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Ralph A. Haugerud

Publications and source records attributed to Ralph A. Haugerud.

At least 19 recordsLinked to original sources
USGS2026

Deformed submarine terraces in Puget Sound, Pacific Northwest, indicate only one M >~7.5 earthquake on the Seattle fault zone in the past 11,000 yr

Submerged marine terraces in Puget Sound, deformed across the Seattle fault zone (SFZ), indicate that only one earthquake as large as M~7.5 has occurred in at least the past 11 kyr. Previous paleoseismic studies document a M~7.5 earthquake between 923–4 CE, which uplifted coastal marine terraces by as much as 8 m. We demonstrate that this earthquake was the only such event since ~11 ka by mapping and quantifying deformation of older marine terraces, now submerged in Puget Sound. The submerged terraces, attributed to a late-glacial sea-level lowstand, record both glacial isostatic rebound and tectonic deformation. Vertical offset of the ~11 ka terraces within the SFZ is comparable to that of the marine terraces uplifted in 923 CE, implying no additional large (M>~7.5) earthquake on the SFZ since ~11 ka. This result implies a longer recurrence interval than current hazard estimates, which assumes recurrence of M>7.1 events every 5 kyr. Our mapping of SFZ deformation since ~11 ka also supports fault segmentation and contiguous block uplift between the Seattle and Tacoma fault zones.

Washington↗
USGS2024

Geomorphic map of the Umatilla River corridor, Oregon

This map portrays the distribution of landforms along the Umatilla River in northeastern Oregon and covers a corridor 127 kilometers long from the confluence of the Umatilla River with the Columbia River upstream to Meacham Creek. The map encompasses the valley bottom and extends about 1 kilometer up the adjoining hillslopes. Map data are intended to support water quality and fisheries enhancement efforts pursuant to the First Foods, a resource-management approach that focuses on traditionally gathered foods including water, fish, big game, roots, and berries and calls attention to the reciprocity between people and the foods upon which humans depend. The Umatilla River drains about 6,300 square kilometers on the northwest slope of the Blue Mountains in northeast Oregon. Most of the drainage basin is underlain by Miocene basalt flows of the Columbia River Basalt Group. Younger, weakly lithified, late Miocene and early Pliocene gravel deposits of local origin (for example, McKay Formation) are mapped in a few places. Upland surfaces are mantled with windborne silt (loess) correlative with deposits elsewhere known as the Palouse Formation. Surfaces below an elevation of about 340 meters were inundated repeatedly by large Pleistocene glacial outburst floods, most emanating from glacial Lake Missoula in western Montana. In backflooded areas such as the lower Umatilla River valley, Missoula floods deposited extensive slack-water silt. Areas mapped as open water, active channel and tie channel, flood basin, valley bottom, and modified land constitute the geomorphic floodplain: the area subject to occasional inundation by the Umatilla River. Deposits and landforms within the floodplain are inset into Missoula flood deposits and hence postdate the 20–15-kilo-annum Missoula floods. Some floodplain deposits are no more than a few centuries old, as indicated by substantial erosion and deposition during the Umatilla River flood of February 2020, the largest since systematic measurements began in October 1903. Deposits and landforms of the floodplain are transient features within the longer-term incision of the Umatilla River into mid-Miocene flood basalts and younger gravel of the McKay Formation.

Oregon↗
USGS2022

The Chumstick Formation: Exploring the sedimentary and structural history

The Chumstick Formation (Gresens and others, 1981a,b) comprises Eocene (49 to ~45 Ma) fl uvial sandstone with lesser conglomerate, mudstone, and tuff currently exposed on the east fl ank of the North Cascade Range (fi g. 1). The unit is restricted to the northwest–southeast-trending region Willis (1953) called the Chiwaukum graben. To the northeast, Chumstick is separated from Swakane Biotite Gneiss and Napeequa Schist by the Entiat fault. To the southwest, the Leavenworth fault juxtaposes Chumstick strata with the 90 Ma Mount Stuart batholith, prebatholith rocks of the Chiwaukum Schist, and the Ingalls Tectonic Complex, and, farther south, ~61–51 Ma fl uvial strata of the Swauk Formation. Within the Chiwaukum graben lies a northwest-trending uplift of Swakane Biotite Gneiss termed the Eagle Creek anticline (Willis, 1953) or Eagle Creek fault zone (Evans, 1994).

