Active faults and seismic hazards in Alaska

Koehler, Richard; Carver, Gary A.

doi:10.14509/29705

Cited by 21 publications

(16 citation statements)

References 42 publications

(64 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our analysis corroborates previous studies (Koehler et al., 2018; Nokleberg et al., 1985; Stout, 1976) demonstrating no clear evidence for Quaternary deformation in the Broxson Gulch thrust system. Although the Rainy Creek fault and associated footwall folds in the structurally lowest position of the thrust system generally coincide with the range front, local post‐glacial escarpments along the range front display paired headwall and toe features that are more consistent with slumping rather than tectonic surface deformation and attest to the previously inferred high potential for recent geomorphic resurfacing (Koehler et al., 2018; Figure S1). However, some features of the geologic framework require post‐Miocene deformation, including deformation of ≤6 Ma foreland basin strata (Waldien, Roeske, Benowitz, et al., 2021) and one AHe cooling age of ca.…”

Section: Discussionsupporting

confidence: 92%

Suture Reactivation, Slip Partitioning, and a Protracted Strike‐Slip Rate Gradient in the Denali Fault System, Southern Alaska, USA

Waldien,

Roeske,

Chatterjee

et al. 2023

Tectonics

View full text Add to dashboard Cite

Active strike‐slip fault systems commonly display along‐strike Quaternary slip rate gradients associated with fault bends and splay faults, which generate surface uplift by dip‐slip faulting or distributed “off fault” deformation. By analogy, the documentation of long‐term (107 yr) slip gradients on some continental strike‐slip fault systems implies long‐term coevolution of strike‐slip and dip‐slip fault systems. Here we leverage the observed ≥33 Myr right‐lateral slip gradient on the Denali fault, Alaska, USA to investigate the role of splay thrust systems in accommodating the slip gradient. We focus on the Broxson Gulch thrust system, which splays southwestward from the Denali fault in the eastern Alaska Range. Apatite and zircon (U‐Th)/He and fission‐track cooling ages from metasedimentary and metaplutonic rocks intersected by the thrust system record an along‐strike decrease in cooling ages commensurate with an increase in late Oligocene‐Neogene bedrock exhumation and shortening with proximity to the Denali fault. The dominant structure in the Broxson Gulch thrust system is the Valdez Creek fault, which is an upper crustal reactivation of the Valdez Creek shear zone–the main Late Cretaceous suture between western North America and outboard accreted arc terranes. After reactivation of the Valdez Creek shear zone at ca. 30 Ma, the thrust system grew by south‐vergent imbrication of the upper crust along thrust and reverse faults until at least 6 Ma. Incorporating results from the Broxson Gulch thrust system into the regional structural evolution of the Denali fault system reveals significant spatiotemporal heterogeneity in shortening adjacent to the Denali fault. Moreover, nearly all of the late Oligocene‐Neogene shortening south of the Denali fault was focused along reactivated terrane boundaries inherited from Mesozoic assembly of the North American Cordillera, and the spatial distribution of the inherited structures appears to control slip partitioning behavior of the Denali fault system across time scales ranging from 101 (historic seismicity) to 107 yr. The slip partitioning behavior of the Denali fault system highlights the mechanical importance of inherited structures leading to protracted shortening on splay thrust systems, which siphon slip from the master strike‐slip fault. We contend that the weakness of nearby reactivated terrane boundaries should be considered among other mechanisms commonly evoked to explain the partitioning behavior of continental strike‐slip fault systems (e.g., stress field rotation, obliquity angle, and strength of master strike‐slip fault).

show abstract

Section: Discussionsupporting

confidence: 92%

Suture Reactivation, Slip Partitioning, and a Protracted Strike‐Slip Rate Gradient in the Denali Fault System, Southern Alaska, USA

Waldien,

Roeske,

Chatterjee

et al. 2023

Tectonics

View full text Add to dashboard Cite

show abstract

“…The material similarity of the glacier's base and margins (Koehler & Carver, 2018) leads to a prescription of the linear friction law at the lateral boundary as well. Experimentation in Trantow (2014) suggests the lateral friction coefficient, β = β lat , is 5 times larger than the nearest basal sliding coefficient based on observed velocities and shear behavior near the margins.…”

Section: Numerical Modelmentioning

confidence: 99%

“…The locations of the reservoir areas, along with the basal water storage areas, are attributed to the characteristics of Bering Glacier's bedrock topography, shown in Figure 10a, whose shape is influenced by the local faults (Koehler & Carver, 2018; Trantow, 2020). In particular, it is the extension of the surrounding mountain ridges underneath the glacier, termed “subglacial ridges,” that are responsible for damming ice at these locations.…”

Section: The Quiescent Phasementioning

confidence: 99%

Evolution of a Surge Cycle of the Bering‐Bagley Glacier System From Observations and Numerical Modeling

