Magnitude, timing, and rate of slip along the Atacama fault system, northern Chile: Implications for Early Cretaceous slip partitioning and plate convergence

2021 ◽  
pp. jgs2020-142
Author(s):  
N.M. Seymour ◽  
J.S. Singleton ◽  
R. Gomila ◽  
S.P. Mavor ◽  
G. Heuser ◽  
...  
Keyword(s):  
Convergence Rates ◽  
Slip Rate ◽  
Structural Data ◽  
Fault System ◽  
Content Type ◽  
Plate Convergence ◽  
Oblique Convergence ◽  
Slip History ◽  
Supplementary Material ◽  
Atacama Fault System

Displacement estimates along the Atacama fault system (AFS), a crustal-scale sinistral structure that accommodated oblique convergence in the Mesozoic Coastal Cordillera arc, vary widely due to a lack of piercing points. We mapped the distribution of plutons and mylonitic deformation along the northern ∼70 km of the El Salado segment and use U-Pb geochronology to establish the slip history of the AFS. Along the eastern branch, mylonitic fabrics associated with the synkinematic ∼134–132 Ma Cerro del Pingo Complex are separated by 34–38 km, and mylonites associated with a synkinematic ∼120–119 Ma tonalite are separated by 20.5–25 km. We interpret leucocratic intrusions to be separated across the western branch by ∼16–20 km, giving a total slip magnitude of ∼54 ± 6 km across the El Salado segment. Kinematic indicators consistently record sinistral shear and zircon (U-Th)/He data suggest dip-slip motion was insignificant. Displacement occurred between ∼133–110 Ma at a slip rate of ∼2.1–2.6 km/Myr. This slip rate is low compared to modern intra-arc strike-slip faults, suggesting (1) the majority of lateral slip was accommodated along the slab interface or distributed through the forearc or (2) plate convergence rates/obliquity were significantly lower than previously modeled.Supplementary material including full U-Pb, (U-Th)/He, petrographic, and structural data with locations is available at https://doi.org/10.6084/m9.figshare.c.5262177.

scholarly journals Outcrop-scale manifestations of reactivation during multiple superimposed rifting and basin inversion events: the Devonian Orcadian Basin, northern Scotland

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-089 ◽  
Author(s):  
A.M. Dichiarante ◽  
R.E. Holdsworth ◽  
E.D. Dempsey ◽  
K.J.W. McCaffrey ◽  
T.A.G. Utley
Keyword(s):  
Structural Complexity ◽  
Structural Data ◽  
Dominant Group ◽  
Content Type ◽  
Basin Inversion ◽  
Supplementary Material ◽  
Group 2 ◽  
Orcadian Basin ◽  
East West ◽  
Group 1

The Devonian Orcadian Basin in Scotland hosts extensional fault systems assumed to be related to the initial formation of the basin, with only limited post-Devonian inversion and reactivation. However, a recent detailed structural study across Caithness, underpinned by published Re–Os geochronology, shows that three phases of deformation are present. North–south- and NW–SE-trending Group 1 faults are related to Devonian ENE–WSW transtension associated with sinistral shear along the Great Glen Fault during the formation of the Orcadian Basin. Metre- to kilometre-scale north–south-trending Group 2 folds and thrusts are developed close to earlier sub-basin-bounding faults and reflect late Carboniferous–early Permian east–west inversion associated with dextral reactivation of the Great Glen Fault. The dominant Group 3 structures are dextral oblique NE–SW-trending and sinistral east–west-trending faults with widespread syndeformational carbonate mineralization (± pyrite and bitumen) and are dated using Re–Os geochronology as Permian (c. 267 Ma). Regional Permian NW–SE extension related to the development of the offshore West Orkney Basin was superimposed over pre-existing fault networks, leading to local oblique reactivation of Group 1 faults in complex localized zones of transtensional folding, faulting and inversion. The structural complexity in surface outcrops onshore therefore reflects both the local reactivation of pre-existing faults and the superimposition of obliquely oriented rifting episodes during basin development in the adjacent offshore areas.Supplementary material: Stereographic projections of compiled structural data from individual fieldwork localities are available at https://doi.org/10.6084/m9.figshare.c.5115228

scholarly journals Active faults sources for the Pátzcuaro–Acambay fault system (Mexico): fractal analysis of slip rates and magnitudes <i>M</i><sub>w</sub> estimated from fault length

