Synthesis of seismicity studies for western Alaska

Biswas, N. N.; Pujol, José; Tytgat, Guy; Dean, Kenneth

doi:10.1016/0040-1951(86)90183-6

Cited by 8 publications

(5 citation statements)

References 19 publications

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“…Nome is located near the Bering Strait where seismicity levels are relatively high (e.g. Biswas et al 1986). Seismicity here possibly delineates the northeastern boundary of the proposed independent 'Bering block' (Mackey et al 1997).…”

Section: Pacific-north Americamentioning

confidence: 99%

An integrated global model of present-day plate motions and plate boundary deformation

Kreemer¹,

Holt²,

Haines

2003

Geophysical Journal International

567

469

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SUMMARY In this paper we present a global model (GSRM‐1) of both horizontal velocities on the Earth's surface and horizontal strain rates for almost all deforming plate boundary zones. A model strain rate field is obtained jointly with a global velocity field in the process of solving for a global velocity gradient tensor field. In our model we perform a least‐squares fit between model velocities and observed geodetic velocities, as well as between model strain rates and observed geological strain rates. Model velocities and strain rates are interpolated over a spherical Earth using bi‐cubic Bessel splines. We include 3000 geodetic velocities from 50 different, mostly published, studies. Geological strain rates are obtained for central Asia only and they are inferred from Quaternary fault slip rates. For all areas where no geological information is included a priori constraints are placed on the style and direction (but not magnitude) of the model strain rate field. These constraints are taken from a seismic strain rate field inferred from (normalized) focal mechanisms of shallow earthquakes. We present a global solution of the second invariant of the model strain rate field as well as strain rate solutions for a few selected plate boundary zones. Generally, the strain rate tensor field is consistent with geological and seismological data. With the assumption of plate rigidity for all areas other than the plate boundary zones we also present relative angular velocities for most plate pairs. We find that in general there is a good agreement between the present‐day plate motions we obtain and long‐term plate motions, but a few significant differences exist. The rotation rates for the Indian, Arabian and Nubian plates relative to Eurasia are 30, 13 and 50 per cent slower than the NUVEL‐1A estimate, respectively, and the rotation rate for the Nazca Plate relative to South America is 17 per cent slower. On the other hand, Caribbean–North America motion is 76 per cent faster than the NUVEL‐1A estimate. While crustal blocks in the India–Eurasia collision zone move significantly and self‐consistently with respect to bounding plates, only a very small motion is predicted between the Nubian and Somalian plates. By integrating plate boundary zone deformation with the traditional modelling of angular velocities of rigid plates we have obtained a model that has already been proven valuable in, for instance, redefining a no‐net‐rotation model of surface motions and by confirming a global correlation between seismicity rates and tectonic moment rates along subduction zones and within zones of continental deformation.

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Section: Pacific-north Americamentioning

confidence: 99%

An integrated global model of present-day plate motions and plate boundary deformation

Kreemer¹,

Holt²,

Haines

2003

Geophysical Journal International

567

469

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“…During the Late Jurassic and Early Cretaceous, the Arctic Alaska‐Chukotka terrane underwent arc‐continent collision and partial subduction [ Plafker and Berg , ; Till and Dumoulin , ], and subsequent granitic plutonism and metamorphism during a Cretaceous episode of extension and gneiss dome formation [ Amato et al ., ; Miller et al ., ]. Since these events, there has been a progressive tectonic reorganization to a N‐S extensional regime in western Alaska (Figure ), as revealed by seismicity and young normal fault orientation [ Biswas et al ., ; Dumitru et al ., ; Mackey et al ., ; Redfield et al ., ].…”

Section: Geological and Tectonic Settingmentioning

confidence: 99%

“…Focal mechanisms from Biswas et al . [] and Fujita et al [] show the Seward Peninsula to be a region of N‐S extension in recent time. Seismicity extends into the Chukotka Peninsula of Russia and outlines the edges of a rigid Bering Sea block (Figure ) which is undergoing clockwise rotation probably as a response to terrane accretion in southeastern Alaska and tectonic extrusion along the Denali and Tintina strike‐slip faults [ Fujita et al ., ; Mackey et al ., ].…”

