• Unangam Unikangis: Aleut stories of leadership and knowing

      Mack, Liza; Barnhardt, Ray; Carothers, Courtney; Chapin, F. Stuart III (2019-03)
      The central question of this dissertation is, "What do Aleut people know about the laws that directly affect their access to local resources?" The complex details of hunting and fishing regulations coupled with legislation that dictates access to natural resources will play a key role in Aleut leaders' ability to understand, disseminate, and protect these rights. Such policies include clauses that regulate who can and cannot participate based on blood quantum, which can be problematic for future generations of Aleut people as they marry and have children with people from outside the region. Further, with the abolishment of aboriginal title to lands and hunting and fishing rights in Alaska, understanding who owns the land and resources and how they are governed is imperative to Aleut people. This dissertation uses participant observation, critical case studies, key informant interviews, and a survey of Aleut leaders in the Eastern Aleutians to illustrate the ways in which Aleut people know and understand their environment and the ways they address natural resource management issues. It further demonstrates the way these issues are being addressed and learned about in two Eastern Aleutian communities. It also highlights the dynamic leadership of Aleut community members in the Eastern Aleutians. Some of the major findings include no reported change in subsistence use for respondents under the age of 50, a decline in the amount of subsistence used by older respondents, Aleut leaders spend years serving their communities in multiple capacities; and generally speaking, younger generations of public servants tend to become involved in community service as well.
    • Uncertainty in fish counting using an echo-counting technique as applied to data from a single-beam sonar

      Lai, Zhiguo (2002-08)
      A model of fish distribution in time and space and a single-beam sonar model are presented. Simulated sonar data are obtained and analyzed using the echo-counting method to determine the estimated number of fish. The results show that (1) when the fish rate is less than 1 fish/s, the error is within plus minus 15% and fish are overcounted more often than undercounted, (2) this method underestimates the number of fish by 57% of the actual number of fish for a fish rate of 5 fish/s, (3) fish counts are dominated by the noise if the threshold is lower than the noise level, (4) by varying the ping rate, the error could be as much as 72% for a fish rate of 10 fish/s and a ping rate of 10 pings/s, (5) by varying the pulse width, the error could be as much as 80% for a fish rate of 10 fish/s and a pulse width of 1.0 ms.
    • Uncertainty in fish location using a split beam sonar

      Ayers, Mark L. (2001-05)
      The enumeration of fish is of critical importance to the management of both commercial and sport fisheries in Alaska and worldwide. Current methods for riverine fish enumeration are inaccurate and unreliable. Improved fish counting accuracy in Alaskan rivers by acoustic methods is required. A split beam sonar system in the presence of noise is modeled. The sonar system including the received sonar pulse, receiver system, transducer beam pattern, propagation losses, and noise are modeled. An analysis of the effects of noise, pulse duration and sampling frequency on the uncertainty in fish location is presented. Signal to noise ratios less than 5 dB can cause significant errors in the calculation of received signal phase. A stationary fish with a signal to noise ratio of 15 dB has approximately plus-minus 0.001 degrees of uncertainty in the angles of arrival. Reducing the SNR to 3 dB the uncertainty increases to plus-minus 3.6 degrees in the angles of arrival.
    • Uncertainty quantification of gas production in the Barnett shale using time series analysis

      Joshi, Kishan Ghanshyambhai; Awoleke, Obadare; Hanks, Catherine; Ahmadi, Mohabbat (2015-12)
      Deterministic methods for evaluating uncertainty in production forecasts for unconventional shale plays are either unreliable or time intensive. This thesis presents an improved methodology for quantifying uncertainty in production forecasts using Logistic Growth Analysis (LGA) and time series modeling. The applicability of the proposed method is tested by history matching production data and providing uncertainty bounds for forecasts from eight Barnett Shale counties. The 80% confidence interval (CI) generated by this method successfully bracketed true production values for all the counties, even when approximately one-third of the data was used for history matching. In the methodology presented, the trend in the production data was determined using two different non-linear regression schemes. The predicted trends were subtracted from the actual production data to generate two sets of stationary residual time series. Time series analysis techniques (Auto Regressive Moving Average models) were thereafter used to model and forecast residuals. These residual forecasts were incorporated with trend forecasts to generate our final 80% CI. To check the reliability of the proposed method, I tested it on 100 gas wells with at least 100 months of available production data. The CIs generated covered true production 84% and 92% of the time when 40 and 60 months of production data were used for history matching, respectively. An auto-regressive model of lag 1 best fit the residual time series in each case. The proposed methodology is an efficient way to generate production forecasts and to reliably estimate uncertainty for short to medium time periods. It includes uncertainty due to parameter estimation using two different regression schemes. It also incorporates the uncertainty due to the variance of the residuals. The method is computationally inexpensive and easy to implement. The utility of the procedure presented is not limited to gas wells; it can be applied to any type of well or group of related wells.
    • Uncovering and enhancing motivation in a residential substance abuse treatment setting