Washington↗
USGS2021

When hazard avoidance is not an option: Lessons learned from monitoring the postdisaster Oso landslide, USA

On 22 March 2014, a massive, catastrophic landslide occurred near Oso, Washington, USA, sweeping more than 1 km across the adjacent valley flats and killing 43 people. For the following 5 weeks, hundreds of workers engaged in an exhaustive search, rescue, and recovery effort directly in the landslide runout path. These workers could not avoid the risks posed by additional large-scale slope collapses. In an effort to ensure worker safety, multiple agencies cooperated to swiftly deploy a monitoring and alerting system consisting of sensors, automated data processing and web-based display, along with defined communication protocols and clear calls to action for emergency management and search personnel. Guided by the principle that an accelerating landslide poses a greater threat than a steadily moving or stationary mass, the system was designed to detect ground motion and vibration using complementary monitoring techniques. Near real-time information was provided by continuous GPS, seismometers/geophones, and extensometers. This information was augmented by repeat-assessment techniques such as terrestrial and aerial laser scanning and time-lapse photography. Fortunately, no major additional landsliding occurred. However, we did detect small headscarp failures as well as slow movement of the remaining landslide mass with the monitoring system. This was an exceptional response situation and the lessons learned are applicable to other landslide disaster crises. They underscore the need for cogent landslide expertise and ready-to-deploy monitoring equipment, the value of using redundant monitoring techniques with distinct goals, the benefit of clearly defined communication protocols, and the importance of continued research into forecasting landslide behavior to allow timely warning.

Washington↗
USGS2020

Geologic map of the greater Portland metropolitan area and surrounding region, Oregon and Washington

The Portland-Vancouver-Hillsboro Metropolitan Area (metro area) has great scenic, natural, and cultural resources and is the major economic hub of Oregon. The metro area is subject to a variety of geologic hazards. Underthrusting of the oceanic plate along the Cascadia plate boundary fault, or megathrust, deforms the leading edge of North America and produces earthquakes on the megathrust and in the overlying plate. Rising magma from the deeper parts of the subduction zone produces active volcanoes that form the Cascades Arc, including Mount Hood and Mount St. Helens visible from Portland. Both volcanism and strong ground-shaking from earthquakes have impacted the metro area, most recently in the 1980 eruptions of Mount St. Helens and the 1993 magnitude (M) 5.7 Scotts Mills earthquake. Great offshore earthquakes as large as M 9 on the Cascadia megathrust have shaken the metro area every 500 years or so, most recently in 1700. Giant floods have inundated the metro area, from the ice age Missoula floods about 20,000 to 15,000 years ago to the flood generated by collapse of the Bridge of the Gods landslide dam on the Columbia River around 1421–1447 A.D. Geologic resources of the metro area include the southern part of the Mist Natural Gas Storage Field in the northwest corner of the map area, the Columbia South Shore Well Field aquifer in the Portland Basin, the Columbia River Basalt aquifer of the Tualatin Basin, and the Tualatin Basin Aquifer Storage and Recovery projects. The metro area includes several well-known American Viticultural Areas in the western part of the map area and numerous transportation, electrical transmission, and pipeline corridors. We created this map to provide a uniform, modern geologic database for the greater Portland metro area to better understand its tectonic setting, active faults, volcanoes, landslide hazards, and distribution of geologic materials and resources. Information in this database will be used to improve seismic hazard and resource assessments in this economically important region. NOTE: The sheet 1 map was divided into two parts—sheet 1 (north) and sheet 1 (south)—to facilitate printing and plotting the map.

