Rapid Postearthquake Field Reconnaissance, Paleoseismic Trenching, and GIS-Based Fault Slip Variability Measurements along the Mw 6.4 and Mw 7.1 Ridgecrest Earthquake Sequence, Southern California

2021 ◽  
Author(s):  
Özgür Kozacı ◽  
Christopher M. Madugo ◽  
Jeffrey L. Bachhuber ◽  
Christopher S. Hitchcock ◽  
Albert R. Kottke ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Structural Complexity ◽  
Fault Slip ◽  
Fault Rupture ◽  
Field Reconnaissance ◽  
Complex Fault ◽  
Transmission Pipeline ◽  
Fault Deformation ◽  
Fault Displacement ◽  
Deformation Patterns

ABSTRACT Understanding fault rupture deformation patterns, especially in complex fault zones, has fundamental implications on seismotectonic studies and hazard mitigation for the built environment. The 2019 Mw 6.4 and Mw 7.1 Ridgecrest earthquake ruptures offer an opportunity to quantify deformation patterns and surface displacements from a complex fault rupture. Our field reconnaissance, within 18 hr of the Mw 6.4 event, documented a complex and relatively broad fault deformation zone up to a few kilometers wide in the vicinity of a gas transmission pipeline intersected by the surface rupture south of Highway 178. The subsequent Mw 7.1 event resulted in similarly distributed surface fault deformation within a broad zone that crossed a second gas transmission pipeline located south of Highway 178. On 10 July, fault-normal pipeline assessment trenches were excavated at both locations and provided evidence for late Pleistocene fault rupture on both faults expressed as upward fault truncations and paleoliquefaction features. Subsequent imagery-based rupture-mapping facilitated identification and measurement of offset features that were not identified during field mapping. Fault displacement measurements document a gradual decrease in fault slip on rupture southwestward from the Mw 6.4 epicenter within the study area. However, displacement along the primary Mw 7.1 rupture decreased more drastically southeastward toward a structural complexity at a fault stepover expressed as a horsetail splay. Fault-normal slip distributions showed that majority of the surface deformation was accommodated along discrete fault strands within the primary fault zone across both ruptures. This work expands the catalog of high-fidelity coseismic rupture information used to better understand seismotectonic processes, while contributing to refinement of fault displacement models used in support of critical infrastructure design.

Petrinja Seismogenic Source and its 2020-2021 Earthquake Sequence (central Croatia)

2021 ◽  
Author(s):  
Vanja Kastelic ◽  
Simone Atzori ◽  
Michele M. C. Carafa ◽  
Marin Marin Govorčin ◽  
Davorka Herak ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Pannonian Basin ◽  
Structural Complexity ◽  
Earthquake Sequence ◽  
Geodynamic Setting ◽  
Natural Environments ◽  
Fault Geometry ◽  
Seismogenic Fault ◽  
Seismogenic Source ◽  
Deformation Patterns

<p>The ongoing Petrinja earthquake sequence interests a structurally complex area characterized by the transition between the Dinarides and the Pannonian Basin structural units. The sequence mainshock (December 29, 2020; Mw = 6.4) struck in the vicinity of the Petrinja town and caused significant damage in the human and in the natural environments. The preliminary seismological and geodetic analyses indicated a dextral strike-slip NW-SE oriented fault as the event source. Numerous geologic surface deformation patterns have been identified in the aftermath of the main event, including collapsed sinkholes, liquefaction, different forms of landslides, and surface fractures which nature and causative process require further detailed studies.<br>The aim of our contribution is to apply a multitude of different geophysical, geodetic and geologic methodologies to decipher the Petrinja seismogenic fault geometry in the light of its ongoing earthquake sequence. We will show how the different datasets converge in delineating the fault geometry and discuss their diverging aspects and implications. Our preliminary analyses on the geometric and kinematic characteristics of the mainshock (as well as those of the foreshocks and aftershocks) point to an important structural complexity. This aspect helps us to better understand the seismotectonic framework of the Petrinja seismogenic fault and other regional seismogenic faults of similar geologic and geodynamic setting.</p>

scholarly journals InSAR Reveals Complex Surface Deformation Patterns Over an 80,000 km 2 Oil‐Producing Region in the Permian Basin

2020 ◽  
Vol 47 (21) ◽  
Author(s):  
Scott Staniewicz ◽  
Jingyi Chen ◽  
Hunjoo Lee ◽  
Jon Olson ◽  
Alexandros Savvaidis ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Complex Surface ◽  
Permian Basin ◽  
Deformation Patterns