      Morris, Alexandria V.; Renes, Susan; Gifford, Valerie; McMorrow, Samantha (2015)
      This project addresses how to enhance motivation in a residential substance abuse setting in order to encourage completion of treatment. This project discusses contingency management, music therapy, family therapy, and motivational interviewing and how they enhance motivation. Contingency management and music therapy were both found to be helpful in increasing motivation in residential settings. Family therapy was also found to increase motivation, but at smaller levels. Motivational interviewing, which is used by many therapists, also enhances motivation in a consumer and is considered an evidenced based practice. The project provides a motivational curriculum for use in a six-week residential treatment program. The curriculum incorporates all four areas found in the literature that can be used to enhance motivation and to uncover motivation and help to engage consumers in treatment.
    • Understanding institutional and social factors relating to the provisioning of water and sanitation services in rural Alaska: perspectives on community self-reliance from nine Native villages of Interior Alaska

      Ochante Cáceres, Mercedes Fátima (2013-05)
      The global community acknowledges the essential nature of potable water and proper sanitation to the realization of human rights. Since 1959 federal, state and tribal efforts have focused on the goal of equitably providing these services to Alaska Native villages. However, demographic and geographical realities along with limited resources pose formidable challenges to achieving this lofty goal. This thesis explores the challenges to providing safe drinking water in remote Interior Alaska villages and their impact on self-reliance from the perspectives of knowledgeable village residents. Findings from a grounded theory analysis reveal that despite competence and concerted efforts to meet community needs, social and institutional dimensions pose difficulties to sustainable water services. Such challenges include community perceptions about treated water, communication barriers, unharnessed local expertise and opportunities to develop local capacity, complicated needs assessment and resource acquisition processes, mismatched policies and technology vis-a-vis the realities of village living, and resident out migration.
    • Understanding Loglan.

      Rice, Stephen Leon (1994)
      Loglan is a language designed to help test Whorf's hypothesis that language shapes thought. Specifically, Loglan should encourage more creative and logical thought in its users. Such future users will need a readable textbook of the language; that is the purpose of the present work. <p>
    • Understanding place in fisheries management: an examination of ecological and social communities in the Pribilof Islands, Alaska

      Lyons, Courtney; Carothers, Courtney; Eckert, Ginny; Reedy, Katherine; Siddon, Christopher (2015-08)
      Holistic approaches toward fisheries management are widely considered a more sustainable option than standard single-species frameworks. This project uses the holistic frameworks of ecosystem-based fisheries management (EBFM) and place-making to examine the ecological and social systems of the Pribilof Islands and the ways in which fisheries management decisions have structured these systems. In Chapter 1, we sought to understand potential ecological constraints of temperature, fish predation, and interactions with a congener (red king crab; Paralithodes camtschaticus) on blue king crab (Paralithodes platypus) recovery. These examinations suggest that blue king crab juveniles switch strategies from predator avoidance to a strategy of predator deterrence in situations where predation is more likely. In addition, this research suggests that predatory interactions between crab congeners may be more likely than fish predation to inhibit blue king crab recovery. In Chapter 2, we sought to understand local place-making efforts and how they differed between the two Pribilof Island villages, as well as, how these place-making efforts articulated with development programs. We found that place-making efforts in both communities were based on maintaining residence in the islands and an appreciation of the wayof-life that residence provided. The way place-making efforts articulated with development programs, however, differed between the communities. In St. George, Alaska, residents selectively embraced development, only supporting initiatives that would help realize the goal of maintaining residence in the community, as opposed to integrating into a regional economy. Residents of St. Paul, Alaska, in contrast, had more autonomy and were able to control development projects in their community to support local place-making efforts. In Chapter 3 we used these data to develop a framework for assessing the vulnerability of fishing communities based on holistic, ethnographic understandings of local social systems. This framework showed St. George to be a highly vulnerable community, while St. Paul was only moderately vulnerable. These assessments challenged previously published, quantitative vulnerability assessments. The results of our investigations into the social and ecological systems of the Pribilof Islands support the idea that holistic perspectives provide important information that can drastically alter management understandings of both fish resources and the people who depend upon them.
    • Understanding reservoir engineering aspects of shale gas development on the Alaska North Slope

