Seismic Monitoring System Calibration Using Ground Truth Database

Calibration of a seismic monitoring system remains a major issue due to the lack of ground truth information and uncertainties in the regional geological parameters. Rapid and accurate identification of seismic events is currently not feasible due to the absence of a fundamental framework allowing immediate access to ground truth information for many parts of the world. Precise location and high-confidence identification of regional seismic events are the primary objectives of monitoring research in seismology. In the Department of Energy Knowledge Base (KB), ground truth information addresses these objectives and will play a critical role for event relocation and identification using advanced seismic analysis tools. Maintaining the KB with systematic compilation and analysis of comprehensive sets of geophysical data from various parts of the world is vital. The goal of this project is to identify a comprehensive database for China using digital seismic waveform data that are currently unavailable. These data may be analyzed along with ground truth information that becomes available. To date, arrival times for all regional phases are determined on all events above Mb 4.5 that occurred in China in 2000 and 2001. Travel-time models are constructed to compare with existing models. Seismic attenuation models may be constructed to provide better understanding of regional wave propagation in China with spatial resolution that has not previously been obtained

Grant No DE-FG02-03ER83720 Report for US Department of Engery

Effective and reliable nuclear monitoring requires discrimination between small magnitude explosions and earthquakes based on the use of limited regional data. Lg is generally the largest seismic phase from both explosion and earthquake sources recorded at regional distances. For small events, Lg may sometimes be the only well-recorded seismic phase so that discriminants based only on the use of Lg are especially desirable. Recent research has provided significantly better understanding of Lg by demonstrating that the explosion-generated Rg makes significant contribution to the low-frequency S or Lg from explosions. Near-source scattering of explosion-generated Rg appears to be a viable mechanism for generating low-frequency(< 2 Hz) Lg waves from explosions. Detailed knowledge of the complex scattering process is, however, still incomplete and is in fact the subject of several ongoing studies. Our analysis of regional data from nuclear explosions from both Nevada Test Site (NTS) and Kazakh Test Site (KTS) and nearby earthquakes in Phase I has suggested that there are several reliable source discrimination methods only based on the use of Lg at regional distances. These discriminants should be. especially useful for small magnitude seismic events for which Lg may be the only well-recorded seismic phase. Our results suggest four possible regional discriminants: (a) frequency-amplitude-time analysis of spectrograms, (b) Lg(low frequency)/Lg(high frequency), (c) Lg spectral slopes, and (d) skewness of Lg spectra. Remarkable similarity of discrimination results from both NTS and KTS nuclear explosions and nearby earthquakes, with entirely different geological settings, indicates that our results should be applicable to other regions of the world

Forced Rayleigh Scattering from Lipid-Water Smectic Phases

The hydrodynamic relaxation rate for water inhomogeneities in aligned lipid-water smectics is measured for the first time using an improved version of the "forced Rayleigh" technique. Variation of the relaxation rate with water concentration yields a distinction between "bound" and "free" water.Engineering and Applied Science

Multistep modelling of teleseismic receiver functions combined with constraints from seismic tomography: Crustal structure beneath southeast China

With a growing number of modern broad-band seismographic stations in Asia, the conditions have improved to allow higher resolution structural studies on regional scales. Here, we perform a receiver-based study of the lithosphere of southeast China using waveform records of excellent quality from 14 Chinese National Digital Seismic Network and four Global Seismic Network stations. Calculating the theoretical receiver functions (RFs) that match the observed RFs from teleseismic waveforms is an established technique for retrieving information about crustal and upper mantle structure beneath a seismic receiver. RFs, however, are predominantly sensitive to the gradients in the lithospheric elastic parameters, and it is impossible to determine a non-unique distribution of seismic parameters such as absolute shear wave speeds as a function of depth unless other geophysical data are combined with RFs. Thus, we combine RFs with independent information from shear and compressional wave speeds above and below the Mohorovičić discontinuity, available from the existing tomographic studies. We introduce a statistical approach for automatically selecting only mutually coherent RFs from a large set of observed waveforms. Furthermore, an interactive forward modelling software is introduced and applied to observed RFs to define a prior, physically acceptable range of elastic parameters in the lithosphere. This is followed by a grid-search for a simple crustal structure. An initial model for a linearized, iterative inversion is constructed from multiple constraints, including results from the grid-search for shear wave speed, the Moho depth versus vp/vs ratio domain search and tomography. The thickness of the crust constrained by our multistep approach appears to be more variable in comparison with tomographic studies, with the crust thinning significantly towards the east. We observe low values of vp/vs ratios across the entire region, which indicates the presence of a very silicic crust. We do not observe any correlation between the crustal thickness or age of the crust with vp/vs ratios, which argues against a notion that there is a simple relationship between mineralogical composition and crustal thickness and age on a global scale

A narrative synthesis of the impact of primary health care delivery models for refugees in resettlement countries on access, quality and coordination

Introduction. Refugees have many complex health care needs which should be addressed by the primary health care services, both on their arrival in resettlement countries and in their transition to long-term care. The aim of this narrative synthesis is to identify the components of primary health care service delivery models for such populations which have been effective in improving access, quality and coordination of care. Methods. A systematic review of the literature, including published systematic reviews, was undertaken. Studies between 1990 and 2011 were identified by searching Medline, CINAHL, EMBASE, Cochrane Library, Scopus, Australian Public Affairs Information Service-Health, Health and Society Database, Multicultural Australian and Immigration Studies and Google Scholar. A limited snowballing search of the reference lists of all included studies was also undertaken. A stakeholder advisory committee and international advisers provided papers from grey literature. Only English language studies of evaluated primary health care models of care for refugees in developed countries of resettlement were included. Results: Twenty-five studies met the inclusion criteria for this review of which 15 were Australian and 10 overseas models. These could be categorised into six themes: service context, clinical model, workforce capacity, cost to clients, health and non-health services. Access was improved by multidisciplinary staff, use of interpreters and bilingual staff, no-cost or low-cost services, outreach services, free transport to and from appointments, longer clinic opening hours, patient advocacy, and use of gender-concordant providers. These services were affordable, appropriate and acceptable to the target groups. Coordination between the different health care services and services responding to the social needs of clients was improved through case management by specialist workers. Quality of care was improved by training in cultural sensitivity and appropriate use of interpreters. Conclusion: The elements of models most frequently associated with improved access, coordination and quality of care were case management, use of specialist refugee health workers, interpreters and bilingual staff. These findings have implications for workforce planning and training