Section: The Bendeleben Faultmentioning

confidence: 99%

“…Small earthquakes (<4.0 M) are most common on the Seward Peninsula, although several ranging from 4.0 to 5.9, and one 6.0 to 6.9 M event have occurred [Fujita et al, 2002]. Focal mechanisms from Biswas et al [1986] and Fujita et al [2002] show the Seward Peninsula to be a region of N-S extension in recent time. Seismicity extends into the Chukotka Peninsula of Russia and outlines the edges of a rigid Bering Sea block ( Alaska and tectonic extrusion along the Denali and Tintina strike-slip faults [Fujita et al, 2002;Mackey et al, 1997].…”

Section: The Bendeleben Faultmentioning

confidence: 99%

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Thermochronologic constraints on Late Cretaceous to Cenozoic exhumation of the Bendeleben Mountains, Seward Peninsula, Alaska

McDannell

Toro

Hourigan

et al. 2014

Geochem. Geophys. Geosyst.

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In the Bendeleben Mountains, Seward Peninsula, mid-Cretaceous granites are exposed in an uplifted block bounded on its south side by an E-W striking normal fault. The Bendeleben fault has wellpreserved scarps 4-7 m in height that offset Holocene moraines. Seismic activity, young normal faulting, and Quaternary basaltic volcanism are all evidence of active extension. South of the Bendeleben fault, there is a 3-4 km deep basin. Fifteen apatite (U-Th)/He ages from granitic samples of the footwall yield an Eocene weighted mean age of 41.364.8 Ma. Biotite 40 Ar/ 39 Ar ages from the country rock of the Bendeleben pluton are 81-83 Ma. In spite of the young fault scarps, HeFTy and Pecube thermal modeling results illustrate that rapid exhumation of the Bendeleben Mountains occurred in the Late Cretaceous-Eocene and slowed since the Oligocene. A weak age-elevation relationship of apatite He ages and a lack of correlation between age and distance from the fault indicate that exhumation was accomplished with minimal block rotation on a steeply dipping, long-lived normal fault. Timing of extension in the Seward Peninsula can be correlated with deformation in the offshore Hope Basin where seismic reflection lines document Early Tertiary largemagnitude normal faulting followed by minor post-Miocene reactivation. The faulting observed in the Bendeleben Mountains is part of an extensional system that spans a large portion of the Bering Strait region. The tectonic model proposed in previous studies suggests that clockwise rotation of the Bering block relative to North America is the cause of extensional deformation in western Alaska.

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“…Researchers have studied the Alaska subduction zone from different points of view for several years (Biswas et al, 1986;Doser and Rodriguez, 2011;Smith and Tape, 2019;Daly et al, 2021;Qu et al, 2022). The present article follows a different line to previous works as we will present an analytical approach based on the on the variations of the entropy in catalogs of magnitudes and intervals.…”

Section: Introductionmentioning

confidence: 99%

2021 Alaska Earthquake: entropy approach to its precursors and aftershock regimes

Vogel,

Pastén,

Saravia

et al. 2024

Preprint

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Abstract. For the first time, an entropy analysis has been made in Alaska, a seismic-rich region located in a subduction zone that shows a nontrivial behavior: the subduction arc changes the seismic activity from the eastern zone to the western zone, showing a decrease in this activity along the subduction. We analyze this zone through the Tsallis entropy and the mutability (or dynamic entropy). The data set used for this analysis was measured between 2000 and 2023, considering 19549 seismic events. We have found an agreement between the results for the two entropies. We have followed the value of the q parameter of the Tsallis entropy, finding values between 1.70 and 1.85, in concordance with values previously found in other seismic regions of the planet. Also, the values of the q-parameter tend to decrease over time but show an increase before the main earthquakes. Mutability also shows a tendency to decrease over time and an increase previous to the main earthquakes. To deeply analyze this zone, we divided the region into four sub-zones. The results show how mutability can identify the seismic activity in each zone. This study shows how an entropy approach can shed light on understanding the seismicity in subduction zones.

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Synthesis of seismicity studies for western Alaska

Cited by 8 publications

References 19 publications

An integrated global model of present-day plate motions and plate boundary deformation

An integrated global model of present-day plate motions and plate boundary deformation

Thermochronologic constraints on Late Cretaceous to Cenozoic exhumation of the Bendeleben Mountains, Seward Peninsula, Alaska

2021 Alaska Earthquake: entropy approach to its precursors and aftershock regimes

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