Effects of source model variations on Coulomb stress analyses of a multi-fault intraplate earthquake sequence

Mohammadi, Hiwa; Quigley, Mark; Steacy, S.; Duffy, Brendan

doi:10.1016/j.tecto.2019.06.007

Cited by 13 publications

(14 citation statements)

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“…The Tennant Creek event comprises three mainshocks in a 12-hr period on the 22 January 1988, with three separate scarps recognized at the surface. Analysis of available seismological and surface data supports a direct association between each mainshock and an individual rupture (TC1: Kunayungku; TC2: Lake Surprise west; TC3: Lake Surprise east) [57,59,62,69] and they are treated as separate events in this paper.…”

Section: Review Data Methods and Terminologysupporting

confidence: 56%

Surface-Rupturing Historical Earthquakes in Australia and Their Environmental Effects: New Insights from Re-Analyses of Observational Data

2019

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We digitize surface rupture maps and compile observational data from 67 publications on ten of eleven historical, surface-rupturing earthquakes in Australia in order to analyze the prevailing characteristics of surface ruptures and other environmental effects in this crystalline basement-dominated intraplate environment. The studied earthquakes occurred between 1968 and 2018, and range in moment magnitude (Mw) from 4.7 to 6.6. All earthquakes involved co-seismic reverse faulting (with varying amounts of strike-slip) on single or multiple (1–6) discrete faults of ≥ 1 km length that are distinguished by orientation and kinematic criteria. Nine of ten earthquakes have surface-rupturing fault orientations that align with prevailing linear anomalies in geophysical (gravity and magnetic) data and bedrock structure (foliations and/or quartz veins and/or intrusive boundaries and/or pre-existing faults), indicating strong control of inherited crustal structure on contemporary faulting. Rupture kinematics are consistent with horizontal shortening driven by regional trajectories of horizontal compressive stress. The lack of precision in seismological data prohibits the assessment of whether surface ruptures project to hypocentral locations via contiguous, planar principal slip zones or whether rupture segmentation occurs between seismogenic depths and the surface. Rupture centroids of 1–4 km in depth indicate predominantly shallow seismic moment release. No studied earthquakes have unambiguous geological evidence for preceding surface-rupturing earthquakes on the same faults and five earthquakes contain evidence of absence of preceding ruptures since the late Pleistocene, collectively highlighting the challenge of using mapped active faults to predict future seismic hazards. Estimated maximum fault slip rates are 0.2–9.1 m Myr-1 with at least one order of uncertainty. New estimates for rupture length, fault dip, and coseismic net slip can be used to improve future iterations of earthquake magnitude—source size—displacement scaling equations. Observed environmental effects include primary surface rupture, secondary fracture/cracks, fissures, rock falls, ground-water anomalies, vegetation damage, sand-blows / liquefaction, displaced rock fragments, and holes from collapsible soil failure, at maximum estimated epicentral distances ranging from 0 to ~250 km. ESI-07 intensity-scale estimates range by ± 3 classes in each earthquake, depending on the effect considered. Comparing Mw-ESI relationships across geologically diverse environments is a fruitful avenue for future research.

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Section: Review Data Methods and Terminologysupporting

confidence: 56%

Surface-Rupturing Historical Earthquakes in Australia and Their Environmental Effects: New Insights from Re-Analyses of Observational Data

2019

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“…We attribute this difference to the depth of the earthquake source. Our rupture width estimates for the Kunayungku and Lake Surprise East earthquakes range from 9.8 -11.6 km (Table S5), while published estimates extend from the surface to depths of > 6 km (Choy and Bowman, 1990) and up to 10 -16 km (Bowman, 1991;Mohammadi et al, 2019).…”

Section: Scaling Between MD Srl and Mwmentioning

confidence: 83%

“…1C), where multiple mainshocks and surface ruptures were previously amalgamated into a single event (Wells and Coppersmith, 1994;Wesnousky, 2008) despite the earthquakes occurring several hours apart within a 12-hour period and producing independent scarps (Bowman, 1992). Therefore, we treat them as three separate events of Mw = 6.2 (Kunayungku), 6.3 (Lake Surprise West) and 6.5 (Lake Surprise East) with their own surface rupture traces (Mohammadi et al, 2019). Three of those Mw > 5.7…”

Section: Co-seismic Slip Distributions and Rupture Segmentationmentioning

confidence: 99%

“…Together with the paucity of preceding, historical Mw > 6 events on these fault systems (Leonard, 2008;Leonard et al, 2014), this suggests variations in slip rate, interseismic creep, local-to-regional stress perturbations relating to prior earthquake(s), and fault structural maturity (i.e., the roughness of the fault plane, which is physically scaled to D -0.1 where D is the cumulative displacement of a fault (Brodsky et al, 2011)) may be of minimal significance to interpreting any slip distribution variability observed in these earthquakes. With the exception of the three surface-rupturing earthquakes on neighboring faults in the 1988 Tennant Creek sequence, which have been explained by proximate Coulomb stress transfer (Mohammadi et al, 2019), 8 of the 11 Australian ruptures are thus considered to be spatially and temporally isolated, with slip distributions that are unlikely to have been strongly influenced by preceding, spatiotemporally proximate earthquakes.…”

