo-hydro-mechanical coupling scheme together with a rate-dependent plasticity formulation. In particular, we focus on the relevance of dilatant strengthening competing with energy dissipation as driving processes for stick-slip events and aseismic slip.&amp;#160;We analyze the multiple steady states of the system and their respective stability by means of a numerical continuation technique, and we describe the dynamic evolution of deformation, fluid pressure and temperature fields by considering an associated transient problem.&lt;/p&gt;&lt;p&gt;The results presented here provide insights into the stability criterion for aseismic slip and the dynamic evolution of slip instability as a function of the physical (thermal and hydraulic) properties of the fault material and the boundary conditions (tectonic stresses and off-fault fluid pressure and temperature conditions). We identify two mechanisms for periodic slip, one driven by elastic loading and the other by multiphysics oscillations. We discuss the implications of these results for characterizing the transition from stable aseismic slip to unstable seismic slip in the context of natural and induced seismicity.&lt;/p&gt;

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