Off-fault Deformation Associated with Strike-slip Faults

2018 ◽  
Vol 24 (4) ◽  
pp. 375-384
Author(s):  
Jeffrey A. Johnson
Keyword(s):  
Slip Surface ◽  
Strike Slip ◽  
Earthquake Magnitude ◽  
Slip Zone ◽  
Fault Rupture ◽  
Fault Deformation ◽  
Simplified Procedure ◽  
Inelastic Strains ◽  
Adequate Design ◽  
Cultural Features

Abstract Habitable buildings can be protected from surface fault rupture by establishing structure “setback zones” similar in purpose to legally mandated zones in California and Utah. But post-earthquake surveys of offset and warped linear cultural features, believed to have been straight prior to the event, demonstrate that potentially damaging inelastic strains or off-fault deformation can extend tens of meters beyond the principal slip zone of strike-slip surface fault ruptures. Setback zones designed to also mitigate off-fault deformation are likely to be prohibitively wide, indicating the need for structural and geotechnical engineering solutions to accommodate the potentially damaging strains within adequate design buffers. This study analyzes nine strike-slip surface fault ruptures between 1906 and 2014 and develops a simplified procedure to quantify off-fault deformation based on earthquake magnitude and distance from the principal slip zone of strike-slip faults.

Changes in the location of the nucleation point of slip events on ancient normal faults

2020 ◽  
Author(s):  
Efstratios Delogkos ◽  
Conrad Childs ◽  
Tom Manzocchi ◽  
John Walsh
Keyword(s):  
Continuous Mapping ◽  
Fault Slip ◽  
Propagation Direction ◽  
Normal Faults ◽  
Northern Greece ◽  
Slip Surfaces ◽  
Local Propagation ◽  
Lignite Mine ◽  
Fault Trace ◽  
Fault Displacement

<p>The lack of an unambiguous method for determining the propagation direction of slip events on faults over significant time periods limits our understanding of the long-term stability of fault slip propagation directions. A geological means for determining the propagation direction of slip events during the growth of faults is provided by mutually cross-cutting faults and bed-parallel slip-surfaces in the Ptolemais Basin, northern Greece.</p><p>In the Kardia lignite mine, Ptolemais Basin, bed-parallel slip surfaces intermittently offset the Quaternary faults as they grew to form discontinuities on otherwise continuous fault surfaces. Subsequent fault slip increments bypassed these discontinuities to re-establish a continuous fault trace and leave an associated ‘dead’ splay. The geometry and displacement distributions at these fault/bed-parallel slip intersections record the fault displacement at the time of bed-parallel slip and whether the next fault slip increment had an upwards or downwards component to its local propagation vector.</p><p>A database (N = 88) of slip propagation directions and fault throws was derived from continuous mapping of mine faces during lignite extraction over an eight year period. The data demonstrate a clear relationship between slip propagation direction and the accumulation of fault displacement on individual faults. During the early stages of fault growth, slip events propagated almost exclusively upwards through the mined sequence, but later stages of growth are marked by slip events showing both upward and downward components of propagation. The data therefore demonstrate that the location of the point of initiation of fault slip events on these Quaternary faults varied over the fault surfaces as the faults grew.</p><p>The emergence of systematic results from our analyses suggests that cross-cutting relationships between other synchronously active structures (e.g. conjugate faults) can provide a robust means for determining the propagation directions of slip events on ancient faults at outcrop.</p>

Laser-Induced Deformation Patterns in Thin Films and Surfaces

1999 ◽  
Vol 121 (2) ◽  
pp. 182-188 ◽  
Author(s):  
Daniel Walgraef
Keyword(s):  
Thin Films ◽  
Laser Irradiation ◽  
Surface Deformation ◽  
Laser Intensity ◽  
Laser Beams ◽  
Experimental Investigations ◽  
Relative Importance ◽  
Periodic Patterns ◽  
One Dimensional ◽  
Deformation Patterns

