scholarly journals The Bilila-Mtakataka fault in Malaŵi: An active, 100-km long, normal fault segment in thick seismogenic crust

Tectonics ◽  
1997 ◽  
Vol 16 (1) ◽  
pp. 137-150 ◽  
Author(s):  
James Jackson ◽  
Tom Blenkinsop
Keyword(s):  
Normal Fault ◽  
Fault Segment

scholarly journals Numerical analysis of interseismic, coseismic and postseismic phases for normal and reverse faulting earthquakes in Italy

2020 ◽  
Author(s):  
Matteo Albano ◽  
Salvatore Barba ◽  
Christian Bignami ◽  
Eugenio Carminati ◽  
Carlo Doglioni ◽  
...  
Keyword(s):  
Seismic Waves ◽  
Hanging Wall ◽  
Normal Fault ◽  
Ground Subsidence ◽  
Reverse Fault ◽  
Fault Segment ◽  
Elastic Load ◽  
Reverse Faulting ◽  
Common Framework ◽  
Postseismic Relaxation

Summary The preparation, initiation, and occurrence dynamics of earthquakes in Italy are governed by several frequently unknown physical mechanisms and parameters. Understanding these mechanisms is crucial for developing new techniques and approaches for earthquake monitoring and hazard assessments. Here, we develop a first-order numerical model simulating quasi-static crustal interseismic loading, coseismic brittle episodic dislocations, and postseismic relaxation for extensional and compressional earthquakes in Italy based on a common framework of lithostatic and tectonic forces. Our model includes an upper crust, where the fault is locked, and a deep crust, where the fault experiences steady shear. The results indicate that during the interseismic phase, the contrasting behavior between the upper locked fault segment and lower creeping fault segment generates a stretched volume at depth in the hanging wall via extensional tectonics while a contracted volume forms via compressional tectonics. The interseismic stress and strain gradients invert at the coseismic stage, with the interseismic dilated volume contracting during the coseismic stage, and vice versa. Moreover, interseismic stress gradients promote coseismic gravitational subsidence of the hanging wall for normal fault earthquakes and elastic uplift for reverse fault earthquakes. Finally, the postseismic relaxation is characterized by further ground subsidence and uplift for normal and reverse faulting earthquakes, respectively, which is consistent with the faulting style. The fault is the passive feature, with slipping generating the seismic waves, whereas the energy activating the movement is stored mostly in the hanging wall volume. The main source of energy for normal faulting and thrust is provided by the lithostatic load and elastic load, respectively.

scholarly journals Seismic and Geodetic Imaging (DInSAR) Investigation of the March 2021 Strong Earthquake Sequence in Thessaly, Central Greece

Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 311
Author(s):  
Gerassimos A. Papadopoulos ◽  
Apostolos Agalos ◽  
Andreas Karavias ◽  
Ioanna Triantafyllou ◽  
Issaak Parcharidis ◽  
...  
Keyword(s):  
Moment Tensor ◽  
Normal Fault ◽  
Surface Subsidence ◽  
Ground Subsidence ◽  
Fault Models ◽  
Strong Earthquakes ◽  
Fault Segment ◽  
Central Greece ◽  
Seismic Slip ◽  
Instrumental Period

Three strong earthquakes ruptured the northwest Thessaly area, Central Greece, on the 3, 4 and 12 March 2021. Since the area did not rupture by strong earthquakes in the instrumental period of seismicity, it is of great interest to understand the seismotectonics and source properties of these earthquakes. We combined relocated hypocenters, inversions of teleseismic P-waveforms and of InSAR data, and moment tensor solutions to produce three fault models. The first shock (Mw = 6.3) occurred in a fault segment of strike 314° and dip NE41°. It caused surface subsidence −40 cm and seismic slip 1.2–1.5 m at depth ~10 km. The second earthquake (Mw = 6.2) occurred to the NW on an antithetic subparallel fault segment (strike 123°, dip SW44°). Seismic slip of 1.2 m occurred at depth of ~7 km, while surface subsidence −10 cm was determined. Possibly the same fault was ruptured further to the NW on 12 March (Mw = 5.7, strike 112°, dip SSW42°) that caused ground subsidence −5 cm and seismic slip of 1.0 m at depth ~10 km. We concluded that three blind, unknown and unmapped so far normal fault segments were activated, the entire system of which forms a graben-like structure in the area of northwest Thessaly.

scholarly journals Nonlinear fault damage zone scaling revealed through analog modeling

Geology ◽  
2021 ◽  
Author(s):  
Sylvain Mayolle ◽  
Roger Soliva ◽  
Stéphane Dominguez ◽  
Christopher Wibberley ◽  
Yannick Caniven
Keyword(s):  
Failure Modes ◽  
Damage Zone ◽  
Normal Fault ◽  
Fault Segment ◽  
Mechanical Unit ◽  
Analog Modeling ◽  
Fault Damage Zone ◽  
Fault Growth ◽  
Fault Displacement ◽  
Zone Growth

Fault damage zones strongly influence fluid flow and seismogenic behavior of faults and are thought to scale linearly with fault displacement until reaching a threshold thickness. Using analog modeling with different frictional layer thicknesses, we investigate damage zone dynamic evolution during normal fault growth. We show that experimental damage zone growth with displacement is not linear but progressively tends toward a threshold thickness, being larger in the thicker models. This threshold thickness increases significantly at fault segment relay zones. As the thickness threshold is approached, the failure mode progressively transitions from dilational shear to isochoric shear. This process affects the whole layer thickness and develops as a consequence of fault segment linkage as inferred in nature when the fault matures. These findings suggest that fault damage zone widths are limited both by different scales of mechanical unit thickness and the evolution of failure modes, ultimately controlled in nature by lithology and deformation conditions.

scholarly journals SEGMENTATION AND INTERACTION OF NORMAL FAULTS IN CENTRAL GREECE

2017 ◽  
Vol 43 (1) ◽  
pp. 428 ◽  
Author(s):  
S. Kokkalas
Keyword(s):  
Scaling Laws ◽  
Normal Fault ◽  
Fault Zones ◽  
Segment Length ◽  
Normal Faults ◽  
Mechanical Interaction ◽  
Fault Segment ◽  
Central Greece ◽  
Fault Length ◽  
Radial Propagation

The aim of this study is to improve our understanding on the mechanical interaction and linkage process between normal fault segments. Faults grow by the process of radial propagation and the linkage of segments, as strain increases, evolving to large fault systems. For this purpose we conducted a combined field and photogeological study on two major segmented fault zones in Central Greece, the Atalanti and Arkitsa fault zones. This approach includes effects of fault size and spatial distribution, scaling laws and footwall-hanginwall topography. Throw distribution and the geometry of the segmented fault arrays were analyzed in order to investigate the complexity of fault zones, the fault linkage process and the geometric characteristics of the relay zones formed between individual segments. The correlation of fault throw with fault length (D-L) and the ratios of overlap-separation (OL-S), separation-fault segment length (S-L) and relay displacement vs. separation (Dr-S) were examined in order to give an insight for fault segment interaction and linkage .

THE EVOLUTION OF SUBSIDIARY FRACTURE NETWORKS IN SEGMENTED NORMAL FAULT SYSTEMS

2016 ◽  
Author(s):  
Samuel O. Simoneau ◽  
◽  
Benjamin Surpless ◽  
Hannah Mathy
Keyword(s):  
Normal Fault ◽  
Fracture Networks ◽  
Fault Systems
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