Geometric and Level Set Tomography using Ensemble Kalman Inversion

Tomography is one of the cornerstones of geophysics, enabling detailed spatial descriptions of otherwise invisible processes. However, due to the fundamental ill-posedness of tomography problems, the choice of parametrizations and regularizations for inversion significantly affect the result. Parametrizations for geophysical tomography typically reflect the mathematical structure of the inverse problem. We propose, instead, to parametrize the tomographic inverse problem using a geologically motivated approach. We build a model from explicit geological units that reflect the a priori knowledge of the problem. To solve the resulting large-scale nonlinear inverse problem, we employ the efficient Ensemble Kalman Inversion scheme, a highly parallelizable, iteratively regularizing optimizer that uses the ensemble Kalman filter to perform a derivative-free approximation of the general iteratively regularized Levenberg–Marquardt method. The combination of a model specification framework that explicitly encodes geological structure and a robust, derivative-free optimizer enables the solution of complex inverse problems involving non-differentiable forward solvers and significant a priori knowledge. We illustrate the model specification framework using synthetic and real data examples of near-surface seismic tomography using the factored eikonal fast marching method as a forward solver for first arrival traveltimes. The geometrical and level set framework allows us to describe geophysical hypotheses in concrete terms, and then optimize and test these hypotheses, helping us to answer targeted geophysical questions

Rayleigh-Wave H/V via Noise Cross Correlation in Southern California

We study the crustal structure of southern California by inverting horizontal‐to‐vertical (H/V) amplitudes of Rayleigh waves observed in noise cross‐correlation signals. This study constitutes a useful addition to traditional phase‐velocity‐based tomographic inversions due to the localized sensitivity of H/V measurements to the near surface of the measurement station site. The continuous data of 222 permanent broadband stations of the Southern California Seismic Network (SCSN) were used in production of noise cross‐correlation waveforms, resulting in a spatially dense set of measurements for the southern California region in the 1–15 s period band. The fine interstation spacing of the SCSN allows retrieval of high signal‐to‐noise ratio Rayleigh waves at periods as low as 1 s, significantly improving the vertical resolution of the resulting tomographic image, compared to previous studies with minimum periods of 5–10 s. In addition, horizontal resolution is naturally improved by increased station density. Tectonic subregions including the Los Angeles basin and Salton trough are clearly visible due to their high short‐period H/V ratios, whereas the Transverse and Peninsular Ranges exhibit low H/V at all periods

Did Oldham Discover the Core After All? Handling Imprecise Historical Data with Hierarchical Bayesian Model Selection Methods

Historical seismic data are essential to fill in the gaps in geophysical knowledge caused by the low rate of significant seismic events. Handling historical data in the context of geophysical inverse problems requires special care, due to the large errors in the data collection process. Using Oldham’s data for the discovery of Earth’s core as a case study, we illustrate how a hierarchical Bayesian model selection methodology using leave‐one‐out cross validation can robustly and efficiently answer quantitative questions using even poor‐quality geophysical data. We find that there is statistically significant evidence for the existence of the core using only the P‐wave data that Oldham effectively discarded in his discussion

Recovery-Oriented Training and Staff Attitudes Over Time in Two State Hospitals

Recovery attitudes and concepts are often promoted to community mental health staff through educational and in-service trainings, but no study found has examined this in state hospitals. The current observational study aimed to examine the types of recovery-oriented trainings that occurred at two state hospitals over 1 year and subsequent changes in staff recovery attitudes. A total of 184 state hospital staff completed questionnaires assessing their personal optimism, consumer optimism, and agency recovery orientation at baseline and 1 year later. The types of recovery-oriented trainings staff received were categorized as general/inspirational or specific/practical training. Results found that the majority of staff at the two state hospitals received some recovery-oriented training, mostly general/inspirational training. Staff who received specific/practical training had a greater increase in agency recovery attitudes than staff who received only general/inspirational training or no training. However, the more trainings staff had, the higher their consumer optimism. These results suggest state hospitals are incorporating recovery-oriented staff trainings, but more specific trainings may be needed and all staff involved in different levels of care need to be included

Staff Turnover in Statewide Implementation of ACT: Relationship with ACT Fidelity and Other Team Characteristics

Staff turnover on assertive community treatment (ACT) teams is a poorly understood phenomenon. This study examined annual turnover and fidelity data collected in a statewide implementation of ACT over a 5-year period. Mean annual staff turnover across all observations was 30.0%. Turnover was negatively correlated with overall fidelity at Year 1 and 3. The team approach fidelity item was negatively correlated with staff turnover at Year 3. For 13 teams with 3 years of follow-up data, turnover rates did not change over time. Most ACT staff turnover rates were comparable or better than other turnover rates reported in the mental health and substance abuse literature

Utilization profiles of VA homeless programs

The Department of Veterans Affairs (VA) has invested in developing and operating a continuum of various specialized homeless assistance programs, including domiciliary care, transitional housing, permanent supported housing, rapid rehousing, and others. Prior research has examined the characteristics, service use, and housing outcomes of Veterans participating in individual VA homeless programs (Tsai, Kasprow, & Rosenheck, 2013; Tsai, O'Toole, & Kearney, 2017). However, examining participation in these programs in isolation ignores the fact that Veterans are likely to be eligible for (and may access) multiple programs over time. Thus, it is important to analyze longitudinal data on use of all VA homeless programs together to understand how Veterans may use programs in combination, the sequence in which these programs are used, and for what periods of time. In this study, we profiled how Veterans use multiple VA homeless programs over time. Further, we examined how their profiles are related to sociodemographic characteristics and other VA health service use. The results may inform continued development and program planning of VA homeless programs. The specific aims of the project were: 1) to identify temporal typologies and pathways to Veterans’ use of various VA homeless programs; and 2) to examine Veteran characteristics associated with different patterns of VA homeless services utilization.https://content.govdelivery.com/attachments/USVHACENTER/2018/08/15/file_attachments/1055639/Utilization%2Bprofiles%2Bof%2BVA%2Bhomeless%2Bprograms_Tsai%2526Byrne_August%2B2018.pdfhttps://content.govdelivery.com/attachments/USVHACENTER/2018/08/15/file_attachments/1055639/Utilization%2Bprofiles%2Bof%2BVA%2Bhomeless%2Bprograms_Tsai%2526Byrne_August%2B2018.pdfPublished versio