Meghan Miller - US grants

The Alboran Sea was created in the wake of the young subduction zones that swept across the Western Mediterranean in the Neogene during the convergence of Africa and Europe. The Gibraltar Arc and Alboran Sea are the westernmost part of the system and one of the most confusing. The mixture of westward rollback, extension, strike-slip, volcanism, uplift and subsidence has defied attempts to compose a consistent scenario that explains all of the obervations. Partly as a result of inadequate data, there are many models that have been proposed involving subduction, slab breakoff, delamination and drips. There is credible evidence that the lithospheric mantle of the overriding plate of a west-facing subduction zone has been thinned by both back-arc stretching and some type of convective removal (e.g. drips, delamination, etc.). The process of convective thinning is poorly understood but is believed to be important in driving uplift and subsidence of the Earth?s surface, influencing rates of deformation in active orogens, and contributing to recycling of continental materials back into the mantle.

This award provides for a multidisciplinary, international investigation of the Alboran Sea, Gibraltar arc, Atlas Mountains and surrounding areas in the western Mediterranean using passive and active seismology, magnetotellurics, geochemistry, petrology/structural geology, and geodynamic modeling. The overall goal of the project is to study the processes responsible for convective thinning in the Gibraltar-Alboran Sea region. The project, known as PICASSO, has now been funded in Spain and Ireland as a colloaborative EU-US program, with proposals from a number of other EU nations submitted or in process. The project was selected as the pilot experiment for TopoEurope, an EarthScope-like initiative recently approved by the European Science Foundation. A large part of the field deployments will be done by European scientists, including a 3D EarthScope-type rolling array (IberArray), with additional targeted field experiments by US investigators. The IberArray is already underway with ~60 stations deployed in the PICASSO field area.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

During the Cenozoic, southwestern North America underwent a shift from Farallon subduction to the present Pacific - North American strike-slip plate boundary, the San Andreas fault system (SAF). As a result, much of the southwestern U.S. experienced extension, in part the result of orogenic collapse prior to and during the transition from convergence to the current transform boundary. Yet deformation and volcanism still occur at great distances from the plate boundary, through the Basin and Range, around the edges of the Colorado Plateau, and in the Rocky Mountains. The structure of the continental lithosphere is linked to structures deeper in the upper mantle beneath each of tectonic provinces, and the details of the lithosphere and deeper structure and the overall response to the change in tectonic regime are not clearly understood. As the USArray Transportable Array rolls across the continent, it is uniformly covering the Western U.S., recording teleseismic earthquakes. These data, plus data integrated from the LA RISTRA, Deep Probe, and CD-ROM experiments in addition to data from the COARSE array in Arizona, will provide a wealth of information on the lithosphere and upper mantle structure. These models will be constrained by previous active source and petrologic data. This project is examining, in 3D, the Earth's discontinuity structure from the crust thru the 660 km discontinuity to systematically look for important tectonic/geodynamic indicators: sources of isostatic support, regions of thermal disequilibrium, partial melt, and rheological heterogeneity, slab fragments and slab interactions with the transition zone. The resulting images will be used to interpret the 4D tectonic and geodynamic evolution of the Colorado Plateau in relation to the evolution of its surrounding tectonic provinces: southern Basin and Range, southern Rocky Mountains, and the Rio Grande Rift.

The research uses a combination of surface wave tomography and P- and S-wave receiver functions to clearly image the base of the crust, the lithosphere-asthenosphere boundary (LAB), and the upper mantle structure through the transition zone beneath the Four Corners area of the southwestern U.S. USArray Transportable Array teleseismic data combined with previous broadband array studies have been used to make common conversion point (CCP) stacked PdS and SdP receiver function and surface wave tomography image volumes. The receiver functions have been made with two types of scattered waves: P converted to S (PdS), and S converted to P (SdP). The use of both PdS and SdP allows for independent models of the same area, and provides different frequency bands of investigation and different raypaths to image lithospheric and upper mantle structure. Since receiver functions and surface wave dispersion have different sensitivities to velocity structure jointly inverting the receiver functions and the shear velocity values provides independent estimates of structure. A receiver function images velocity-density discontinuities, not the absolute velocity structure. It senses the high frequency velocity fluctuations, and in some cases density fluctuations in the vertical direction. Phase velocities of surface waves, on the other hand, are most sensitive to the absolute shear velocity structure. In principle the two can be inverted jointly to overcome the non-uniqueness of the receiver-function inversion and the lower vertical resolution of surface-wave tomography.