2018 ◽  
Vol 18 (11) ◽  
pp. 3121-3135
Author(s):  
Avith Mendoza-Ponce ◽  
Angel Figueroa-Soto ◽  
Diana Soria-Caballero ◽  
Víctor Hugo Garduño-Monroy
Keyword(s):  
Time Domain ◽  
Fractal Analysis ◽  
Active Faults ◽  
Slip Rate ◽  
Spatial Domain ◽  
Fault System ◽  
Slip Rates ◽  
Oblique Convergence ◽  
Definition Of ◽  
Intrinsic Definition

Abstract. The Pátzcuaro–Acambay fault system (PAFS), located in the central part of the Trans-Mexican Volcanic Belt (TMVB), is delimited by an active transtensive deformation area associated with the oblique subduction zone between the Cocos and North American plates, with a convergence speed of 55 mm yr−1 at the latitude of the state of Michoacán, Mexico. Part of the oblique convergence is transferred to this fault system, where the slip rates range from 0.009 to 2.78 mm yr−1. This has caused historic earthquakes in Central Mexico, such as the Acambay quake (Ms=6.9) on 19 November 1912 with surface rupture, and another in Maravatío in 1979 with Ms=5.6. Also, paleoseismic analyses are showing Quaternary movements in some faults, with moderate to large magnitudes. Notably, this zone is seismically active, but lacks a dense local seismic network, and more importantly, its neotectonic movements have received very little attention. The present research encompasses three investigations carried out in the PAFS. First, the estimation of the maximum possible earthquake magnitudes, based on 316 fault lengths mapped on a 15 m digital elevation model, by means of three empirical relationships. In addition, the Hurst exponent Hw and its persistence, estimated for magnitudes Mw (spatial domain) and for 32 slip-rate data (time domain) by the wavelet variance analysis. Finally, the validity of the intrinsic definition of active fault proposed here. The average results for the estimation of the maximum and minimum magnitudes expected for this fault population are 5.5≤Mw≤7. Also, supported by the results of H at the spatial domain, this paper strongly suggests that the PAFS is classified in three different zones (western PAFS, central PAFS, and eastern PAFS) in terms of their roughness (Hw=0.7,Hw=0.5,Hw=0.8 respectively), showing different dynamics in seismotectonic activity and; the time domain, with a strong persistence Hw=0.949, suggests that the periodicities of slip rates are close in time (process with memory). The fractal capacity dimension (Db) is also estimated for the slip-rate series using the box-counting method. Inverse correlation between Db and low slip-rate concentration was observed. The resulting Db=1.86 is related to a lesser concentration of low slip-rates in the PAFS, suggesting that larger faults accommodate the strain more efficiently (length ≥3 km). Thus, in terms of fractal analysis, we can conclude that these 316 faults are seismically active, because they fulfill the intrinsic definition of active faults for the PAFS.

scholarly journals Fast Holocene slip and localized strain along the Liquiñe-Ofqui strike-slip fault system, Chile

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Luis Astudillo-Sotomayor ◽  
Julius Jara-Muñoz ◽  
Daniel Melnick ◽  
Joaquín Cortés-Aranda ◽  
Andrés Tassara ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Strain Localization ◽  
Slip Rate ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault System ◽  
Plate Convergence ◽  
Active Tectonic ◽  
Millennial Time Scale ◽  
Hazard Assessments

AbstractIn active tectonic settings dominated by strike-slip kinematics, slip partitioning across subparallel faults is a common feature; therefore, assessing the degree of partitioning and strain localization is paramount for seismic hazard assessments. Here, we estimate a slip rate of 18.8 ± 2.0 mm/year over the past 9.0 ± 0.1 ka for a single strand of the Liquiñe-Ofqui Fault System, which straddles the Main Cordillera in Southern Chile. This Holocene rate accounts for ~ 82% of the trench-parallel component of oblique plate convergence and is similar to million-year estimates integrated over the entire fault system. Our results imply that strain localizes on a single fault at millennial time scale but over longer time scales strain localization is not sustained. The fast millennial slip rate in the absence of historical Mw > 6.5 earthquakes along the Liquiñe-Ofqui Fault System implies either a component of aseismic slip or Mw ~ 7 earthquakes involving multi-trace ruptures and > 150-year repeat times. Our results have implications for the understanding of strike-slip fault system dynamics within volcanic arcs and seismic hazard assessments.