Oregon, Washington↗
USGS2020

Geomorphic map of western Whatcom County, Washington

Western Whatcom County has a rich history of glaciation, sea-level change, fluvial erosion and deposition, landsliding, nearby volcanic activity, and human landscape modification. This lidar-derived geomorphic map interprets this history from the form and position of the Earth’s surface. The geomorphic record is broken into nine phases, beginning with the peak of the Vashon stade of the Fraser glaciation of Armstrong and others (1965) (phase 1), shortly after 16,000 years ago. The Cordilleran ice sheet was ≥1.6 km thick in the Bellingham area. Glacial lineations on high ground demonstrate that ice flow was from north to south. Storage of water in ice sheets at this time resulted in global sea level ~120 m lower than at present. The weight of the ice sheet depressed the land so that local relative sea level was at least 150 m higher than at present. As the ice sheet melted and thinned, it floated, broke up, and was replaced by salt water. The margin of the ice sheet—or at least its grounding line—retreated to the northeast of the map area during or before phase 2. Marine deposition, currents, and waves smoothed earlier-formed surfaces in the western part of the map area. Global sea level rose (because of melting of continental ice sheets), but the Fraser Lowland rose even faster (due to glacio-isostatic rebound following the loss of ice-sheet load), and thus local relative sea level fell. The Cordilleran ice sheet readvanced during the Sumas stade of Armstrong and others (1965). Oldest Sumas moraines formed when relative sea level at Bellingham was ~55 m (phase 3). Younger moraines formed when relative sea level at Bellingham was ~25 m (phase 4). The amount of Sumas ice retreat and readvance between these times is unknown. Younger Sumas events are marked by local moraines, progressive isostatic rebound and lowering of relative sea level, and changes in the flow of ice-marginal water. During phase 5, the southeast margin of the ice sheet advanced, perhaps because capture of ice-marginal drainage by the Samish River (east and south of the map area) meant the ice sheet was no longer trimmed by high-discharge flow along Squalicum channel. Farther west and north, the ice margin retreated between phases 4 and 5. Phases 6 through 9 may mark stillstands during further ice retreat. There were glacial outburst floods (jökulhlaups) during phases 7 and 8, and perhaps during phase 5. When Sumas ice left the area, perhaps about 11,500 years ago, the Nooksack River appears to have discharged northeast through Sumas Valley to the Fraser River. Details of the switch to its modern course are speculative, but archaeological and sediment-supply arguments suggest that the modern Nooksack River delta south of Ferndale formed within the past 5,000 years. The foothills of the North Cascades are decorated with abundant post-glacial deep-seated landslides. Anomalously high late Holocene beaches are found at Birch Bay, Neptune Beach, perhaps at Maple Beach on the east side of Point Roberts, and perhaps at the northwest corner of the Lummi Peninsula. These beaches may have been uplifted by earthquakes that did not rupture the surface. The low-relief landscape shaped by the Cordilleran ice sheet, along with fluvial infilling of low areas, resulted in abundant wetland, at least 70 percent of which has been diked and (or) drained to control flooding and facilitate farming.

Washington↗
USGS2020

Deglaciation of the Puget Lowland, Washington

Recently obtained radiocarbon ages from the southern Puget Lowland and reevaluation of limiting ages from the Olympic Peninsula in the light of new light detection and ranging (LiDAR) data suggest that the Juan de Fuca and Puget lobes of the Cordilleran ice sheet reached their maximum extents after 16,000 calibrated yr B.P. Source areas for both lobes fed through a common conduit, likely requiring that downstream responses to changes in either source area were similar. Dates for ice-sheet retreat are sparse and contradictory, but they suggest that retreat was rapid. Depositional and geomorphic evidence shows that retreat of the Juan de Fuca lobe predated retreat of the Puget lobe. No recessional end moraines have been identified in the Puget Lowland, in contrast to numerous recessional end moraines constructed by the Okanogan lobe east of the Cascade Range, and in contrast to later ice-sheet retreat in western Whatcom County north of the Puget Lowland. These observations lead to the hypothesis that collapse of the Juan de Fuca lobe, hastened by the instability of a marine-based ice sheet, steepened the ice-sheet surface over the eastern Strait of Juan de Fuca and diverted ice flow upstream of the Puget lobe to the west. Starved of ice, the Puget lobe retreated quickly.

Washington↗
USGS2018

New geologic mapping of the northwestern Willamette Valley, Oregon, and its American Viticultural Areas (AVAs)—A foundation for understanding their terroir

