Fault displacement gradients on normal faults and associated deformation

AAPG Bulletin ◽  
2014 ◽  
Vol 98 (6) ◽  
pp. 1161-1184 ◽  
Author(s):  
Alan P. Morris ◽  
Ronald N. McGinnis ◽  
David A. Ferrill
Keyword(s):  
Normal Faults ◽  
Fault Displacement

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>

scholarly journals Distributed faulting following normal earthquakes: reassessment and updating of scaling relations

2020 ◽  
Author(s):  
Maria Francesca Ferrario ◽  
Franz Livio
Keyword(s):  
Normal Faults ◽  
Scaling Relations ◽  
Engineering Practice ◽  
Probabilistic Assessment ◽  
Logic Tree ◽  
Case Histories ◽  
Full Spectrum ◽  
Empirical Relations ◽  
Fault Displacement ◽  
Tree Approach

Abstract. Coseismic surface faulting is a significant source of hazard for critical plants and distributive infrastructures; it may occur either on the primary fault, or as distributed rupture on nearby faults. Hazard assessment for distributed faulting is based on empirical relations which, in the case of normal faults, were derived almost 15 years ago on a dataset of US earthquakes. We collect additional case histories worldwide, for a total of 21 earthquakes, and we calculate the conditional probability of distributed faulting as a function of distance from the primary fault. We found no clear dependency on the magnitude nor the time of occurrence of the earthquakes, but our data consistently show a higher probability of rupture when compared to the scaling relations currently adopted in engineering practice. We derive updated empirical regressions and show that results are strongly conditioned by the averaging of earthquakes effectively generating distributed faulting at a given distance and those which did not generate faulting; thus, we introduce a more conservative scenario, which can be included in a logic tree approach to consider the full spectrum of potential ruptures. Our results can be applied in the framework of probabilistic assessment of fault displacement hazard.

Gravity data as a tool for detecting faults: In-depth enhancement of subtle Almada’s basement faults, Brazil

Geophysics ◽  
2007 ◽  
Vol 72 (3) ◽  
pp. B59-B68 ◽  
Author(s):  
Valeria C. Barbosa ◽  
Paulo T. Menezes ◽  
João B. Silva
Keyword(s):  
Gravity Data ◽  
Synthetic Data ◽  
Normal Fault ◽  
Northeastern Brazil ◽  
Normal Faults ◽  
Gravity Inversion ◽  
Inversion Method ◽  
Basement Faults ◽  
Depth Enhancement ◽  
Fault Displacement

We demonstrate the potential of gravity data to detect and to locate in-depth subtle normal faults in the basement relief of a sedimentary basin. This demonstration is accomplished by inverting the gravity data with the constraint that the estimated basement relief presents local abrupt faults and is smooth elsewhere. We inverted the gravity data from the onshore Almada Basin in northeastern Brazil, and we mapped several normal faults whose locations and plane geometries were already known from seismic imaging. The inversion method delineated well both the discontinuities with small or large slips and a sequence of step faults. Using synthetic data, we performed a systematic search of normal fault slips versus fault displacement depths to map the fault-detectable region in this space. This mapping helps to assess the ability of gravity inversion to detect normal faults. Mapping shows that normal faults with small [Formula: see text], medium (about [Formula: see text]), and large (about [Formula: see text]) vertical slips can be detected if the maximum midpoint depths of the fault planes are smaller than 1.8, 3.8, and [Formula: see text], respectively.

scholarly journals Conditional probability of distributed surface rupturing during normal-faulting earthquakes

Solid Earth ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 1197-1209
Author(s):  
Maria Francesca Ferrario ◽  
Franz Livio
Keyword(s):  
Conditional Probability ◽  
Normal Faults ◽  
Engineering Practice ◽  
Normal Faulting ◽  
Logic Tree ◽  
Case Histories ◽  
Full Spectrum ◽  
Empirical Relations ◽  
Fault Displacement ◽  
Tree Approach