The coupling between surface deformation and defect motion may be at the origin of deformation patterns in thin films under laser irradiation. We analyze the dynamics of laser-induced vacancy densities and deformation fields and show how it triggers deformational instabilities, in the case of uniform and focused laser irradiation. Pattern selection analysis is performed, through linear, nonlinear, and numerical methods. In irradiation with extended beams, we show that, according to the relative importance of nonlinearities arising from the defect or from the bending dynamics, square, hexagonal or even quasi-periodic patterns are selected. It appears, furthermore, that one-dimensional gratings are always unstable in isotropic systems. In irradiation with focused laser beams, rose deformation patterns, with petal number increasing with laser intensity, naturally arise in this model, in qualitative agreement with experimental observations. These results claim for more systematic and quantitative experimental investigations of deformational pattern formation under laser irradiation.

scholarly journals Potential Fault Displacement Hazard Assessment Using Stochastic Source Models: A Retrospective Evaluation for the 1999 Hector Mine Earthquake

GeoHazards ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 398-414
Author(s):  
Katsuichiro Goda
Keyword(s):  
Hazard Analysis ◽  
Analysis Method ◽  
Fault Rupture ◽  
Displacement Vectors ◽  
Alternative Approach ◽  
Consistent Manner ◽  
Source Models ◽  
Fault Trace ◽  
Fault Displacement

Surface fault displacement due to an earthquake affects buildings and infrastructure in the near-fault area significantly. Although approaches for probabilistic fault displacement hazard analysis have been developed and applied in practice, there are several limitations that prevent fault displacement hazard assessments for multiple locations simultaneously in a physically consistent manner. This study proposes an alternative approach that is based on stochastic source modelling and fault displacement analysis using Okada equations. The proposed method evaluates the fault displacement hazard potential due to a fault rupture. The developed method is applied to the 1999 Hector Mine earthquake from a retrospective perspective. The stochastic-source-based fault displacement hazard analysis method successfully identifies multiple source models that predict fault displacements in close agreement with observed GPS displacement vectors and displacement offsets along the fault trace. The case study for the 1999 Hector Mine earthquake demonstrates that the proposed stochastic-source-based method is a viable option in conducting probabilistic fault displacement hazard analysis.

Structural controls on the emplacement and evacuation of magma from a sub-volcanic laccolith: Reyðarártindur Laccolith, SE Iceland

2021 ◽  
Author(s):  
Vincent Twomey ◽  
William McCarthy ◽  
Craig Magee
Keyword(s):  
Host Rock ◽  
Surface Deformation ◽  
Flow Direction ◽  
Volcanic Eruptions ◽  
Magma Ascent ◽  
Magma Flow ◽  
Existing Structures ◽  
Forced Folding ◽  
Deformation Patterns ◽  
Echelon Fault

<p>Laccoliths play a significant role in the transport and storage of magma in sub-volcanic systems. The construction and geometry of laccoliths can influence host rock and surface deformation patterns that may precede and provide warning of active magmatism and impending eruptions. Yet how laccolith construction and internal magma dynamics controls the location and form of magma ascent conduits (e.g., dykes and inclined sheets), which facilitate magma evacuation and may feed volcanic eruptions, remains poorly documented in natural examples.</p><p>The excellently exposed silicic, sub-volcanic Miocene Reyðarártindur Laccolith in SE Iceland offers an opportunity to investigate how magma ascent within inclined sheets, which emanated from the laccolith, related to intrusion construction and deformation in the surrounding host rock. We combine detailed structural mapping with anisotropy of magnetic susceptibility (AMS) analyses, which allow us to map magnetic rock fabrics that reflect magma flow patterns, to show that the laccolith comprises of several distinct magma lobes that intruded laterally towards the south-west. Each lobe intruded, inflated, and coalesced along a NE-SW primary axis facilitated by doming (i.e., forced folding) of the host rock. We also shown that pre-existing NNE-striking, left-stepping, en-echelon fault/fractures, as well as those generated during intrusion-induced host rock uplift, host moderately to steeply inclined rhyolitic/granophyric sheets that emanate from the lateral terminations of some flow lobes.</p><p>Based on the observed geometrical relationships between AMS fabrics and the sheet margins where magnetic foliations subparallel sheet contacts, or characterize an imbrication fabric, we suggest that magma evacuated moderately to steeply upward via these fault/fracture-controlled sheets. As these inclined sheets dip towards the laccolith, any eruptions they may have fed would have been laterally offset from the laccolith and any overlying surface deformation driven by forced folding. Our study shows that magma evacuation and ascent from laccoliths can be facilitated by inclined sheets that form at the lateral terminations of magma lobes that are spatially controlled by laccolith construction (e.g., flow direction and doming of the host rock) and the presence of pre-existing structures.</p>

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