Preliminary results on the characterisation of the Guaycume fault (El Salvador) from geodetic and seismological data

The Guaycume fault is a right-lateral strike-slip structure located in Western El Salvador, within the El Salvador Fault Zone (ESFZ). The ESFZ consists of a strike-slip fault system extending through the Central American Volcanic Arc, on the western margin of the Chort&#237;s block, where the Cocos plate subducts under the Caribbean plate.The Guaycume fault has been proposed as a possible source for the Mw 6.4 1917 El Salvador destructive earthquake, presenting high seismic potential in close proximity to San Salvador (Alonso-Henar et al., 2018). Its geomorphological expression has been clearly identified (Martinez-Diaz et al., 2016); however, few specific studies are currently published, and its behaviour and kinematics remain widely unknown. Notably, there is a lack of precise information about the amount of deformation that this fault currently absorbs of the westward movement (relative to the Chort&#237;s block) of the forearc sliver.We process GNSS data in the area from 2007 to 2020 in order to retrieve the GNSS velocity field surrounding the Guaycume fault. We use these data to perform a thorough kinematic study, updating the previously existing slip rates (Staller et al., 2016). Combined with seismological data, this information allows us to understand the seismic cycle of the fault to a better extent, thus leading to a better comprehension of its seismic potential.

Download Full-text

TOWARDS A PRECISE MODELLING OF THE EL SALVADOR FAULT ZONE USING GEODETIC TECHNIQUES

10.4995/cigeo2021.2021.12711 ◽

2021 ◽

Author(s):

Juan J. Portela-Fernandez ◽

Alejandra Staller ◽

Marta Bejar-Pizarro

Keyword(s):

El Salvador ◽

Fault Zone ◽

Surface Deformation ◽

Seismic Hazard Assessment ◽

Tectonic Activity ◽

Cocos Plate ◽

Slip Rates ◽

Seismic Potential ◽

Measuring Surface ◽

The Individual

The El Salvador Fault Zone (ESFZ) comprises a set of a strike-slip faults, extending through the Central American VolcanicArc within El Salvador, where the Cocos plate subducts under the Caribbean plate. These structures act as a boundarybetween the forearc sliver and the western margin of the Chortís block, accommodating the relative movement betweenthem. The ESFZ has been responsible for several shallow, destructive earthquakes in El Salvador, thus posing a seriousthreat for millions of inhabitants. Understanding its seismic potential and the behaviour of its different segments results ofgreat importance for the assessment and mitigation of seismic risk in the region. Geodetic techniques, such as GNSS andInSAR, are useful tools for measuring surface deformation related to tectonic activity. We are in the process of updatingand densifying the existing GNSS velocity field in El Salvador, aiming to characterise the individual faults in the region bydetermining their slip rates and locking depth. Additionally, we will process InSAR data, trying to obtain a continuousmeasurement of the interseismic deformation. The combination of this information with other data (e.g. seismological andgeological) through kinematic models will allow us to better understand the factors controlling the seismogenic behaviourof the ESFZ faults, evaluate their seismic potential and improve the seismic hazard assessment.

Download Full-text

Geodynamic and seismotectonic model of a long-lived transverse structure: The Schio-Vicenza Fault System (NE Italy)

Solid Earth ◽

10.5194/se-12-1967-2021 ◽

2021 ◽

Vol 12 (8) ◽

pp. 1967-1986

Author(s):

Dario Zampieri ◽

Paola Vannoli ◽

Pierfrancesco Burrato

Keyword(s):