Section: Introductionmentioning

confidence: 99%

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Surface slip distributions and geometric complexity of intraplate reverse-faulting earthquakes

Yang¹,

Quigley²,

King³

2022

Preprint

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Earthquake ground surface ruptures provide insights into faulting mechanics and inform seismic hazard analyses. Surface ruptures for eleven historical (1968 to 2018) moment magnitude (Mw) 4.7 to 6.6 reverse earthquakes in Australia are analyzed using statistical techniques and compared to magnetic, gravity, and stress trajectory datasets. Of the total combined (summative) length of all surface ruptures (~148 km), 133 km (90%) to 145 km (98%) align with geophysical structure in the host basement rocks. Surface rupture length (SRL), maximum displacement (MD), and probability of surface rupture at a specified Mw are high compared with equivalent Mw earthquakes globally. This is attributed to (i) steep cratonic crustal strength gradient at shallow depths promoting shallow hypocenters (~1 to 6 km) and limiting down-dip rupture widths (~1 to 8.5 km), and (ii) favorably-aligned crustal anisotropies (e.g., bedrock foliations , faults, fault intersections) that enhance lateral rupture propagation and/or surface displacements. Combined (modeled and observed) MDs are in the middle third of the SRL with 68% probability, and either the ≤ 33rd and ≥ 66th percentiles of SRL with 16% probability. MD occurs proximate to or directly within zones of enhanced fault geometric complexity (as evidenced from surface ruptures) in 8 of 11 earthquakes (73%). MD can be approximated by 3.3 ± 1.6 (1σ) × AD (average displacement). S-transform analysis indicates high-frequency slip maxima also coincide with fault geometric complexities, consistent with stress amplifications and enhanced slip variability due to geometric and kinematic interactions with neighboring faults. Rupture slip taper angles exhibit large variations (-90 % to + 380 % with respect to the mean value) towards rupture termini and are steepest where ruptures terminate at obliquely-oriented magnetic lineaments and/or lithology changes. Incremental slip approximates AD between the 10th and 90th percentiles of the SRL. The average static stress drop of the studied earthquakes is 4.8 ± 2.8 MPa. A surface rupture classification scheme in cratonic stable regions is provided to describe the prevailing characteristics of intraplate earthquakes across diverse crustal structural-geophysical settings. New scaling relationships and suggestions for logic tree weights are provided to enhance probabilistic fault displacement hazard analyses for bedrock-dominated intraplate continental regions.

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“…Although it is well known that faults are nonplanar (e.g., Candela et al, 2011; Nicholson, Plesch, & Shaw, 2017; Plesch et al, 2007), studies that model static Coulomb stress transfer have routinely employed simplified planar fault geometries (e.g., Harris & Simpson, 1992; Lin & Stein, 2004; Mohammadi et al, 2019; Pace et al, 2014). Recent work has attempted to address this issue, and studies indicate that fault geometry exerts a strong control on the magnitude of stress transfer between faults by altering patterns of local stress distribution (Biasi & Wesnousky, 2016; Bie & Ryder, 2014; Madden et al, 2013; Marshall & Morris, 2012; Mildon et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Three‐Dimensional Structure, Ground Rupture Hazards, and Static Stress Models for Complex Nonplanar Thrust Faults in the Ventura Basin, Southern California

et al. 2020

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To investigate the subsurface geometry of a recently discovered, seismically active fault in the Ventura basin, southern California, USA, we present a series of cross sections and a new three-dimensional fault model across the Southern San Cayetano fault (SSCF) based on integration of surface data with petroleum industry well log data. Additionally, the fault model for the SSCF, along with models of other regional faults extracted from the Southern California Earthquake Center three-dimensional Community Fault Model, are incorporated in static Coulomb stress modeling to investigate static Coulomb stress transfer between thrust faults with complex geometry and to further our understanding of stress transfer in the Ventura basin. The results of the subsurface well investigation provide evidence for a low-angle SSCF that dips~15°north and connects with the western section of the San Cayetano fault around 1.5-3.5 km depth. We interpret the results of static Coulomb stress models to partly explain contrasting geomorphic expression between different sections of the San Cayetano fault and a potential mismatch in timings between large-magnitude uplift events suggested by paleoseismic studies on the Pitas Point, Ventura, and San Cayetano faults. In addition to new insights into the structure and potential rupture hazard of a recently discovered active reverse fault in a highly populated area of southern California, this study provides a simple method to model static Coulomb stress transfer on complex geometry faults in fold and thrust belts.

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Effects of source model variations on Coulomb stress analyses of a multi-fault intraplate earthquake sequence

Cited by 13 publications

References 75 publications

Surface-Rupturing Historical Earthquakes in Australia and Their Environmental Effects: New Insights from Re-Analyses of Observational Data

Surface-Rupturing Historical Earthquakes in Australia and Their Environmental Effects: New Insights from Re-Analyses of Observational Data

Surface slip distributions and geometric complexity of intraplate reverse-faulting earthquakes

Three‐Dimensional Structure, Ground Rupture Hazards, and Static Stress Models for Complex Nonplanar Thrust Faults in the Ventura Basin, Southern California

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