      Nyulund, Anna; Dandekar, Abhijit; Patil, Shirish; Ahmadi, Mohabbat (2015-12)
      Horizontal drilling and multi-stage hydraulic fracturing made it possible to develop US shale resources. Shublik shale is one of such US shale resources - it is one of the largest source rocks for hydrocarbon accumulations located on the Alaska North Slope. This study used the workflow introduced by Mirzaei and Cipolla in 2012 to investigate the effects of fracturing fluid flowback; shale porosity; matrix, fracture and unpropped zone permeability; hydraulic fracture spacing; permeability anisotropy; non-Darcy flow; gas adsorption/desorption using the complex-fracture-network model, referred to as an Unconventional Fracture Model (UFM), and Voronoi grid on well performance in the Shublik shale formation. In addition, the effects of natural fracture network orientation, fracture spacing and length were examined using a single porosity model with incorporated Discrete Fracture Network (DFN). The Schlumberger Mangrove Plug-In for Petrel platform was used to conduct the study. Mangrove has the DFN feature, which can be deactivated in the single porosity model. The results suggested that ignoring fracturing fluid flowback and non-Darcy effects can lead to overestimation of the gas recovery factor. Neglecting gas adsorption/desorption effects leads to underestimation of the gas recovery factor. In addition, smaller fracture spacing leads to a higher gas recovery factor. DFN orientation, fracture spacing and length affect the propped fracture area and should be incorporated into analysis from shale plays since it can result in either overestimation or underestimation of the gas recovery factor depending on fracture network propagation. Finally, examining multiple hydraulic fractures instead of one fracture is more accurate due to the stress shadowing effects and fracture network propagation.
    • Understanding reservoir engineering aspects of shale oil development on the Alaska North Slope

      Zanganeh, Behnam; Hanks, Catherine; Ahmadi, Mohabbat; Awoleke, Obadare (2014-05)
      Horizontal drilling and multi-stage hydraulic fracturing have made the commercial development of nano-darcy shale resources a success. The Shublik shale, a major source rock for hydrocarbon accumulations on the North Slope of Alaska, has huge potential for oil and gas production, with an estimated 463 million barrels of technically recoverable oil. This thesis presents a workflow for proper modeling of flow simulation in shale wells by incorporating results from hydraulic fracturing software into hydraulic fracture flow modeling. The proposed approach allows us to simulate fracture propagation and leak-off of fracturing fluid during hydraulic fracturing. This process honors the real proppant distribution, horizontal and vertical variable fracture conductivity, and presence of fracturing fluid in the fractures and surrounding matrix. Data from the Eagle Ford Shale in Texas was used for this modeling which is believed to be analogous to Alaska's Shublik shale. The performance of a single hydraulic fracture using a black oil model was simulated. Simulation results showed that for the hydraulically fractured zone, the oil recovery factor is 5.8% over thirty years of production, to an assumed economic rate of 200 STB/day. It was found that ignoring flowback overestimated oil recovery by about 17%. Assuming a constant permeability in the hydraulic fracture plane resulted in overestimation of oil recovery by almost 25%. The conductivity of the unpropped zone affected the recovery factor predictions by as much as 10%. For the case investigated, about 25% of the fracturing fluid was recovered during the first 2 months of production; in total, 44% of it was recovered over thirty years. Permeability anisotropy was found to have a significant effect on the results. These results suggest that assuming a constant conductivity for the fractures and ignoring the presence of water in the fractures and the surrounding matrix leads to overestimation of initial production rates and final recovery factors. In addition, the modified workflow developed here more accurately and seamlessly integrates the modeled induced fracture characteristics in the reservoir simulation of shale resource plays.
    • Understanding the lived experience of racist hate speech on American university campuses