Mapping 3D variations in the Moho, the LAB, and the transition zone discontinuities with multiple methods will provide a consistent framework for interpreting 4D Cenozoic extension, compression, and local convection features (upwellings, decompression melts, and mantle drips) beneath the southwestern U.S. Results of this study will be useful to non-seismologists interested in continental evolution, extensional dynamics, geodynamics, volcanology, and structural geology, both in the western U.S. and elsewhere. The methodology will be applicable to other regional array data, including future USArray data. Two graduate students will be trained in the use of seismic array data and integrated geophysical interpretation.

In addition to the research objectives of this project, the award will support a new investigator at the University of Southern California and the education and training of two graduate students.

Technical merit

This project is the organization and teaching of a five-day short course for graduate students and other early career scientists on the opportunities and challenges in the processing and analysis of much increased volumes of time series data. The primary goal is to inspire a new set of leaders who are more able to exploit the large volumes of data coming from the NSF's EarthScope program. The emphasis of the short course is on seismic data from USArray. The short course is held at Northwestern University in August of 2010 and builds upon and draws from an earlier short course on these themes, which was held in the summer of 2009. The PIs are designing and delivering the program in collaboration with USArray and IRIS and a small number of guest instructors. The course takes place in a computer laboratory in the main library of Northwestern University. The curriculum includes lectures followed by hands-on exercises, and finishes with student group projects carried out during the five days.

Broader Impacts

This project directly addresses issues of human infrastructure through workforce development. The top short-term goal of this project is training of the next generation of seismologists in 1) the use of the best current generation data analysis tools and 2) feeling empowered to further develop the tools currently available to the seismological community. This project represents a community-based approach to specialized educational content. We intend to collect and share the student projects through a student-designed and -maintained wiki. Course materials will be also organized and posted to the web in collaboration with the Education and Outreach Program of the Incorporated Research Institutions or Seismology.

One of the intriguing features of plate tectonics is that many active and ancient subduction zones have a pronounced arc-shaped morphology, with their topographic expressions stretching over hundreds to thousands of kilometers in length. Studying subduction, in general, is essential to understanding the evolution of the planet. More fully understanding the structure and dynamics of lithosphere, the relatively rigid outer shell of the Earth, subducting along highly arcuate plate boundaries will aid in constraining geologically recorded tectonic events, global plate motions, plate boundary deformation, and the role of subducted oceanic lithosphere in mantle convection. The overarching research goal of this CAREER award is development of an improved understanding of the structural and morphological evolution of arcuate shaped convergent margins through the study of four active arcs: the Mariana, Antilles, Betic-Rif, and Banda arcs, using a range of tools, including seismological imaging and geodynamic modeling. The expected findings will provide an important contribution to basic research on plate tectonics, an improved understanding of the structure and evolution of the tectonic plate boundaries, and the nature of seismicity in these regions. The educational goal is to train and prepare undergraduate graduate students as the next generation of geoscientists who are able to understand and effectively utilize both geophysical and geological data from subduction zones.

This CAREER award will investigate, in detail, the origin and evolution of the deep Earth structure of four target arcs. Improved imaging and modeling of these arcs will provide a way to test geodynamic hypotheses, for example, that curved subduction zones have evolved into their current configuration due to interactions of cold, dense oceanic lithosphere with positively buoyant features, such as oceanic plateaus or continental lithosphere, resulting in curved morphology as a result of trench rollback and slab fragmentation. Each of the four arc systems, have different length scales and topographic expressions, unique individual tectonic histories and plate configurations, yet they all exhibit highly arcuate convergent boundary structures and are bounded by buoyant crustal and lithospheric bodies at their cusps. This project proposes to examine these similarities and differences in order to better understand the geodynamic evolution and mantle structure at tightly curved convergent boundaries in terms of rollback, mantle flow, and the influence of buoyant "pinning" features at the ends of the arcs. This award will also fund development of an integrated education and research program based on understanding of seismicity, volcanism, mantle convection, plate tectonics, and geologic processes from both field and classroom based learning. The field component of the new Tectonophysics course will include deployment and collection of broadband seismic data along the several of the Antilles Islands and in northern Morocco, plus regional geologic mapping and sampling along portions of the active arcs. Both undergraduates and graduate students will participate in the course and other teaching modules developed through this award and will be part of USC's Problems Without Passports program that combine inquiry-based learning exercises with research in a foreign country.