A geologic map of the greater Portland, Oregon, metropolitan area is planned that will document the region’s complex geology (currently in review: “Geologic map of the greater Portland metropolitan area and surrounding region, Oregon and Washington,” by Wells, R.E., Haugerud, R.A., Niem, A., Niem, W., Ma, L., Evarts, R., Madin, I., and others). The map, which is planned to be published as a U.S. Geological Survey Scientific Investigations Map, will consist of 51 7.5′ quadrangles covering more than 2,500 square miles, and it will represent more than 100 person-years of geologic mapping and studies. The region was mapped at the relatively detailed scale of 1:24,000 to improve understanding of its geology and its earthquake hazards. More than 100 geologic map units will record the 50-million-year history of volcanism, sedimentation, folding, and faulting above the Cascadia Subduction Zone. The geology contributes to the varied terroir of four American Viticultural Areas (AVAs) in the northwestern Willamette Valley: the Yamhill-Carlton, Dundee Hills, Chehalem Mountains, and Ribbon Ridge AVAs. Terroir is defined as the environmental conditions, especially climate and soils, that influence the quality and character of a region’s crops—in this case, grapes for wine. On this new poster (“New geologic mapping of the northwestern Willamette Valley, Oregon, and its American Viticultural Areas (AVAs)—A foundation for understanding their terroir”), we present the geologic map at a reduced scale (about 1:175,000) to show the general distribution of geologic map units, and we highlight, discuss, and illustrate six major geologic events that helped shape the region and form its terrior. We also discuss the geologic elements that contribute to the character of each of the four AVAs in the northwestern Willamette Valley.

Oregon↗
USGS2017

Geology of Seattle, a field trip

Seattle’s geologic record begins with Eocene deposition of fluvial arkosic sandstone and associated volcanic rocks of the Puget Group, perhaps during a time of regional strike-slip faulting, followed by late Eocene and Oligocene marine deposition of the Blakeley Formation in the Cascadia forearc. Older Quaternary deposits are locally exposed. Most of the city is underlain by up to 100 m of glacial drift deposited during the Vashon stade of Fraser glaciation, 18–15 cal k.y. B.P. Vashon Drift includes lacustrine clay and silt of the Lawton Clay, lacustrine and fluvial sand of the Esperance Sand, and concrete-like Vashon till. Mappable till is absent over much of the area of the Vashon Drift. Peak local ice thickness was 900 m. Isostatic response to this brief ice loading was significant. Upon deglaciation, global ice-equivalent sea level was about −100 m and local RSL (relative sea level) was 15–20 m, suggesting a total isostatic depression of ~115–120 m at Seattle. Subsequent rapid rebound outstripped global sea-level rise to result in a newly recognized marine low-stand shoreline at −50 m. The Seattle fault is a north-verging thrust or reverse fault with ~7.5 km of throw. Conglomeratic Miocene strata may record initiation of shortening. Field relations indicate that fault geometry has evolved through three phases. At present, the north-verging master fault is blind, whereas several surface-rupturing faults above the master fault are south verging. The 900–930 A.D. Restoration Point earthquake raised a 5 km × 35 km (or larger) area as much as 7 m. The marine low-stand shoreline is offset by a similar amount, thus there has been only one such earthquake in the last ~11 k.y. Geomorphology is largely glacial: an outwash plain decorated with ice-molded flutes and large, anastomosing tunnel valleys carved by water flowing beneath the ice sheet. Euro-Americans initially settled here because of landscape features formed by uplift in the Restoration Point earthquake. But steep slopes and tide flats were not conducive to commerce: starting in the 1890s and ending in the 1920s, extensive regrading removed hills, decreased slopes, and filled low areas. In steep slopes the glacial stratigraphy is prone to landslides when saturated by unusually wet winters. Seismic hazards comprise moderately large (M 7) earthquakes in the Benioff zone 50 km and more beneath the city, demi-millennial M 9 events on the subduction zone to the west, and infrequent local crustal earthquakes (M 7) that are likely to be devastating because of their proximity. Seismic shaking and consequent liquefaction are of particular concern in Pioneer Square, SoDo, and lower Duwamish neighborhoods, which are largely built on unengineered fill that was placed over estuarine mud. Debris from past Mount Rainier lahars has reached the lower Duwamish valley and a future large lahar could pose a sedimentation hazard.

Washington↗
USGS2014

Preliminary interpretation of pre-2014 landslide deposits in the vicinity of Oso, Washington

High-resolution topographic surveys allow fairly precise mapping of landslide deposits and their relative ages. Relative ages are determined by cross-cutting relations and the amount of smoothing—more smoothed slide deposits are older—of these deposits. The Tulalip Tribes, in partnership with the Puget Sound Lidar Consortium, acquired a high-resolution lidar (light detection and ranging) survey of the North Fork Stillaguamish River valley in 2013. This report presents a preliminary interpretation of the topography of this area using the lidar data at a scale of 1:24,000.