      Matusitz, Jonathan Andre (2001-12)
      This research employs narrative methodology in order to understand the lived experience of students who have experienced racist racist hate speech on American university campuses. Thematic analysis of in-depth, conversational interview capta (Kvale, 1996) was used to find commonalities in co-researchers' experiences. The literature review includes a contextual and historical section on racism, and a detailed, standard definition of racist hate speech. Emergent themes from these narrative interviews were found in regard to victims' experiences of racist hate speech on American university campuses. Those themes are discussed in the order of the co-researchers' experience: (1) indignation and anger, (2) stereotyping, (3) ethnic resentment, and (4) ethnic superiority. The co-researchers' experiences illustrate that racist hate speech is not only talk, but can be experienced through other communicative actions.
    • Underwater bioacoustic analysis of bearded seal behavior off Barrow, Alaska

      Ajmi, Amal Romona; Castellini, Michael; Kelley, John; Murphy, Edward (1996-12)
      Bearded seal vocalizations were collected incidentally during the 1993 bowhead whale census. Analysis of seal locations, calculated by triangulation of the vocalizations, provided information on seal swim velocity, distribution, and movement. Swim speeds fell within previously documented values. Seal positions, when correlated with satellite images, suggested that seal distribution was directly associated with ice topography. Individually tracked seals exhibited different types of movements including: maintenance of position, rapid increase in speed and slower, prolonged directional travel. Swim speeds, distributions, and movements suggest distinct behaviors which may include foraging, territorial or female defense, or display. Movement and behaviors may alter as ice conditions change throughout the breeding season. Bioacoustics, when coupled with other research methods, is a useful tool in the study of the behavior of less accessible animals.
    • A unified viscoplastic model for the inelastic behavior of ice

      Dasari, Jeevana (2006-08)
      A physics-based SUVIC-I model is proposed for the ductile region of polycrystalline ice. It accounts for mixed hardening and directional softening using the three internal state variables - back stress, yield stress and drag stress. The main objective is to provide the best suitable material parameters for this model. The process to obtain these parameters is discussed in detail. The computational aspect of this model is implemented in the finite element program ABAQUS through a user subroutine UMAT for the axisymmetric and 3D models. The results are validated against the experimental data for constant strain rate and creep tests.
    • Uninhabited and free from work: an environmental and federal land-use policy history of Glacial Lake Atna wilderness, Alaska

      McLaughlin, Marley M.; Coen, Ross; Meek, Chanda; Ehrlander, Mary F. (2020-05)
      The Glacial Lake Atna area, a valley between the southern Alaska and Wrangell mountain ranges in Southcentral Alaska, despite its appearance today as remote, thickly forested, and seemingly "wild" in character, has a 10,000-year history of human habitation. The first peoples in Alaska made encampments and harvested subsistence resources on the shores of the glacial lake and its margins, while today residents and visitors to the region continue to inhabit, hunt, fish, gather berries, cut firewood, and generally subsist from the land in ways remarkably similar to their prehistoric forebears. Humans and nature have a long, shared history in the thirteen million-acre Glacial Lake Atna region, and yet, since the mid-1980s, amid the modern-day conservation movement to protect so-called wild places, the region has been bordered and patrolled in ways that separate humans from nature. Wilderness policies under the National Park Service and Bureau of Land Management suggest that wilderness areas are inherently pristine, devoid of human inhabitation, and without the imprint of human work. Alaska lands acts, most specifically the Alaska National Interest Lands Conservation Act of 1980, while allowing for subsistence, did not adequately address work and inhabitation. This thesis questions such policies and, through archaeological, historical, and policy analyses of humans and nature in the region, argues wilderness has never been truly uninhabited and free from work. The idea of "wilderness" lacks introspection as these areas contain quite a lot of human history, and indeed wilderness is a construct of romanticism and post-frontier ideologies.
    • United States Armed Forces' voluntary education program: The effect of enlisted service member retention

      Brauchle, Kenneth Charles; Smith, David M. (1997)
      The United States Armed Forces have sponsored off-duty voluntary higher education programs for fifty years. The investment in these programs by the Armed Services is substantial. In 1996, Department of Defense (DOD) expenditures for Tuition Assistance programs totaled $121 million. The longevity and scope of these military programs make them an ideal special case through which to study the outcomes of employer sponsored off-duty education. This study looked at the relationship between participation in military sponsored off-duty education programs and enlisted retention in the service. The data for the study was from a large (60,000 respondents) survey conducted by the DOD in 1992. Both univariate and multi-variate statistical analysis techniques were used. Additionally, over thirty semi-structured interviews were conducted with service members. The quantitative analysis supports the conclusion that long-term participation in off-duty education is significantly and positively related to intention to reenlist in simple bi-variate models. However, when several other variables thought to be related to retention are controlled the overall education participation effect is very small, accounting for little of the variation in intention to reenlist. A comparison of the education participation pattern in this data with previous studies leads to the conclusion that there has been a fundamental change in the relationship between off-duty education and retention in the last ten to fifteen years. The qualitative data suggest that the military places a high value on educational participation exhibited in formal and informal policies, the organizational reward system, promotions and attitudes. The opportunity to participate varies by location, specific job and military specialty. Servicemembers' attitudes toward education appear to evolve. Early participation seems to be extrinsically motivated with an intrinsic motivation developing as the servicemember continues to participate. The quantitative and qualitative data support the conclusion that the military has changed in its view of educational participation. The data point to the conclusion that the military has adopted educational participation as an integral part of the military culture. This value is so embedded within the environment that the effect of educational participation may be masked by other variables such as satisfaction with the military way of life.
    • Unsupervised multi-scale change detection from SAR imagery for monitoring natural and anthropogenic disasters