Active Faults ◽

Strike Slip ◽

Southern Alps ◽

Fault System ◽

Thrust Belt ◽

Geological Evidence ◽

Slip Activity ◽

Seismological Data ◽

Moderate Seismicity ◽

Northern Segment

Abstract. We make a thorough review of geological and seismological data on the long-lived Schio-Vicenza Fault System (SVFS) in northern Italy and present for it a geodynamic and seismotectonic interpretation. The SVFS is a major and high-angle structure transverse to the mean trend of the eastern Southern Alps fold-and-thrust belt, and the knowledge of this structure is deeply rooted in the geological literature and spans more than a century and a half. The main fault of the SVFS is the Schio-Vicenza Fault (SVF), which has a significant imprint in the landscape across the eastern Southern Alps and the Veneto-Friuli foreland. The SVF can be divided into a northern segment, extending into the chain north of Schio and mapped up to the Adige Valley, and a southern one, coinciding with the SVF proper. The latter segment borders to the east the Lessini Mountains, Berici Mountains and Euganei Hills block, separating this foreland structural high from the Veneto-Friuli foreland, and continues southeastward beneath the recent sediments of the plain via the blind Conselve–Pomposa fault. The structures forming the SVFS have been active with different tectonic phases and different styles of faulting at least since the Mesozoic, with a long-term dip-slip component of faulting well defined and, on the contrary, the horizontal component of the movement not being well constrained. The SVFS interrupts the continuity of the eastern Southern Alps thrust fronts in the Veneto sector, suggesting that it played a passive role in controlling the geometry of the active thrust belt and possibly the current distribution of seismic release. As a whole, apart from moderate seismicity along the northern segment and few geological observations along the southern one, there is little evidence to constrain the recent activity of the SVFS. In this context, the SVFS, and specifically its SVF strand, has accommodated a different amount of shortening of adjacent domains of the Adriatic (Dolomites) indenter by internal deformation produced by lateral variation in strength, related to Permian–Mesozoic tectonic structures and paleogeographic domains. The review of the historical and instrumental seismicity along the SVFS shows that it does not appear to have generated large earthquakes during the last few hundred years. The moderate seismicity points to a dextral strike-slip activity, which is also corroborated by the field analysis of antithetic Riedel structures of the fault cropping out along the northern segment. Conversely, the southern segment shows geological evidence of sinistral strike-slip activity. The apparently conflicting geological and seismological data can be reconciled considering the faulting style of the southern segment as driven by the indentation of the Adriatic plate, while the opposite style along the northern segment can be explained in a sinistral opening “zipper” model, where intersecting pairs of simultaneously active faults with a different sense of shear merge into a single fault system.

Download Full-text

Slip rates and seismic potential on the East Anatolian Fault System using an improved GPS velocity field

Journal of Geodynamics ◽

10.1016/j.jog.2016.01.001 ◽

2016 ◽

Vol 94-95 ◽

pp. 1-12 ◽

Cited By ~ 16

Author(s):

B. Aktug ◽

H. Ozener ◽

A. Dogru ◽

A. Sabuncu ◽

B. Turgut ◽

...

Keyword(s):

Velocity Field ◽

Fault System ◽

Slip Rates ◽

Seismic Potential ◽

Gps Velocity Field ◽

East Anatolian Fault

Download Full-text

Late Quaternary slip rates for faults of the central Walker Lane (Nevada, USA): Spatiotemporal strain release in a strike-slip fault system

Geosphere ◽

10.1130/ges02088.1 ◽

2019 ◽

Vol 15 (5) ◽

pp. 1460-1478 ◽

Cited By ~ 5

Author(s):

Stephen J. Angster ◽

Steven G. Wesnousky ◽

Paula M. Figueiredo ◽

Lewis A. Owen ◽

Sarah J. Hammer

Keyword(s):

Late Pleistocene ◽

Strike Slip ◽

Strike Slip Fault ◽

Luminescence Dating ◽

Slip Distribution ◽

Fault System ◽

Slip Rates ◽

Walker Lane ◽

Fault Systems ◽

Late Pleistocene To Holocene

Abstract The Walker Lane is a broad shear zone that accommodates a significant portion of North American–Pacific plate relative transform motion through a complex of fault systems and block rotations. Analysis of digital elevation models, constructed from both lidar data and structure-from-motion modeling of unmanned aerial vehicle photography, in conjunction with 10Be and 36Cl cosmogenic and optically stimulated luminescence dating define new Late Pleistocene to Holocene minimum strike-slip rates for the Benton Springs (1.5 ± 0.2 mm/yr), Petrified Springs (0.7 ± 0.1 mm/yr), Gumdrop Hills (0.9 +0.3/−0.2 mm/yr), and Indian Head (0.8 ± 0.1 mm/yr) faults of the central Walker Lane (Nevada, USA). Regional mapping of the fault traces within Quaternary deposits further show that the Indian Head and southern Benton Springs faults have had multiple Holocene ruptures, with inferred coseismic displacements of ∼3 m, while absence of displaced Holocene deposits along the Agai Pah, Gumdrop Hills, northern Benton Springs, and Petrified Springs faults suggest they have not. Combining these observations and comparing them with geodetic estimates of deformation across the central Walker Lane, indicates that at least one-third of the ∼8 mm/yr geodetic deformation budget has been focused across strike-slip faults, accommodated by only two of the five faults discussed here, during the Holocene, and possibly half from all the strike-slip faults during the Late Pleistocene. These results indicate secular variations of slip distribution and irregular recurrence intervals amongst the system of strike-slip faults. This makes the geodetic assessment of fault slip rates and return times of earthquakes on closely spaced strike-slip fault systems challenging. Moreover, it highlights the importance of understanding temporal variations of slip distribution within fault systems when comparing geologic and geodetic rates. Finally, the study provides examples of the importance and value in using observations of soil development in assessing the veracity of surface exposure ages determined with terrestrial cosmogenic nuclide analysis.