Eastern Indonesia is one of the least well-understood geological domains of our planet, and yet the region provides a truly remarkable natural experiment for unraveling some of the major puzzles of plate tectonics. The recent collision of the Australian continent with the active volcanic arc in the Banda region effectively captures the initiation of continental mountain building and the cessation of island arc volcanism, offering a rare glimpse into a set of processes that have shaped Earth's evolution over geologic time. Since oceanic subduction and subsequent continental collision have occurred in different stages along the Banda arc, we plan to use the region to study and assess the spatio-temporal evolution of this transition. This work will help fill fundamental gaps in general understanding of collisional tectonics and formulate answers to outstanding questions about the interrelationships between the history of convergence and the present-day crustal, lithospheric and mantle structure, and the way this relates to topography. This study of the Banda arc holds promise for clarifying the relationships between surface uplift, crustal deformation and recycling, lithospheric structure, subduction, and mantle convection.

We have assembled an international multidisciplinary research team to constrain a sophisticated dynamical model of regional collision and subduction using passive seismology, topographic analysis, targeted geochronology, and a collaboratively led geodetic campaign. The research group includes scientists from Indonesia, Australia, Germany, the Netherlands, Portugal, and the U.S., and an important outcome will be to strengthen and catalyze future scientific collaboration between these countries. The award is co-funded by the NSF Geophysics and Tectonics Programs, and the Office of International Science and Engineering (OISE). All results, data, and newly developed methods will be shared freely online, benefiting future similar imaging or tectonic modeling efforts.

With the advent of EarthScope's USArray and other dense seismic arrays, there is an unprecedented opportunity for investigating the seismic structures within the deep Earth, all the way to the core. Detecting structures in the very deepest part of the Earth provide essential constraints in understanding many aspects of the chemical and thermal history of the planet. This grant will fund further development of array imaging techniques that will allow for more detailed investigation of how and why there are such complex structures at this great depth and how they link to the evolution of the Earth. The grant will provide support for a postdoc, a graduate student, and foster continued international collaborations in Europe.

Observations of seismic phases sampling the lower mantle have suggested Ultra Low Velocity Zones (ULVZs), a possible perovskite to postperovskite related D" layer, Large Low Shear Velocity Provinces (LLSVPs), and rolling-hills of primordial material on the core-mantle boundary (CMB). Considerable progress has been made toward developing dynamical and mineralogical based mantle models compatible with seismic observations at the deep mantle, yet many details are still missing. It is still uncertain whether the densities and velocities of ULVZs are related to possible partial melting or have a distinct chemical origin, but the information about physical properties needed to answer this question are poorly constrained. For example the major phase used in imaging ULVZs, SPdKS, is not particularly sensitive to density and the velocities have strong trade-off with the shape of the structures. Other seismic observations have shown connections between the geographic distribution of the observed D? layer: where the post-perovskite layer is thickest beneath fast regions and disappears beneath slow regions. However, it is difficult to distinguish the velocity gradient effects caused subducted oceanic lithosphere at the base of the mantle from phase boundary effects. The data set from USArray and other arrays, especially the greater PICASSO (partially funded by NSF-CD and CAREER) array, display waveform complexity at all ranges with remarkable coverage. This grant will provide funding to better constrain mantle structures and answer questions such as: (1) Can we resolve and distinguish between the trade-off of different elastic properties? (2) Can we determine the 3D geometry of the ULVZ's? (3) Are there other types of low velocity zones besides ULVZs existing at CMB? (4) How compatible are the inferred slab histories with the presence of lower mantle structures? (5) What is the relationship between D? and slabs in the deep mantle? (5) How well can we resolve the edges of the LLSVPs? To answer those questions, we will use array seismology techniques, waveform modeling and the newly developed Multi-Pathing Detector (MPD) to sharpen current tomographic models and produce synthetic seismograms that match observed waveforms complexities. The physical dimensions of these structures in the lower mantle and their inferred seismic parameters will be used in geodynamic models of mantle convection and explored in mineral physics experiments at CMB conditions. These further mineral physics and geodynamic experiments will allow for improvement in our understanding of the connection between subducted slabs, the D? layer, ULVZs, and LLSVPs and the dynamic evolution in the deep mantle.

