Geometric pattern, rupture termination and fault segmentation of the Dixie Valley—Pleasant Valley active normal fault system, Nevada, U.S.A.

On March 3, 2021, a strong (Mw6.3) earthquake occurred near the towns of Tyrnavos and Elassona. One day later (March 4), a second strong (Mw6.0) earthquake occurred just a few kilometres toward the WNW. The aftershock spatial distribution and the focal mechanisms revealed NW-SE-striking normal faulting. The focal mechanisms also revealed a NE-SW oriented extensional stress field, different from the orientation we knew so far (ca. N-S). The magnitude and location of the two strongest shocks, and the spatiotemporal evolution of the sequence, strongly suggest that two adjacent fault segments were ruptured respectively. The sequence was followed by several coseismic ground deformational phenomena, such as landslides/rockfalls, liquefaction and ruptures. The landslides and rockfalls were mostly associated with the ground shaking. The ruptures were observed west of the Titarissios River, near to the Quaternary faults found by bore-hole lignite investigation. In the same direction, a fault scarp separating the alpidic basement from the alluvial deposits of the Titarissios valley implies the occurrence of a well-developed fault system. Some of the ground ruptures were accompanied by extensive liquefaction phenomena. Others cross-cut reinforced concrete irrigation channels without changing their direction. We suggest that this fault system was partially reactivated, as a secondary surface rupture, during the sequence as a steeper splay of a deeper low-to-moderate angle normal fault.

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The 31 March 2020 Mw 6.5 Stanley, Idaho, Earthquake: Seismotectonics and Preliminary Aftershock Analysis

Seismological Research Letters ◽

10.1785/0220200319 ◽

2020 ◽

Author(s):

Lee M. Liberty ◽

Zachery M. Lifton ◽

T. Dylan Mikesell

Keyword(s):

Surface Displacement ◽

Volcanic Belt ◽

Normal Fault ◽

Fault System ◽

Basin And Range Province ◽

Ground Shaking ◽

The North ◽

Show Evidence ◽

Tectonic Framework ◽

Tectonic Belt

Abstract We report on the tectonic framework, seismicity, and aftershock monitoring efforts related to the 31 March 2020 Mw 6.5 Stanley, Idaho, earthquake. The earthquake sequence has produced both strike-slip and dip-slip motion, with minimal surface displacement or damage. The earthquake occurred at the northern limits of the Sawtooth normal fault. This fault separates the Centennial tectonic belt, a zone of active seismicity within the Basin and Range Province, from the Idaho batholith to the west and Challis volcanic belt to the north and east. We show evidence for a potential kinematic link between the northeast-dipping Sawtooth fault and the southwest-dipping Lost River fault. These opposing faults have recorded four of the five M≥6 Idaho earthquakes from the past 76 yr, including 1983 Mw 6.9 Borah Peak and the 1944 M 6.1 and 1945 M 6.0 Seafoam earthquakes. Geological and geophysical data point to possible fault boundary segments driven by pre-existing geologic structures. We suggest that the limits of both the Sawtooth and Lost River faults extend north beyond their mapped extent, are influenced by the relic trans-Challis fault system, and that seismicity within this region will likely continue for the coming years. Ongoing seismic monitoring efforts will lead to an improved understanding of ground shaking potential and active fault characteristics.

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THREE-DIMENSIONAL ANALYSIS OF NORMAL FAULT ZONES IN KARDIA MINE, PTOLEMAIS BASIN, NW GREECE

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.21340 ◽

2016 ◽

Vol 50 (1) ◽

pp. 15 ◽

Cited By ~ 1

Author(s):

E. Delogkos ◽

T Manzocchi ◽

C. Childs ◽

C. Sachanidis ◽

T. Barmpas ◽

...

Keyword(s):

Three Dimensional ◽

Normal Fault ◽

3D Models ◽

Fault Zones ◽

System Structure ◽

Open Pit ◽

Fault System ◽

Zone Structure ◽

Geological Interpretation ◽

Lignite Mine

Six normal fault zones, with throws ranging from a few meters up to 50 m, were studied within an active, open pit, lignite mine in Ptolemais. Each fault was mapped 20 times over a period of five years because at intervals of ca. 3 months working faces are taken back between 20 and 50 m exposing fresh fault outcrops for mapping.Various resolutions of photographs and structural measurements were imported into a fully georeferenced 3D structural interpretation package, resulting in aseismic scale and outcrop resolution 3D fault volume with outcrop and panoramic photographs acting as the seismic sections in equivalent seismic surveys. Low resolution 3D models for the fault system structure at mine scale and higher-resolution 3D models for the fault zone structure were produced after geological interpretation and they can be used for qualitative and quantitative analysis.

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Workflow of Digital Field Mapping and Drone-Aided Survey for the Identification and Characterization of Capable Faults: The Case of a Normal Fault System in the Monte Nerone Area (Northern Apennines, Italy)

ISPRS International Journal of Geo-Information ◽

10.3390/ijgi9110616 ◽

2020 ◽

Vol 9 (11) ◽

pp. 616

Author(s):

Mauro De Donatis ◽

Mauro Alberti ◽

Mattia Cipicchia ◽

Nelson Muñoz Guerrero ◽

Giulio F. Pappafico ◽

...

Keyword(s):

Central Italy ◽

Three Dimensional ◽

Normal Fault ◽

Field Work ◽

Digital Data ◽

Fault System ◽

Seismic Profiles ◽

Postgraduate Students ◽

Recent Earthquakes

Field work on the search and characterization of ground effects of a historical earthquake (i.e., the Cagli earthquake in 1781) was carried out using terrestrial and aerial digital tools. The method of capturing, organizing, storing, and elaborating digital data is described herein, proposing a possible workflow starting from pre-field project organization, through reiteration of field and intermediate laboratory work, to final interpretation and synthesis. The case of one of the most important seismic events in the area of the northern Umbria–Marche Apennines provided the opportunity to test the method with both postgraduate students and researchers. The main result of this work was the mapping of a capable normal fault system with a great number of observations, as well as a large amount of data, from difficult outcrop areas. A GIS map and a three-dimensional (3D) model, with the integration of subsurface data (i.e., seismic profiles and recent earthquake distribution information), allowed for a new interpretation of an extensional tectonic regime of this Apennines sector, similar to one of the southernmost areas of central Italy where recent earthquakes occurred on 2016.

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L'evolution tectonique post-hercynienne de la bordure mesozoique des Cevennes meridionales entre Ales et Ganges

BSGF - Earth Sciences Bulletin ◽

10.2113/gssgfbull.s7-vii.1.85 ◽

1965 ◽

Vol S7-VII (1) ◽

pp. 85-92 ◽

Cited By ~ 2

Author(s):

Michel Seguret ◽

Francois Proust

Keyword(s):

Normal Fault ◽

Late Eocene ◽

Fault System ◽

System Movement

Abstract The southeast edge of the Central Massif, between the Rhone and Herault valleys (France), is an area of Mesozoic rocks cut by a NE-SW fault system. Movement along the faults has been recurrent and from the Triassic through the succeeding Mesozoic, uplift and downwarp resulted in local basins and troughs accumulating distinct sedimentary suites. Intense compressive movements associated with the Pyrenean revolution during the late Eocene produced complex folds and overthrusts imposed upon the normal fault system. Continuation of the activity contributed to the complexity of the structures during the Oligocene. No evidence was found, during recent studies, to support the theory of allochthonous movements during the Oligocene.

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