Trantow,

Herzfeld

2024

JGR Earth Surface

View full text Add to dashboard Cite

The Bering‐Bagley Glacier System (BBGS), Alaska, Earth's largest temperate surging glacier, surged in 2008–2013. We use numerical modeling and satellite observations to investigate how surging in a large and complex glacier system differs from surging in smaller glaciers for which our current understanding of the surge phenomenon is based. With numerical simulations of a long quiescent phase and a short surge phase in the BBGS, we show that surging is more spatiotemporally complex in larger glaciers with multiple reservoir areas forming during quiescence which interact in a cascading manner when ice accelerates during the surge phase. For each phase, we analyze the simulated elevation‐change and ice‐velocity pattern, infer information on the evolving basal drainage system through hydropotential analysis, and supplement these findings with observational data such as CryoSat‐2 digital elevation maps. During the quiescent simulation, water drainage paths become increasingly lateral and hydropotential wells form indicating an expanding storage capacity of subglacial water. These results are attributed to local bedrock topography characterized by large subglacial ridges that dam the down‐glacier flow of ice and water. In the surge simulation, we model surge evolution through Bering Glacier's trunk by imposing a basal friction representation that mimics a propagating surge wave. As the surge progresses, drainage efficiency further degrades in the active surging‐zone from its already inefficient, end‐of‐quiescence state. Results from this study improve our knowledge of surging in large and complex systems which generalizes to glacial accelerations observed in outlet glaciers of Greenland, thus reducing uncertainty in modeling sea‐level rise.

show abstract

“…Examples include studies of: large earthquakes—modern (Crowell & Melgar, 2020; Liu et al., 2020; Xiao et al., 2021), historical (Boyd & Lerner‐Lam, 1988; Estabrook et al., 1992; J. M. Johnson et al., 1994), or paleoseismic (Carver & Plafker, 2008; Shennan et al., 2008); tsunamis—modern (Ye et al., 2021), historical (Freymueller et al., 2021; J. M. Johnson & Satake, 1995, 1997; D. J. Nicolsky et al., 2016), or paleotsunami (Nelson et al., 2015; R. C. Witter et al., 2014, 2016); active source studies of seismic structure (Barcheck et al., 2020; Bécel et al., 2015, 2017; J. Li et al., 2015, 2018; Shillington et al., 2015); geodetic observations of locking and coupling (Fletcher et al., 2001; Freymueller & Beavan, 1999; S. Li & Freymueller, 2018). Papers reviewing seismicity and tectonics of Alaska generally display these aftershock regions (Freymueller et al., 2008; Haeussler & Plafker, 2004; J. Johnson, 1998; Kirby et al., 2013; Koehler & Carver, 2018; Page et al., 1991; Ryan et al., 2012; Satake & Tanioka, 1999; R. Witter et al., 2019; Wyss & Wiemer, 1999). All of the studies above display at least two of the aftershock regions from Sykes et al.…”

Section: Introductionmentioning

confidence: 99%

“…Papers reviewing seismicity and tectonics of Alaska generally display these aftershock regions (Freymueller et al, 2008;Haeussler & Plafker, 2004;J. Johnson, 1998;Kirby et al, 2013;Koehler & Carver, 2018;Page et al, 1991;Ryan et al, 2012;Satake & Tanioka, 1999;R. Witter et al, 2019;Wyss & Wiemer, 1999).…”

mentioning

confidence: 99%

Aftershock Regions of Aleutian‐Alaska Megathrust Earthquakes, 1938–2021

Tape

Lomax²

2022

JGR Solid Earth

View full text Add to dashboard Cite

With five earthquakes (1938, 1946, 1957, 1964, and 1965), the Aleutian‐Alaska subduction plate boundary ruptured a length of 3,548 km. We revisit these five earthquakes—first studied in detail by Sykes (1971, https://doi.org/10.1029/JB076i032p08021)—through probabilistic relocation of carefully selected mainshocks and aftershocks. Our final catalog of 324 events is established from a set of 12 mainshocks that includes all Mw ≥ 7.7 megathrust earthquakes. Using the relocated catalog, we create revised aftershock regions delimited both parallel and normal to the trench. These aftershock regions exhibit significant differences from previous studies, with the following basic findings: the 10 November 1938 Mw 8.3 earthquake extended further west, to the Shumagin Islands, and further east, into the Kodiak region, relative to the prevailing aftershock region established by McCann et al. (1979, https://doi.org/10.1007/978-3-0348-6430-5_2). The 01 April 1946 Mw 8.6 sequence was anomalously concentrated near the trench, which implies near‐trench coseismic slip that contributed to the exceptionally large tsunami. The 09 March 1957 Mw 8.6 aftershocks spanned a 1,230 km length with numerous aftershocks within the outer‐rise region of the incoming Pacific plate. The 28 March 1964 Mw 9.2 aftershocks extended east into the Pamplona thrust system (south of Icy Bay, Alaska), suggesting coseismic rupture into this region; this is consistent with coseismic static displacements, as well as current estimates of interseismic locking. The post‐1965 events we examine are all smaller than the earlier events, but since they occurred in an era of improved data collection (seismic, geodetic, and tsunami), they provide a better opportunity for assessing the link between the distribution of aftershocks and the occurrence of coseismic, postseismic, and interseismic slip.

show abstract

Active faults and seismic hazards in Alaska

Cited by 21 publications

References 42 publications

Suture Reactivation, Slip Partitioning, and a Protracted Strike‐Slip Rate Gradient in the Denali Fault System, Southern Alaska, USA

Suture Reactivation, Slip Partitioning, and a Protracted Strike‐Slip Rate Gradient in the Denali Fault System, Southern Alaska, USA

Evolution of a Surge Cycle of the Bering‐Bagley Glacier System From Observations and Numerical Modeling

Aftershock Regions of Aleutian‐Alaska Megathrust Earthquakes, 1938–2021

Contact Info

Product

Resources

About