Geology of the Prince William Sound and Kenai Peninsula region, Alaska: Including the Kenai, Seldovia, Blying Sound, Cordova, and Middleton Island 1:250,000-scale quadrangles

Wilson, Frederic H.; Hults, Chad P.

doi:10.3133/sim3110

Cited by 12 publications

(26 citation statements)

References 73 publications

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“…Damage from ground shaking was widespread, and the associated tsunamis inundated coastline infrastructure as far away as northern California. Local tsunamis damaged the Alaska (Wilson and Hults, 2012;Liberty et al, 2013;Haeussler et al, 2015). Faults that slipped during the 1964 Great Alaska earthquake include the Patton Bay fault (PBF), Hanning Bay fault (HBF), and Cape Cleare fault (CCF).…”

Section: The 1964 Great Alaska Earthquakementioning

confidence: 99%

“…We define the basal seismic unit IV as the Tertiary Orca Group of Moffit (1954), a unit that is exposed throughout much of the land around PWS (e.g., Wilson and Hults, 2012). We infer that these Tertiary rocks form the ocean-bottom surface where rugged seafloor topography prevails, and because of their hardness no sparker seismic signal penetration is obtained (e.g., Carlson and Molnia, 1978;Evans et al, 2000;Liberty et al, 2013).…”

Section: Pws Seismic Stratigraphymentioning

confidence: 99%

“…To identify and characterize active faults in the Orca Bay region, we use seismic data, multibeam bathymetry, published piston and gravity core measurements, and geologic mapping from adjacent islands (e.g., Wilson and Hults, 2012). We include four 10-to 20-km long, north-south seismic profiles that image several hundred meters beneath the seafloor (Fig.…”

Section: Orca Bay Active Faultsmentioning

confidence: 99%

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Landslides and Megathrust Splay Faults Captured by the Late Holocene Sediment Record of Eastern Prince William Sound, Alaska

Finn¹,

Liberty²,

Haeussler³

et al. 2015

Bulletin of the Seismological Society of America

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We present new marine seismic-reflection profiles and bathymetric maps to characterize Holocene depositional patterns, submarine landslides, and active faults beneath eastern and central Prince William Sound (PWS), Alaska, which is the eastern rupture patch of the 1964 M w 9.2 earthquake. We show evidence that submarine landslides, many of which are likely earthquake triggered, repeatedly released along the southern margin of Orca Bay in eastern PWS. We document motion on reverse faults during the 1964 Great Alaska earthquake and estimate late Holocene slip rates for these growth faults, which splay from the subduction zone megathrust. Regional bathymetric lineations help define the faults that extend 40-70 km in length, some of which show slip rates as great as 3:75 mm=yr. We infer that faults mapped below eastern PWS connect to faults mapped beneath central PWS and possibly onto the Alaska mainland via an en echelon style of faulting. Moderate (M w > 4) upper-plate earthquakes since 1964 give rise to the possibility that these faults may rupture independently to potentially generate M w 7-8 earthquakes, and that these earthquakes could damage local infrastructure from ground shaking. Submarine landslides, regardless of the source of initiation, could generate local tsunamis to produce large run-ups along nearby shorelines. In a more general sense, the PWS area shows that faults that splay from the underlying plate boundary present proximal, perhaps independent seismic sources within the accretionary prism, creating a broad zone of potential surface rupture that can extend inland 150 km or more from subduction zone trenches.

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Section: The 1964 Great Alaska Earthquakementioning

confidence: 99%

Section: Pws Seismic Stratigraphymentioning

confidence: 99%

Section: Orca Bay Active Faultsmentioning

confidence: 99%

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Landslides and Megathrust Splay Faults Captured by the Late Holocene Sediment Record of Eastern Prince William Sound, Alaska

Finn¹,

Liberty²,

Haeussler³

et al. 2015

Bulletin of the Seismological Society of America

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“…[28] The Contact fault system, of which the Bainbridge fault is a component, is comprised of faults that parallel the Alaska coastline west to Kodiak Island and east beneath PWS [e.g., Nelson et al, 1985;Dumoulin, 1987;Wilson and Hults, 2012]. The fault system roughly parallels the transition from uplift to subsidence during the 1964 earthquake (Figure 1) [e.g., Plafker et al, 1994].…”

Section: Bainbridge Fault and Contact Fault Systemmentioning

confidence: 99%

“…Although detailed bathymetry is not available within the Junken Trough, a 2004 multibeam survey that focused on the entrance to Bainbridge Passage shows a prominent, up-to-the-north, northeast-trending seafloor scarp near the northern limits of the Junken Trough profile (Figure 4). We interpret this growth fold to represent the along-strike expression of the Bainbridge fault, a fault that parallels and is possibly related to the Contact fault system (Figure 1) [Helwig and Emmet, 1981;Dumoulin, 1987;Bol and Gibbons, 1992;Wilson and Hults, 2012]. Along the Junken Trough profile, this fold is likely rooted in a fault at depth, and a large seafloor scarp suggests this fault may pose a significant tsunami or ground-shaking hazard to adjacent mainland communities and infrastructure, including Seward and other shallow waterways along the southern Kenai Peninsula [e.g., Plafker, 1969;Suleimani et al, 2011].…”

