Holocene Vertical Displacement on the Central Segments of the Wasatch Fault Zone, Utah

AbstractThe Southern Andes are often viewed as a classic example for kinematic partitioning of oblique plate convergence into components of continental margin-parallel strike-slip and transverse shortening. In this regard, the Liquiñe-Ofqui Fault Zone, one of Earth’s most prominent intra-arc deformation zones, is believed to be the most important crustal discontinuity in the Southern Andes taking up margin-parallel dextral strike-slip. Recent structural studies, however, are at odds with this simple concept of kinematic partitioning, due to the presence of margin-oblique and a number of other margin-parallel intra-arc deformation zones. However, knowledge on the extent of such zones in the Southern Andes is still limited. Here, we document traces of prominent structural discontinuities (lineaments) from the Southern Andes between 39° S and 46° S. In combination with compiled low-temperature thermochronology data and interpolation of respective exhumation rates, we revisit the issue of kinematic partitioning in the Southern Andes. Exhumation rates are maximal in the central parts of the orogen and discontinuity traces, trending predominantly N–S, WNW–ESE and NE–SW, are distributed across the entire width of the orogen. Notably, discontinuities coincide spatially with large gradients in Neogene exhumation rates and separate crustal domains characterized by uniform exhumation. Collectively, these relationships point to significant components of vertical displacement on these discontinuities, in addition to horizontal displacements known from published structural studies. Our results agree with previously documented Neogene shortening in the Southern Andes and indicate orogen-scale transpression with maximal vertical extrusion of rocks in the center of the transpression zone. The lineament and thermochronology data call into question the traditional view of kinematic partitioning in the Southern Andes, in which deformation is focused on the Liquiñe-Ofqui Fault Zone.

Seismic Activity of the Manisa Fault Zone in Western Turkey Constrained by Cosmogenic 36Cl Dating

Geosciences ◽

10.3390/geosciences11110451 ◽

2021 ◽

Vol 11 (11) ◽

pp. 451

Author(s):

Nasim Mozafari ◽

Çağlar Özkaymak ◽

Dmitry Tikhomirov ◽

Susan Ivy-Ochs ◽

Vasily Alfimov ◽

...

Keyword(s):

Fault Zone ◽

Normal Fault ◽

Vertical Displacement ◽

Historical Records ◽

Western Turkey ◽

Slip Rates ◽

Vertical Displacements ◽

Surface Ruptures ◽

Fault Scarps ◽

Calculated Average

This study reports on the cosmogenic 36Cl dating of two normal fault scarps in western Turkey, that of the Manastır and Mugırtepe faults, beyond existing historical records. These faults are elements of the western Manisa Fault Zone (MFZ) in the seismically active Gediz Graben. Our modeling revealed that the Manastır fault underwent at least two surface ruptures at 3.5 ± 0.9 ka and 2.0 ± 0.5 ka, with vertical displacements of 3.3 ± 0.5 m and 3.6 ± 0.5 m, respectively. An event at 6.5 ± 1.6 ka with a vertical displacement of 2.7 ± 0.4 m was reconstructed on the Mugırtepe fault. We attribute these earthquakes to the recurring MFZ ruptures, when also the investigated faults slipped. We calculated average slip rates of 1.9 and 0.3 mm yr−1 for the Manastır and Mugırtepe faults, respectively.

Surface faulting along the Superstition Hills fault zone and nearby faults associated with the earthquakes of 24 November 1987

Bulletin of the Seismological Society of America ◽

10.1785/bssa0790020252 ◽

1989 ◽

Vol 79 (2) ◽

pp. 252-281

Author(s):

R. V. Sharp ◽

K. E. Budding ◽

J. Boatwright ◽

M. J. Ader ◽

M. G. Bonilla ◽

...

Keyword(s):

Fault Zone ◽

Lateral Displacement ◽

Vertical Displacement ◽

Repeated Measurements ◽

The South ◽

Surface Rupture ◽

Imperial Valley ◽

The North ◽

South Central ◽

The Right

Abstract The M 6.2 Elmore Desert Ranch earthquake of 24 November 1987 was associated spatially and probably temporally with left-lateral surface rupture on many northeast-trending faults in and near the Superstition Hills in western Imperial Valley. Three curving discontinuous principal zones of rupture among these breaks extended northeastward from near the Superstition Hills fault zone as far as 9 km; the maximum observed surface slip, 12.5 cm, was on the northern of the three, the Elmore Ranch fault, at a point near the epicenter. Twelve hours after the Elmore Ranch earthquake, the M 6.6 Superstition Hills earthquake occurred near the northwest end of the right-lateral Superstition Hills fault zone. Surface rupture associated with the second event occurred along three strands of the zone, here named North and South strands of the Superstition Hills fault and the Wienert fault, for 27 km southeastward from the epicenter. In contrast to the left-lateral faulting, which remained unchanged throughout the period of investigation, the right-lateral movement on the Superstition hills fault zone continued to increase with time, a behavior that was similar to other recent historical surface ruptures on northwest-trending faults in the Imperial Valley region. We measured displacements over 339 days at as many as 296 sites along the Superstition Hills fault zone, and repeated measurements at 49 sites provided sufficient data to fit with a simple power law. Data for each of the 49 sites were used to compute longitudinal displacement profiles for 1 day and to estimate the final displacement that measured slips will approach asymptotically several years after the earthquakes. The maximum right-lateral slip at 1 day was about 50 cm near the south-central part of the North strand of Superstition Hills fault, and the predicted maximum final displacement is probably about 112 cm at Imler Road near the center of the South strand of the Superstition Hills fault. The overall distributions of right-lateral displacement at 1 day and the estimated final slip are nearly symmetrical about the midpoint of the surface rupture. The average estimated final right-lateral slip for the Superstition Hills fault zone is about 54 cm. The average left-lateral slip for the conjugate faults trending northeastward is about 23 cm. The southernmost ruptured member of the Superstition Hills fault zone, newly named the Wienert fault, extends the known length of the zone by about 4 km. The southern half of this fault, south of New River, expressed only vertical displacement on a sinuous trace. The maximum vertical slip by the end of the observation period there was about 25 cm, but its growth had not ceased. Photolineaments southeast of the end of new surface rupture suggest continuation of the Superstition Hills fault zone in farmland toward Mexico.

Rupture characteristics of normal faults: an example from the Wasatch fault zone, Utah

Geological Society London Special Publications ◽

10.1144/gsl.sp.1987.028.01.21 ◽

1987 ◽

Vol 28 (1) ◽

pp. 337-353 ◽

Cited By ~ 9

Author(s):

Ronald L. Bruhn ◽

Pamela R. Gibler ◽

William T. Parry

Keyword(s):

Fault Zone ◽

Normal Faults ◽

Wasatch Fault

Reevaluation of Holocene faulting at the Kaysville site, Weber segment of the Wasatch fault zone, Utah

Tectonics ◽

10.1029/93tc02067 ◽

1994 ◽

Vol 13 (1) ◽

pp. 1-16 ◽

Cited By ~ 27

Author(s):

James P. McCalpin ◽

Steven L. Forman ◽

Mike Lowe

Keyword(s):

Fault Zone ◽

Wasatch Fault