Washington↗
USGS2013

Lidar-revised geologic map of the Olalla 7.5' quadrangle, King, Kitsap, and Pierce Counties, Washington

The Olalla 7.5' quadrangle, which lies almost in the center of the Puget Lowland, displays the broad range of geologic environments typical of the region. The upland plain is fluted by the passage of the great continental ice sheet that last covered the area about 17,000 (14,000 radiocarbon) years ago. The plain is cut by channel deposits, both late glacial and postglacial in age, and it is cleaved even more deeply by one of the major arms of Puget Sound, Colvos Passage, which here separates the west coast of Vashon Island from the Kitsap Peninsula. Beneath the deposits of the last ice sheet is a complex sequence of older Quaternary-age sediments that extends about 400 m below the modern ground surface. These older sediments are best exposed along the shorelines and beach cliffs of Puget Sound, where wave action and landslides maintain relatively fresh exposures. The older sediments typically are compact, having been loaded by ice during one or more episodes of glaciation subsequent to their deposition. Locally these sediments are also cemented by iron and manganese oxides and hydroxides, a consequence of many tens or hundreds of thousands of years of weathering and groundwater movement. Our map is an interpretation of a 6-ft resolution lidar-derived digital elevation model combined with the geology depicted on the "Geologic map of the Olalla 7.5' quadrangle, King, Kitsap, and Pierce Counties, Washington," by Booth and Troost (2005), which was described, interpreted, and located on the 1953 1:24,000-scale topographic map of the Olalla 7.5-minute quadrangle. The original topographic base map, derived from 1951 aerial photographs, has 20-ft contours, nominal horizontal resolution of circa 40 ft (12 m), and nominal mean vertical accuracy of circa 13 ft (4 m). This new DEM has a horizontal resolution of 6 ft (2 m) and mean vertical accuracy circa 1 ft (0.3 m). The greater resolution and accuracy of the lidar DEM facilitated a much-improved interpretation of many aspects of the surficial geology, especially the distribution and relative age of landforms and the materials inferred to comprise them.

Washington↗
USGS2012

Holocene faulting in the Bellingham forearc basin: Upper-plate deformation at the northern end of the Cascadia subduction zone

The northern Cascadia forearc takes up most of the strain transmitted northward via the Oregon Coast block from the northward-migrating Sierra Nevada block. The north-south contractional strain in the forearc manifests in upper-plate faults active during the Holocene, the northern-most components of which are faults within the Bellingham Basin. The Bellingham Basin is the northern of four basins of the actively deforming northern Cascadia forearc. A set of Holocene faults, Drayton Harbor, Birch Bay, and Sandy Point faults, occur within the Bellingham Basin and can be traced from onshore to offshore using a combination of aeromagnetic lineaments, paleoseismic investigations and scarps identified using LiDAR imagery. With the recognition of such Holocene faults, the northernmost margin of the actively deforming Cascadia forearc extends 60 km north of the previously recognized limit of Holocene forearc deformation. Although to date no Holocene faults are recognized at the northern boundary of the Bellingham Basin, which is 15 km north of the international border, there is no compelling tectonic reason to expect that Holocene faults are limited to south of the international border.

Washington↗
USGS2011

Lidar-revised geologic map of the Uncas 7.5' quadrangle, Clallam and Jefferson Counties, Washington