Abstract. Coseismic surface faulting is a significant source of hazard for critical plants and distributive infrastructure; it may occur either on the principal fault or as distributed rupture on nearby faults. Hazard assessment for distributed faulting is based on empirical relations which, in the case of normal faults, were derived almost 15 years ago using a dataset of US earthquakes. We collected additional case histories worldwide, for a total of 21 earthquakes, and calculated the conditional probability of distributed faulting as a function of distance from the principal fault. We found no clear dependency on the magnitude nor the time of occurrence of the earthquakes, but our data consistently show a higher probability of rupture when compared with the scaling relations currently adopted in engineering practice. We derive updated empirical regressions and show that the results are strongly conditioned by the averaging of earthquakes effectively generating distributed faulting at a given distance and those which did not generate faulting; thus, we introduce a more conservative scenario that can be included in a logic tree approach to consider the full spectrum of potential ruptures. Our results can be applied in the framework of probabilistic assessment of fault displacement hazard.

scholarly journals Offshore bedrock geology of Eclipse Sound and Pond Inlet: connecting the structure and stratigraphy of Bylot and northern Baffin islands

2020 ◽  
Vol 57 (10) ◽  
pp. 1254-1267
Author(s):  
Lisel D. Currie ◽  
Tom A. Brent ◽  
Elizabeth C. Turner
Keyword(s):  
Fault Zone ◽  
Active Faults ◽  
Petroleum Exploration ◽  
Normal Faults ◽  
Sea Floor ◽  
Baffin Bay ◽  
Bay Area ◽  
History Of ◽  
Marine Seismic ◽  
Fault Displacement

Understanding the Mesoproterozoic and younger structural history of the Eclipse Sound/Pond Inlet area is essential for the interpretation of its Archean to Paleoproterozoic geological history and could have important implications for mineral and petroleum exploration models in the northern Baffin Bay area. The identification of potentially active faults is critical for understanding possible earthquake-related hazards in the area. The integrated interpretation of 1970s-vintage marine seismic data with hill-shaded bathymetry, aeromagnetic data, and onshore geology maps has facilitated the identification of probable Mesoproterozoic (Bylot Supergroup) to Holocene strata on and below the sea floor and a suite of episodically reactivated northwest-striking horst- and graben-bounding normal faults and fault zones. Fault displacement likely occurred during the development of the Mesoproterozoic Borden basin and the Cretaceous–Paleogene opening of Baffin Bay, and in some cases may continue today. Some faults become more west-trending toward the south, which requires parts of these faults to have intermittently accommodated transtensional and (or) transpressional motion, possibly explaining local folds and out-of-graben thrusting. Numerous previously unrecognised faults have been documented, with faults beneath Eclipse Sound (Eclipse Trough) spaced at 5 to 7 km intervals, and at least one fault zone (Cape Hay Fault Zone) that appears to be at least 250 km in length, suggesting faults of similar spacing and scale may be present under Baffin Bay. This study uses a multi-thematic office-based methodology that inexpensively, and with little environmental impact, facilitates the mapping of structures that intersect the sea floor in areas where glaciers have exposed bedrock.

Deformed streams reveal growth and linkage of a normal fault array in the Canyonlands graben, Utah

Geology ◽  
2005 ◽  
Vol 33 (8) ◽  
pp. 645-648 ◽  
Author(s):  
Deirdre Commins ◽  
Sanjeev Gupta ◽  
Joseph Cartwright
Keyword(s):  
Normal Fault ◽  
Initial Component ◽  
Length Ratio ◽  
Normal Faults ◽  
Fault Interaction ◽  
Single Fault ◽  
Coupling Fault ◽  
Fault Displacement ◽  
Interaction Phase

Abstract We use the deformation of streams by the growth of active normal faults within the Canyonlands graben of southeastern Utah to constrain the displacement evolution of a fault array during segment interaction and linkage. Coupling fault displacement data with geomorphic analysis of present-day streams and paleostreams permits sequential reconstruction of a three-segment fault array from initial component segments to its final displacement geometry. Our results show that although segment interaction causes enhanced displacement addition at overlap zones, postlinkage displacement accumulation is significant and permits array equilibration to a displacement-length ratio characteristic of a single fault. Evidence of stream disequilibrium indicates that this postlinkage displacement addition was rapid compared to that during the fault interaction phase.

Estimating the slip rates of normal faults in the Great Basin, USA

2000 ◽  
Vol 12 (3-4) ◽  
pp. 227-240 ◽  
Author(s):  
C. M. dePolo ◽  
J. G. Anderson
Keyword(s):  
Great Basin ◽  
Normal Faults ◽  
Slip Rates
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