Search for: All records

Abstract Sediment thermal history controls the progress of diagenetic reactions that can alter the mechanical behavior of material entering a subduction zone that then: accretes to the margin, hosts the plate boundary interface, or is carried deeper within the Earth. On the Cascadia margin offshore Oregon (USA), hydrothermal circulation in the oceanic crust affects thermally controlled processes, enhancing sediment alteration above the MARGIN seamount, which is buried by the Astoria Fan. Hydrothermal circulation increases temperatures at the summit of the seamount and in the overlying sediment by up to ∼100°C. We use sediment thermal history constrained by heat flux observations to model the expected progress of the smectite‐to‐illite reaction around the MARGIN seamount. Above the seamount, the smectite‐to‐illite reaction is expected to progress to completion ∼250 m below the seafloor; away from the seamount, smectite is likely unaltered to a burial depth of ∼800 m. The altered sediment above the seamount has higher rigidity and p‐wave velocity than the surrounding sediment. Spatial variability in sediment alteration may be present around other buried seamounts. We use vertical gravity gradient anomalies to estimate the locations and heights of additional seamounts. Each of these seamounts may have altered sediment around it, which could affect deformation and seismicity in the margin wedge. Because cemented sediment with greater elastic strength is better able to store elastic strain energy, enhanced sediment alteration and cementation above seamounts entering the subduction zone could facilitate earthquake nucleation for material in the margin wedge that was above a seamount prior to subduction. 

Abstract Temporal changes in seismic velocity estimated from ambient seismic noise can be utilized to infer subsurface properties at volcanic systems. In this study, we process 7 years of continuous seismic noise at Axial Seamount and use cross‐correlation functions to calculate the relative seismic velocity changes (dv/v) beneath the caldera. We find a long‐term trend of decreasing velocity during rapid inflation, followed by slight increase in velocities as background seismicity increases and inflation rate decreases. Furthermore, we observe small short‐term increases indv/vwhich coincide with short‐term deflation events. Our observations of changes indv/vand their correlation with other geophysical data provide insights into how the top ∼1 km of the crust at Axial Seamount changes in response to subsurface magma movement and capture the transition from a period of rapid reinflation to a period where the caldera wall faults become critically stressed and must rupture to accommodate further inflation. 

ABSTRACT The cost of basic drinking water services has implications for affordability, investment capacity, and public health. The fragmentation of drinking water services in the United States makes it difficult to reliably track and compare what customers pay for basic drinking water services. This paper uses a new, national dataset to examine the social, political, environmental, and institutional drivers of the cost of basic drinking water services, measured as the cost to households of 6000 gal of water per month. We find basic drinking water service costs vary widely across the United States. Costs are generally higher in smaller and more liberal cities and lower in places that rely on groundwater sources. Our findings provide a unique national perspective on variation in, and drivers of, the cost of basic water services and can inform efforts to improve the affordability, accessibility, and quality of drinking water services in the United States. 

The origin of rupture segmentation along subduction zone megathrusts and linkages to the structural evolution of the subduction zone are poorly understood. Here, regional-scale seismic imaging of the Cascadia margin is used to characterize the megathrust spanning ~900 km from Vancouver Island to the California border, across the seismogenic zone to a few tens of kilometers from the coast. Discrete domains in lower plate geometry and sediment underthrusting are identified, not evident in prior regional plate models, which align with changes in lithology and structure of the upper plate and interpreted paleo-rupture patches. Strike-slip faults in the lower plate associated with oblique subduction mark boundaries between regions of distinct lower plate geometry. Their formation may be linked to changes in upper plate structure across long-lived upper plate faults. The Juan de Fuca plate is fragmenting within the seismogenic zone at Cascadia as the young plate bends beneath the heterogeneous upper plate resulting in structural domains that coincide with paleo-rupture segmentation. 

This research paper analyzes the emotions that students experience while completing ill-defined complex problems called Open-Ended Modeling Problems in their engineering courses. Students are asked to make their own modeling decisions, rather than being given those assumptions, as is the case in most textbook problems. There are many approaches they can take, and having to make decisions and assumptions that impact the problem has been found to generate strong emotions. Goldin’s research on mathematics education asserts that students tend toward affective pathways while completing problems. An affective pathway is the sequence of emotions that a student goes through while solving a problem. Goldin theorizes that there are two main categories of affective pathways that students fall into: positive pathways and negative pathways. This paper builds on our previous work on the development of a survey instrument to quantitatively measure affective pathways. The survey asked students to drag and drop emotions into the order they experienced them during their problem solving process. In this study, we sought to improve upon our survey instrument. Based on our previous research, we added several emotions and alphabetized the list to see whether the order of words impacted the responses. Here, we examine the results from an updated survey question as well as a small set of interviews conducted to investigate how students approach answering the survey question by having them think aloud while completing it. The survey was sent to six classes at five universities, and interviews were conducted with six students at two of those universities. Through our analysis, we found that most students feel confused or frustrated at some stage, and that their emotions change as they continue from start to finish, which is in line with the findings of the previous version of the survey instrument. We are looking further into whether the students turned their frustrations into the positive or negative pathways that Goldin describes. From the interviews, we found most of the verbalized pathways matched what was submitted through the survey instrument. However, there were instances where the submitted and verbalized pathway did not match, suggesting further changes to the question’s implementation. Developing a reliable method for measuring affective pathways will enable future study of why and when positive or negative pathways occur, as well as potential actions that engineering educators can take to help students interrupt negative pathways. Goldin’s work suggests that negative pathways influence students’ global affect, which could impact retention in engineering. 

Sea urchins have become significant mariculture species globally, and also serve as invertebrate model organisms in developmental biology. Cis-regulatory elements (enhancers) control development and physiology by regulating gene expression. Mutations that affect the function of these sequences may contribute to phenotypic diversity. Cis-regulatory targets offer new breeding potential for the future. Here, we use the CRISPR/Cas9 system to disrupt an enhancer of Endo16 in developing Lytechinus variegatus embryos, in consideration of the thorough research on Endo16’s regulatory region. We designed six gRNAs against Endo16 Module A (the most proximal region of regulatory sequences, which activates transcription in the vegetal plate and archenteron, specifically) and discovered that Endo16 Module A-disrupted embryos failed to undergo gastrulation at 20 h post fertilization. This result partly phenocopies morpholino knockdowns of Endo16. Moreover, we conducted qPCR and clone sequencing experiments to verify these results. Although mutations were not found regularly from sequencing affected individuals, we discuss some potential causes. In conclusion, our study provides a feasible and informative method for studying the function of cis-regulatory elements in sea urchins, and contributes to echinoderm precision breeding technology innovation and aquaculture industry development. 

What are people’s expectations of interracial political coalitions? This research reveals expectations of flexible interracial coalitions stemming from how policies and racial groups are viewed in terms of perceived status and foreignness. For policies seen as changing societal status (e.g., welfare), people expected Black–Hispanic political coalitions and viewed Asian Americans as more likely to align with Whites than with other minorities. For policies seen as impacting American identity (e.g., immigration), people expected Asian–Hispanic coalitions and that Black Americans would align with Whites more than other minorities. Manipulating a novel group’s alleged status and cultural assimilation influenced coalitional expectations, providing evidence of causality. These expectations appear to better reflect stereotypes than groups’ actual average policy attitudes and voting behavior. Yet these beliefs may have implications for a diversifying electorate as White Americans strategically amplified the political voice of a racial group expected to agree with their personal preferences on stereotyped policies.