In 2000 and 2001, the Puget Sound Lidar Consortium obtained 1 pulse/m 2 lidar data for about 65 percent of the Uncas 7.5' quadrangle. For a brief description of LIDAR (LIght Detection And Ranging) and this data acquisition program, see Haugerud and others (2003). This map combines geologic interpretation (mostly by Haugerud and Tabor) of the 6-ft (2-m) lidar-derived digital elevation model (DEM) with the geology depicted on the Preliminary Geologic Map of the Uncas 7.5' Quadrangle, Clallam and Jefferson Counties, Washington, by Peter J. Haeussler and others (1999). The Uncas quadrangle in the northeastern Olympic Peninsula covers the transition from the accreted terranes of the Olympic Mountains on the west to the Tertiary and Quaternary basin fills of the Puget Lowland to the east. Elevations in the map area range from sea level at Port Discovery to 4,116 ft (1,255 m) on the flank of the Olympic Mountains to the southwest. Previous geologic mapping within and marginal to the Uncas quadrangle includes reports by Cady and others (1972), Brown and others (1960), Tabor and Cady (1978a), Yount and Gower (1991), and Yount and others (1993). Paleontologic and stratigraphic investigations by University of Washington graduate students (Allison, 1959; Thoms, 1959; Sherman, 1960; Hamlin, 1962; Spencer, 1984) also encompass parts of the Uncas quadrangle. Haeussler and Wells mapped in February 1998, following preliminary mapping by Yount and Gower in 1976 and 1979. The description of surficial map units follows Yount and others (1993) and Booth and Waldron (2004). Bedrock map units are modified from Yount and Gower (1991) and Spencer (1984). We used the geologic time scale of Gradstein and others (2005). The Uncas quadrangle lies in the forearc of the Cascadia subduction zone, about 6.25 mi (10 km) east of the Cascadia accretionary complex exposed in the core of the Olympic Mountains (Tabor and Cady, 1978b). Underthrusting of the accretionary complex beneath the forearc uplifted and tilted eastward the Coast Range basalt basement and overlying marginal basin strata, which comprise most of the rocks of the Uncas quadrangle. The Eocene submarine and subaerial tholeiitic basalt of the Crescent Formation on the Olympic Peninsula is thought to be the exposed mafic basement of the Coast Range, which was considered by Snavely and others (1968) to be an oceanic terrane accreted to the margin in Eocene time. In this interpretation, the Coast Range basalt terrane may have originated as an oceanic plateau or by oblique marginal rifting, but its subsequent emplacement history was complex (Wells and others, 1984). Babcock and others (1992) and Haeussler and others (2003) favor the interpretation that the basalts were the product of an oceanic spreading center interacting with the continental margin. Regardless of their origin, onlapping strata in southern Oregon indicate that the Coast Range basalts were attached to North America by 50 Ma; but on southern Vancouver Island, where the terrane-bounding Leech River Fault is exposed, Brandon and Vance (1992) concluded that suturing to North America occurred in the broad interval between 42 and 24 Ma. After emplacement of the Coast Range basalt terrane, the Cascadia accretionary wedge developed by frontal accretion and underplating (Tabor and Cady, 1978b; Clowes and others, 1987). Domal uplift of the part of the accretionary complex beneath the Olympic Mountains occurred after ~18 Ma (Brandon and others, 1998). Continental and alpine glaciation during Quaternary time reshaped the uplifted rocks of the Olympic Mountains.

Washington↗
USGS2011

Geologic map of the Suquamish 7.5' quadrangle and part of the Seattle North 7.5' x 15' quadrangle, Kitsap County, Washington

The Suquamish 7.5' quadrangle is in the center of the Puget Lowland, Washington. The quadrangle contains the northern two-thirds of Bainbridge Island and adjacent parts of the Kitsap Peninsula. Puget Sound and contiguous waterways form 35 percent of the map area. Maximum elevation is 137 m in the northwest corner of the quadrangle, west of Suquamish; the modal elevation is 44 m. The center of the quadrangle is 20 km west-northwest of downtown Seattle. Winslow, in the southeast corner of the quadrangle, is a 35-minute ferry ride from Seattle. The Suquamish quadrangle lies within the Salish Lowland physiographic province (Haugerud, 2004), a broad region in the forearc of the Cascade Volcanic Arc that extends from south of Olympia, Washington, to north of Campbell River, British Columbia, and includes both the Puget Lowland of western Washington and the Georgia Depression of northwestern Washington and southwestern British Columbia. To the east are the Cascade Range and Coast Mountains; to the west is the outer-arc high of the Coast Ranges. The Salish Lowland is the locus of late Cenozoic subsidence: Jones (1996) indicates as much as 1 km of unconsolidated fill beneath some areas. The Lowland is crossed by east-west topographic highs formed by bedrock uplifts. A northern San Juan high divides the Lowland into Georgia Depression and Puget Lowland subprovinces. A southern high, which lies athwart the south end of Bainbridge Island immediately south of the map area, coincides with the Seattle Fault Zone along which uplift has brought Eocene rocks to elevations of 800-1,200 m, 8-10 km higher than equivalent strata in the floor of the Seattle structural basin that underlies central and northern Bainbridge Island and areas to the east (Brocher and others, 2001; Blakely and others, 2002). Deformation along the Seattle Fault appears to be driven by north-south shortening of the Cascade forearc (Wells and others, 1998). Pleistocene glacial deposits underlie most of the map area. Most extensive are the various members of the Vashon Drift, deposited in the Vashon stade of the Fraser Glaciation of Armstrong and others (1965) between about about 17,000 years ago. This study was undertaken in response to (1) awareness of the hazard posed by future earthquakes in the Seattle Fault Zone, at the south edge of the quadrangle, and the need to marshal geologic evidence for the rate and style of deformation; (2) increasing population on Bainbridge Island and consequent pressure on groundwater resources; (3) concern about landslide hazards; and (4) awareness of the role that the nearshore zone plays in supporting marine resources.