? DESCRIPTION (provided by applicant): The overarching goals of the proposed project are to identify shared and distinct early behavioral indicators for autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) symptoms, and to better understand early developmental pathways to ASD and ADHD in children at risk for each syndrome. ASD and ADHD are two prevalent disorders emerging early in childhood, each conferring significant long-term impairment. Co-occurrence is common, and there is evidence of shared heritability and familial transmission, as well as overlapping neural and neurocognitive abnormalities, but little i known about unique and shared features very early in development, prior to diagnosis. It is clear that determining early signs uniquely associated with the development of ASD or ADHD is critical to enhancing accurate early detection efforts and identifying ideal targets and time point for intervention. What has been less well appreciated is that the impact of prevention and early intervention efforts will also be heightened by identifying transdiagnostic factors, or processes shared across disorders, that underlie symptom development. This is an ideal approach to apply to the study of ASD and ADHD because, given evidence of shared biological and behavioral abnormalities, it is likely that some early behavioral indicators also overlap, serving as general indices of atypical development that could be leveraged for transdiagnostic treatment development and prevention efforts. Two longitudinal studies are proposed to examine early behavioral indicators and developmental trajectories in three groups of children: infant siblings of children with ASD (high-risk ASD), infant siblings of children with ADHD (high-risk ADHD), and infant siblings of typically developing children (low-risk). The K99 study aims to identify early shared and distinct predictors of the development of dimensionally-measured ASD versus ADHD symptoms at 24 months of age across key cognitive, language, social, and behavioral domains at 12 and 18 months of age. The R00 study will build upon the K99 study, following an independent sample of infants through 36 months and incorporating additional measurement strategies and categorical diagnostic outcomes, allowing for the examination of shared and distinct early developmental trajectories of children with ASD versus ADHD diagnostic outcomes. Within each study, multi-method, multi-informant, multidimensional evaluations will include direct behavioral assessments, eye tracking, parent-completed rating scales, and examiner- completed ratings. These studies will be critical for (a) elucidating shared versus distinct developmental pathways; (b) accurate early screening, assessment, and differential diagnosis; and (c) determining key domains and time points for the development of targeted, process-focused intervention and prevention programs that can be applied early in life across many groups of individuals with, or at risk for, various diagnoses, consistent with the NIH Research Domain Criteria (RDoC) goals.

PROJECT SUMMARY/ABSTRACT By the time they are typically detected, attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are already challenging to treat. ADHD is characterized, in part, by deficits in self-regulation, while social communication deficits are a hallmark of ASD. Although traditional diagnostic definitions imply distinct phenotypes, co-occurrence is common with evidence of shared heritability, but little is known about overlapping versus unique markers and mechanisms early in development. Putative shared processes include dysregulation of attention and affect. Based on links with these processes, respiratory sinus arrhythmia (RSA), an index of parasympathetic nervous system (PNS) functioning reflecting effort allocation and emotion regulation, has been suggested as a potential transdiagnostic biomarker. No prior studies have examined shared versus distinct contributions of atypical infant PNS functioning, attention regulation, and affect regulation to later self-regulation and social communication deficits in infants at genetic risk for such challenges. Moreover, few studies have characterized continuity of symptoms across early childhood in high-risk samples, nor have infant predictors of symptom continuity been examined. Addressing these points is imperative to enhancing early detection efforts, delineating mechanisms underlying symptom development, identifying targets and time points for prevention and intervention, and determining novel markers of treatment efficacy. This proposal seeks to better understand developmental pathways to the Research Domain Criteria (RDoC) domains of cognitive systems (cognitive control/self-regulation) and social processes (social communication) across early development in a sample enriched for such challenges: infants at familial risk for ASD (n = 60), familial risk for ADHD (n = 60), and low risk for both (n = 40). We aim to: (1) identify shared and distinct early behavioral and physiological markers of, and mechanisms underlying, self-regulation and social communication problems among infants at risk, and (2) evaluate continuity of self-regulation and social communication problems across early childhood, including delineation of infant predictors of such continuity. Leveraging previous NIH support (K99/R00 MH106642) and employing a multi-method, multi-informant, multi-dimensional design, infants will be evaluated at 6 or 9, 12, 18, 24, and 36 months of age with a focus on trajectories and mediational mechanisms. This R01 proposal responds to the NIMH Strategic Plan to ?Define the Mechanisms of Complex Behaviors? and ?Chart Mental Illness Trajectories to Determine When, Where, and How to Intervene.? Exploring shared versus distinct mechanisms underlying the development of self-regulation and social communication symptoms will improve early identification of disorders like ADHD and ASD and encourage the development of transdiagnostic, process-focused early interventions, consistent with RDoC goals.