scholarly journals The active Nea Anchialos Fault System (Central Greece): comparison of geological, morphotectonic, archaeological and seismological data

1996 ◽  
Vol 39 (3) ◽  
Author(s):  
R. Caputo
Keyword(s):  
Stress Field ◽  
Late Quaternary ◽  
Slip Rate ◽  
Structural Data ◽  
Fault Slip ◽  
Fault System ◽  
Middle Pleistocene ◽  
Integrated Analysis ◽  
Archaeological Data ◽  
Seismological Data

The Nea Anchialos Fault System has been studied integrating geological, morphological, structural, archaeological and seismic data. This fault system forms the northern boundary of the Almyros Basin which is one of the Neogene-Quaternary tectonic basins of Thessaly. Specific structural and geomorphological mapping were carried out and fault-slip data analysis allowed the Late Quaternary palaeo-stress field to be estimated. The resulting N-S trending purely extensional regime is consistent with the direction of the T-axes computed from the focal mechanisms of the summer 1980, Volos seismic sequence and the April 30, 1985 Almyros earthquake. A minor set of structural data indicates a WNW-ESE extension which has been interpreted as due to a local and second order stress field occurring during the N-S regional extension. Furthermore, new archaeological data, discovered by the author, have improved morphology and tectonics of the area also allowing a tentative estimate of the historic (III-IV century AD. to Present) fault slip rate. Several topographic profiles across the major E- W topographic escarpment as well as along the streams, have emphasised scarps and knick-points, further supporting the occurrence of very recent morphogenic activity. In the last section, the structural, morphological and archaeological data are compared with the already existing seismological data and their integrated analysis indicates that the Nea Anchialos Fault System has been active since Lower(?)-Middle Pleistocene.

scholarly journals Patterns of Silurian deformation and magmatism during sinistral oblique convergence, northern Scottish Caledonides

2020 ◽  
Vol 177 (5) ◽  
pp. 893-910 ◽  
Author(s):  
R. A. Strachan ◽  
G. I. Alsop ◽  
J. Ramezani ◽  
R. E. Frazer ◽  
I. M. Burns ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Crustal Thickening ◽  
Data Sets ◽  
Content Type ◽  
Iapetus Ocean ◽  
Oblique Convergence ◽  
Synchronous Development ◽  
Thrust Zone ◽  
Supplementary Material ◽  
Structural Levels

Regional ductile thrusting and syn-kinematic granitic magmatism within the Caledonides of northern Scotland occurred within a sinistrally oblique convergent tectonic setting during the Silurian closure of the Iapetus Ocean. The highest thrust nappes are dominated by structures of probable Grampian (Ordovician) age, and Scandian (Silurian) deformation dominates the underlying thrust nappes. Deformation was overall foreland-propagating but the nappe stack was modified by out-of-sequence thrusting and probable synchronous development of thrusts at different structural levels. Localized dextrally transpressive deformation is related to an inferred lateral ramp located offshore. New U–Pb zircon ages from syn-tectonic granites indicate that the internal Naver Thrust was active between c. 432 and c. 426 Ma. This is consistent with other data sets that indicate that contractional deformation and high-grade metamorphism, and by implication displacements in the Moine Thrust Zone, may have lasted until c. 420–415 Ma. The synchroneity of thrusting and strike-slip movements along the Great Glen Fault implies that partitioning of transpressional strain occurred above a regional basal decollement. The short duration of the Scandian orogen in Scotland (c. 437–415 Ma?) is consistent with only moderate crustal thickening and a location on the periphery of the main Laurentia–Baltica collision further north.Supplementary material: Details of analytical procedures, complete U-Pb isotopic data and methods of U-Pb age calculation and error reporting are available at https://doi.org/10.6084/m9.figshare.c.4962251

STRUCTURAL EVOLUTION OF THE INTRA-ARC ATACAMA FAULT SYSTEM DURING OBLIQUE CONVERGENCE

2019 ◽  
Author(s):  
Nikki M. Seymour ◽  
◽  
John S. Singleton ◽  
Rodrigo Gomila ◽  
Gert Heuser ◽  
...  
Keyword(s):  
Structural Evolution ◽  
Fault System ◽  
Oblique Convergence ◽  
Atacama Fault System
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