Section: Bainbridge Fault and Contact Fault Systemmentioning

confidence: 99%

Megathrust splay faults at the focus of the Prince William Sound asperity, Alaska

et al. 2013

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[1] High-resolution sparker and crustal-scale air gun seismic reflection data, coupled with repeat bathymetric surveys, document a region of repeated coseismic uplift on the portion of the Alaska subduction zone that ruptured in 1964. This area defines the western limit of Prince William Sound. Differencing of vintage and modern bathymetric surveys shows that the region of greatest uplift related to the 1964 Great Alaska earthquake was focused along a series of subparallel faults beneath Prince William Sound and the adjacent Gulf of Alaska shelf. Bathymetric differencing indicates that 12 m of coseismic uplift occurred along two faults that reached the seafloor as submarine terraces on the Cape Cleare bank southwest of Montague Island. Sparker seismic reflection data provide cumulative Holocene slip estimates as high as 9 mm/yr along a series of splay thrust faults within both the inner wedge and transition zone of the accretionary prism. Crustal seismic data show that these megathrust splay faults root separately into the subduction zone décollement. Splay fault divergence from this megathrust correlates with changes in midcrustal seismic velocity and magnetic susceptibility values, best explained by duplexing of the subducted Yakutat terrane rocks above Pacific plate rocks along the trailing edge of the Yakutat terrane. Although each splay fault is capable of independent motion, we conclude that the identified splay faults rupture in a similar pattern during successive megathrust earthquakes and that the region of greatest seismic coupling has remained consistent throughout the Holocene.

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Fluvial suspended sediment transfer and lacustrine sedimentation of recent flood turbidites in proglacial Eklutna Lake, western Chugach Mountains, Alaska

Schiefer

Geck

Ostman

et al. 2021

Hydrological Processes

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Suspended sediment delivery and deposition in proglacial lakes is generally sensitive to a wide range of hydrometeorologic and geomorphic controls. High discharge conditions are of particular importance in many glaciolacustrine records, with individual floods potentially recorded as distinctive turbidites. We used an extensive network of surface sediment cores and hydroclimatic monitoring data to analyse recent flood turbidites and associated sediment transfer controls over instrumental periods at Eklutna Lake, western Chugach Mountains, Alaska. Close to a decade of fluvial data from primary catchment tributaries show a dominating influence of discharge on sediment delivery, with various interconnections with other related hydroclimatic controls. Multivariate fluvial models highlight and help quantify some complexities in sediment transfer, including intra-annual variations, meteorological controls, and the influence of subcatchment glacierization. Sediments deposited in Eklutna Lake during the last half century are discontinuously varved and contain multiple distinctive turbidites. Over a 30-year period of stratigraphic calibration, we correlate the four thickest flood turbidites (1989, 1995, 2006, and 2012) to specific regional storms. The studied turbidites correlate with late-summer and early-autumn rainstorms with a magnitude of relatively instantaneous sedimentation 3-15 times greater than annual background accumulation. Our network of sediment core data captured the broad extent and sediment variability among the study turbidites and background sediment yield. Within-lake spatial modelling of deposition quantifies variable rates of downlake thinning and sediment focusing effects, and highlights especially large differences between the thickest flood turbidites and background sedimentation. This we primarily relate to strongly contrasting dispersion processes controlled by inflow current strength and turbidity. Sediment delivery is of interest for this catchment because of reservoir and water supply operations. Furthermore, although smaller floods may not be consistently represented, the lake likely contains a valuable proxy record of regional flooding proximal to major population centers of south-central Alaska including Anchorage.

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Geology of the Prince William Sound and Kenai Peninsula region, Alaska: Including the Kenai, Seldovia, Blying Sound, Cordova, and Middleton Island 1:250,000-scale quadrangles

Cited by 12 publications

References 73 publications

Landslides and Megathrust Splay Faults Captured by the Late Holocene Sediment Record of Eastern Prince William Sound, Alaska

Landslides and Megathrust Splay Faults Captured by the Late Holocene Sediment Record of Eastern Prince William Sound, Alaska

Megathrust splay faults at the focus of the Prince William Sound asperity, Alaska

Fluvial suspended sediment transfer and lacustrine sedimentation of recent flood turbidites in proglacial Eklutna Lake, western Chugach Mountains, Alaska

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