      Ajadi, Olaniyi A.; Meyer, Franz; Webley, Peter; Tape, Carl; Cahill, Catherine (2017-08)
      Radar remote sensing can play a critical role in operational monitoring of natural and anthropogenic disasters. Despite its all-weather capabilities, and its high performance in mapping, and monitoring of change, the application of radar remote sensing in operational monitoring activities has been limited. This has largely been due to: (1) the historically high costs associated with obtaining radar data; (2) slow data processing, and delivery procedures; and (3) the limited temporal sampling that was provided by spaceborne radar-based satellites. Recent advances in the capabilities of spaceborne Synthetic Aperture Radar (SAR) sensors have developed an environment that now allows for SAR to make significant contributions to disaster monitoring. New SAR processing strategies that can take full advantage of these new sensor capabilities are currently being developed. Hence, with this PhD dissertation, I aim to: (i) investigate unsupervised change detection techniques that can reliably extract signatures from time series of SAR images, and provide the necessary flexibility for application to a variety of natural, and anthropogenic hazard situations; (ii) investigate effective methods to reduce the effects of speckle and other noise on change detection performance; (iii) automate change detection algorithms using probabilistic Bayesian inferencing; and (iv) ensure that the developed technology is applicable to current, and future SAR sensors to maximize temporal sampling of a hazardous event. This is achieved by developing new algorithms that rely on image amplitude information only, the sole image parameter that is available for every single SAR acquisition. The motivation and implementation of the change detection concept are described in detail in Chapter 3. In the same chapter, I demonstrated the technique's performance using synthetic data as well as a real-data application to map wildfire progression. I applied Radiometric Terrain Correction (RTC) to the data to increase the sampling frequency, while the developed multiscaledriven approach reliably identified changes embedded in largely stationary background scenes. With this technique, I was able to identify the extent of burn scars with high accuracy. I further applied the application of the change detection technology to oil spill mapping. The analysis highlights that the approach described in Chapter 3 can be applied to this drastically different change detection problem with only little modification. While the core of the change detection technique remained unchanged, I made modifications to the pre-processing step to enable change detection from scenes of continuously varying background. I introduced the Lipschitz regularity (LR) transformation as a technique to normalize the typically dynamic ocean surface, facilitating high performance oil spill detection independent of environmental conditions during image acquisition. For instance, I showed that LR processing reduces the sensitivity of change detection performance to variations in surface winds, which is a known limitation in oil spill detection from SAR. Finally, I applied the change detection technique to aufeis flood mapping along the Sagavanirktok River. Due to the complex nature of aufeis flooded areas, I substituted the resolution-preserving speckle filter used in Chapter 3 with curvelet filters. In addition to validating the performance of the change detection results, I also provide evidence of the wealth of information that can be extracted about aufeis flooding events once a time series of change detection information was extracted from SAR imagery. A summary of the developed change detection techniques is conducted and suggested future work is presented in Chapter 6.
    • Up in smoke: exploring the relationship between forest firefighting and subsistence harvest