Download Full-text

High-Resolution 3D Seismic Imaging of Fault Interaction and Deformation Offshore San Onofre, California

Frontiers in Earth Science ◽

10.3389/feart.2021.653672 ◽

2021 ◽

Vol 9 ◽

Author(s):

James J. Holmes ◽

Neal W. Driscoll ◽

Graham M. Kent

Keyword(s):

High Resolution ◽

Strike Slip ◽

Fault System ◽

3D Seismic ◽

Fault Interaction ◽

Slip Rates ◽

Slip Step ◽

Well Data ◽

Splay Faults ◽

Step Over

The Inner California Borderland (ICB) records a middle Oligocene transition from subduction to microplate capture along the southern California and Baja coast. The closest nearshore fault system, the Newport-Inglewood/Rose Canyon (NIRC) fault complex is a dextral strike-slip system that extends primarily offshore approximately 120 km from San Diego to Newport Beach, California. Holocene slip rates along the NIRC are 1.5–2.0 mm/year in the south and 0.5 mm/year along its northern extent based on trenching and well data. High-resolution 3D seismic surveys of the NIRC fault system offshore of San Onofre were acquired to define fault interaction across a prominent strike-slip step-over. The step-over deformation results in transpression that structurally controls the width of the continental shelf in this region. Shallow coring on the shelf yields a range of sedimentation rates from 0.27–0.28 mm/year. Additionally, a series of smaller anticlines and synclines record subtle changes in fault trends along with small step-overs and secondary splay faults. Finally, sedimentary units onlapping and dammed by the anticline, place constraints on the onset of deformation of this section of the NIRC fault system. Thickness estimates and radiocarbon dating yield ages of 560,000 to 575,000 years before present for the onset of deformation.

Download Full-text

Geometric and Dynamic Patterns of the Golmud Segment in the Southern Marginal Fault of the Qaidam Basin

Frontiers in Earth Science ◽

10.3389/feart.2021.636554 ◽

2021 ◽

Vol 9 ◽

Author(s):

Hao Luo ◽

Ji Wang ◽

Yasen Gou ◽

Hongmei Yu ◽

Peng Shu ◽

...

Keyword(s):

High Resolution ◽

Late Quaternary ◽

Qaidam Basin ◽

Structural Evolution ◽

Strike Slip ◽

Fault System ◽

Tibet Plateau ◽

Deformation Pattern ◽

Slip Rates ◽

Lateral Extrusion

The southern marginal fault of the Qaidam Basin (SMQBF) is a block-bounding border fault that has played a key role in the structural evolution of the Kunlun Fault. However, its geometric and dynamic deformation patterns since the Late Pleistocene have not been clearly observed. Field investigations, combined with high-resolution imagery and shallow seismic profiles, show that the SMQBF is a thrust fault with a sinistral strike-slip component composed of several secondary faults. Its Late Quaternary deformation pattern is characterized by piggyback thrust propagation, and the frontal fault may not be exposed to the surface. Due to the flexural slip of the hanging strata of the secondary fault, sub-parallel faults with widths of thousands of meters have formed on high terraces; these are important when assessing the seismic hazard of this area. Based on high-resolution topographic data obtained using an unmanned erial vehicle and optically stimulated luminescence chronology, the slip rates of several secondary faults were obtained. The vertical and strike-slip rates of the SMQBF were determined to be 0.96 ± 0.33 mm/a and 2.66 ± 0.50 mm/a, respectively, which may be the minimum rates for the fault. Considering that the SMQBF is composed of several secondary faults, these rates possibly correspond to minimum deformation only. The evident sinistral strike-slip of the SMQBF indicates that although the sinistral slip of the Kunlun Fault system is concentrated in main fault of this system, the branch faults have a significant influence on the lateral extrusion of the Qinghai-Tibet Plateau.

Download Full-text