Complex Earthquake Sequences On Simple Faults

Cattania, Camilla

doi:10.1029/2019gl083628

Cited by 73 publications

(111 citation statements)

References 50 publications

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“…Furthermore, we see a downward shift in earthquake hypocenter locations, which is also an expected phenomenon for mode III earthquake cycles due to the loading conditions (Lapusta & Rice, 2003). Another effect is the increase in recurrence intervals of the large earthquakes, which can be attributed to a reduced shear modulus in the medium (Cattania, 2019). Despite these differences, we do not observe complexities such as variations in hypocenter locations or earthquake sizes as observed in fault zone simulations.…”

Section: Effects Of Reduced Nucleation Sizes In Homogeneous Mediumsupporting

confidence: 58%

Effect of fault damage zones on long-term earthquake behavior on mature strike-slip faults

Thakur¹,

Huang²,

Kaneko³

2020

Preprint

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Mature strike-slip faults are usually surrounded by a narrow zone of damaged rocks characterized by low seismic wave velocities. Observations of earthquakes along such faults indicate that seismicity is highly concentrated within this fault damage zone. However, the long-term influence of the fault damage zone on complete earthquake cycles, i.e., years to centuries, is not well understood. We simulate aseismic slip and dynamic earthquake rupture on a vertical strike-slip fault surrounded by a fault damage zone for a thousand-year timescale using observations along major strike-slip faults, e.g., San Andreas Fault, as constraints on fault zone material properties and geometry. We find that dynamic wave reflections, whose characteristics are strongly dependent on the width and the rigidity contrast of the fault damage zone, have a prominent effect on the stressing history of the fault. The presence of elastic damage can explain, in part, the variability in the earthquake sizes and hypocenter locations along a single fault, which vary with fault damage zone depth, width and rigidity contrast from the host rock. The depth extent of the fault damage zone has a pronounced effect on the earthquake hypocenter locations, and shallower fault damage zones favor shallower hypocenters with a possible bimodal distribution of seismicity along depth. Our findings also suggest significant fault damage zone effects on the hypocenter distribution when the fault damage zone penetrates to the nucleation sites of earthquakes. Therefore the depth distribution of seismicity in mature strike-slip faults is likely influenced by both lithological (material) and rheological (frictional) boundaries.

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Section: Effects Of Reduced Nucleation Sizes In Homogeneous Mediumsupporting

confidence: 58%

Effect of fault damage zones on long-term earthquake behavior on mature strike-slip faults

Thakur¹,

Huang²,

Kaneko³

2020

Preprint

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“…3c), where small events (L < L vw ) partially break the seismogenic zone from the edges. Small, non-characteristic events are known to emerge in rate-and-state friction models in homogeneous media and large seismogenic zones (L vw >> L nuc ) (Cattania, 2019;Barbot, 2019). The LVFZ thickness and damage values promoting variable event magnitudes in our models are well understood by the increase in the L vw /L nuc ratio due to the reduction in L nuc induced by the LVFZ (Fig.…”

Section: Resultsmentioning

confidence: 70%

Fault-zone damage promotes pulse-like rupture and back-propagating fronts via quasi-static effects

Idini¹,

Ampuero²

2022

Preprint

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Damage zones are ubiquitous components of faults that may affect the nucleation, propagation and arrest of earthquake ruptures. Dynamic rupture simulations show that waves trapped in a fault damage zone can induce pulse-like rupture, a mode of earthquake rupture propagation that is a primary candidate for the origin of fault slip complexity and for the apparent weakness of major faults. However, the efficiency of the mechanism revealed in previous studies depends strongly on arbitrarily prescribed initial stresses. Here, we investigate the promotion of pulse-like rupture by damaged fault zones through numerical simulations of multiple earthquake cycles in which the distribution of initial stress before each rupture is a self-consistent result of the earthquake cycle. We consider a fault bisecting a homogeneous low-rigidity layer embedded in an intact medium. Using scaling arguments we show that pulse-like ruptures are expected to appear in a highly compliant fault zone after the rupture has grown larger than the fault zone thickness. We confirm this result by conducting quasi-dynamic earthquake cycle simulations on fault zones with varying degrees of damage and thickness. Over a wide range of fault zone properties, fault-zone effects produce pulse-like ruptures with shorter rise-times and flatter slip profiles than ruptures in an intact homogeneous medium. We also find complex rupture patterns involving back-propagating secondary fronts that emerge from the primary rupture front and propagate in the opposite direction. These complex slip patterns robustly persist over multiple earthquake cycles. While such patterns are challenging to resolve in current seismological observations of large earthquakes, slow-slip numerical models show similar slip complexity, suggesting a connection between a basic structural feature of faults and rapid-tremor-reversals observed during episodic tremor and slip in Cascadia and Japan.

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“…As derived in the supporting information from Cattania (2019), the number of earthquakes per mainshock cycle increases from N ( m > m min )/ N c to N ′ ( m > m min )/ N c ( N c being the number of mainshock cycles) as the square root of σ , so that

normallog \frac{N' false(m > m_{m i n} false)}{N false(m > m_{m i n} false)} = \frac{1}{2} normallog \frac{σ}{σ_{0}} .

…”

Section: Resultsmentioning

confidence: 99%

Stress‐Dependent b Value Variations in a Heterogeneous Rate‐and‐State Fault Model

Dublanchet

2020

Geophysical Research Letters

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The magnitudes of earthquakes are known to follow a power law distribution referred to as the Gutenberg‐Richter empirical law. Seismological observations and laboratory experiments suggest a decrease of the decay exponent (b value) with differential stress. The physical mechanism controlling this decrease, however, remains unclear. The present study is dedicated to the origin of relative b value variations with stress obtained in a 2‐D rate‐and‐state planar fault model considering a population of asperities with size‐dependent fracture energy. The simulations show that both b value in the intermediate magnitude range and mainshock magnitude increase with normal stress. Analytical relationships are derived, showing that the increase of b value is related to the decrease of critical nucleation length with normal stress, enhancing the productivity of small‐magnitude events and partial ruptures. The theoretical formulas also show how the increase of mainshock magnitude is a consequence of normal stress dependence of stress drop.

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Complex Earthquake Sequences On Simple Faults

Cited by 73 publications

References 50 publications

Effect of fault damage zones on long-term earthquake behavior on mature strike-slip faults

Effect of fault damage zones on long-term earthquake behavior on mature strike-slip faults

Fault-zone damage promotes pulse-like rupture and back-propagating fronts via quasi-static effects

Stress‐Dependent b Value Variations in a Heterogeneous Rate‐and‐State Fault Model

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