      Rodrigues, Alyssa V. S.; Little, Joseph; Greenberg, Joshua; Trainor, Sarah; Brinkman, Todd J. (2018-05)
      Wildland firefighting in Alaska is changing due to the impact of climate change on the boreal forest. Changes to the wildland firefighting regime could have significant impacts on community participation during fall subsistence hunting and, consequentially, food security levels. Many rural Alaska communities have mixed cash-subsistence economies in which people have to balance their time between earning an income and harvesting subsistence foods. Cash income is necessary to pay for things such as housing, electricity, gasoline, gun, ammunition, and other capital necessary to engage in subsistence. This dissertation aims to better understand the current relationship between Type 2, or hand crew, wildland firefighting and subsistence, primarily fall subsistence hunting, through several methods. Surveys and interviews were conducted with Type 2 wildland firefighters followed by policy recommendations. Econometric modeling of the wildfire attributes, community attributes, and firefighting wages and dispatches was conducted. Lastly, a food production simulation was conducted. Utilizing these various methods gives a well-rounded understanding of the relationship between firefighting and subsistence. Firefighting wages currently contribute to subsistence harvest productivity. As climate change lengthens the fire season, rural Type 2 fire crews will continue to participate in firefighting and fall subsistence hunting. Only under the most extreme estimates of future wildland fires does time spent fighting fire reduce time spent on subsistence fall hunting by much so that rural communities are unable to meet their subsistence needs.
    • Updating the art history curriculum: incorporating virtual and augmented reality technologies to improve interactivity and engagement

      Bender, Brook; Healy, Joanne; Via, Skip; Lott, Chris (2017-05)
      This project investigates how the art history curricula in higher education can borrow from and incorporate emerging technologies currently being used in art museums. Many art museums are using augmented reality and virtual reality technologies to transform their visitors' experiences into experiences that are interactive and engaging. Art museums have historically offered static visitor experiences, which have been mirrored in the study of art. This project explores the current state of the art history classroom in higher education, which is historically a teacher-centered learning environment and the learning effects of that environment. The project then looks at how art museums are creating visitor-centered learning environments; specifically looking at how they are using reality technologies (virtual and augmented) to transition into digitally interactive learning environments that support various learning theories. Lastly, the project examines the learning benefits of such tools to see what could (and should) be implemented into the art history curricula at the higher education level and provides a sample section of a curriculum demonstrating what that implementation could look like. Art and art history are a crucial part of our culture and being able to successfully engage with it and learn from it enables the spread of our culture through digital means and of digital culture.
    • Upper crustal structure of southern Alaska: An interpretation of seismic refraction data from the Trans-Alaska Crustal Transect

      Wolf, Lorraine W.; Stone, David B.; Davies, John N.; Harrison, William D.; Pulpan, Hans; Shapiro, Lewis H.; Wallace, Wesley K. (1989)
      Seismic refraction and wide-angle reflection data from the U.S. Geological Survey's Trans-Alaska Crustal Transect is used to investigate the upper crustal structure of southcentral Alaska. The data consist of two intersecting refraction lines: the 135-km Chugach profile which follows the E-W strike of the Chugach Mountains and the 126-km Cordova Peak profile which follows the N-S regional dip. The four shots of the Chugach profile and the five shots of the Cordova Peak profile were recorded on 120 portable seismic instruments spaced at 1-km intervals. Interpretation of data from the Chugach terrane indicates that near-surface unconsolidated sediment and glacial ice overlie rocks of unusually high average compressional velocities (5.4-6.9 km/s) in the upper 10 km of crust. A thick unit correlated with a metasedimentary and metavolcanic flysch sequence has velocities of 5.4-5.9 km/s. It is underlain by mafic to ultramafic metavolcanic rocks (6.0-6.4 km/s) correlated with the terrane basement. Mid-crustal layers beneath the Chugach terrane contain two velocity reversals (6.5 and 6.7 km/s) attributed to off-scraped oceanic sedimentary rocks which are underlain by mafic to ultramafic oceanic volcanic crust (7.0-7.2 km/s). Interpretation of data from the Prince William terrane indicates systematically lower velocities in Prince William terrane rocks as compared to Chugach terrane rocks at comparable depths. The upper 10 km of crust, having average compressional velocities of 3.0-6.2 km/s, is correlated with clastic sedimentary and volcanic rocks which are overlain by younger terrigenous sedimentary rocks. A 2-km thick layer at 10-12 km depth is correlated with mafic to ultramafic Prince William terrane basement rocks. The difference in velocity structure between the Chugach and Prince William terranes suggests that the Contact fault zone is a terrane boundary which extends to a depth of at least 10-12 km. Deep structure beneath the two terranes is not well constrained by the seismic refraction data. Potential field data support the interpretation that a thick low-velocity zone occurs at a 12-15 km depth and may contain subducted continental rocks of the Yakutat terrane, which is currently accreting to and being thrust beneath the North American continent along the Gulf of Alaska margin.