Washington↗
USGS2011

Lidar-revised geologic map of the Wildcat Lake 7.5' quadrangle, Kitsap and Mason Counties, Washington

This map is an interpretation of a 6-ft-resolution (2-m-resolution) lidar (light detection and ranging) digital elevation model combined with the geology depicted on the Geologic Map of the Wildcat Lake 7.5' quadrangle, Kitsap and Mason Counties, Washington (Haeussler and Clark, 2000). Haeussler and Clark described, interpreted, and located the geology on the 1:24,000-scale topographic map of the Wildcat Lake 7.5' quadrangle. This map, derived from 1951 aerial photographs, has 20-ft contours, nominal horizontal resolution of approximately 40 ft (12 m), and nominal mean vertical accuracy of approximately 10 ft (3 m). Similar to many geologic maps, much of the geology in the Haeussler and Clark (2000) map-especially the distribution of surficial deposits-was interpreted from landforms portrayed on the topographic map. In 2001, the Puget Sound lidar Consortium obtained a lidar-derived digital elevation model (DEM) for Kitsap Peninsula including all of the Wildcat Lake 7.5' quadrangle. This new DEM has a horizontal resolution of 6 ft (2 m) and a mean vertical accuracy of about 1 ft (0.3 m). The greater resolution and accuracy of the lidar DEM compared to topography constructed from air photo stereo models have much improved the interpretation of geology in this heavily vegetated landscape, especially the distribution and relative age of some surficial deposits. Many contacts of surficial deposits are adapted unmodified or slightly modified from Haugerud (2009).

Washington↗
USGS2010

Preliminary atlas of active shallow tectonic deformation in the Puget Lowland, Washington

This atlas presents an up-to-date map compilation of the geological and geophysical observations that underpin interpretations of active, surface-deforming faults in the Puget Lowland, Washington. Shallow lowland faults are mapped where observations of deformation from paleoseismic, seismic-reflection, and potential-field investigations converge. Together, results from these studies strengthen the identification and characterization of regional faults and show that as many as a dozen shallow faults have been active during the Holocene. The suite of maps presented in our atlas identifies sites that have evidence of deformation attributed to these shallow faults. For example, the paleoseismic-investigations map shows where coseismic surface rupture and deformation produced geomorphic scarps and deformed shorelines. Other maps compile results of seismic-reflection and potential-field studies that demonstrate evidence of deformation along suspected fault structures in the subsurface. Summary maps show the fault traces derived from, and draped over, the datasets presented in the preceding maps. Overall, the atlas provides map users with a visual overview of the observations and interpretations that support the existence of active, shallow faults beneath the densely populated Puget Lowland.

Open-File Report↗
USGS2009

Preliminary Geomorphic Map of the Kitsap Peninsula, Washington

The Kitsap Peninsula, in the center of the Puget Lowland of Washington State, has been glaciated repeatedly during the last 2 million years. This geologic history is significant to our understanding of crustal deformation, ground- and surface-water resources, the distribution of fishes, and other topics. Recent high-resolution lidar (LIght Detection And Ranging; also known as airborne laser swath mapping, or ALSM) topographic surveys of much of the Puget Lowland provide a more accurate depiction of the morphology of this forested landscape than has previously been available. More accurate morphology promises more accurate mapping of unconsolidated deposits and a more detailed earth history, particularly in this low-relief forested region where outcrops are not abundant and many deposits are similar in composition. In order to clarify the chain of observation and inference that proceeds from morphology to geologic map, this map describes the distribution of morphologic units - the 2-dimensional surfaces that bound near-surface deposits.

Open-File Report↗