An earthquake early warning (EEW) system is a real‐time seismic monitoring infrastructure that has the capability to provide warnings to target cities before the arrival of the strongest shaking waves. In order to provide a rapid alert when targets are very close to the epicenter of the events, we developed an on‐site EEW approach and evaluated its performance at the Italian national scale. The system is a P wave‐based method that measures in real time two parameters: the initial peak displacement (Pd) and the average period (τc). As output, the system provides the predicted ground‐shaking intensity at the monitored site, the alert level, and a qualitative classification of both earthquake magnitude and source‐to‐receiver distance. We applied the on‐site EEW methodology to a data set of Italian earthquakes, with magnitude ranging from 3.8 to 6, and evaluated the performance of the system in terms of correct warning and lead times (i.e., time available for security actions at the target). The results of this retrospective analysis show that for the large majority of the analyzed cases, the method is able to deliver a correct warning shortly after the P wave detection, with more than 80% of successful intensity predictions at the target site. The lead times increase with distance, with a value of 8–10 s at 50 km and 15–18 s at 100 km.
A new strategy for a P wave-based, on-site earthquake early warning system has been developed and tested on Japanese strong motion data. The key elements are the real-time, continuous measurement of three peak amplitude parameters and their empirical combination to predict the ensuing peak ground velocity. The observed parameters are compared to threshold values and converted into a single, dimensionless variable. A local alert level is issued as soon as the empirical combination exceeds a given threshold. The performance of the method has been evaluated by applying the approach to the catalog of Japanese earthquake records and counting the relative percentage of successful, missed, and false alarms. We show that the joint use of three peak amplitude parameters improves the performance of the system as compared to the use of a single parameter, with a relative increase of successful alarms of about 35%. The proposed methodology provides a more reliable prediction of the expected ground shaking and improves the robustness of a single-station, threshold-based earthquake early warning system.
Background This study was conducted to determine the seroprevalence of HIV among pregnant women in Brazil and to describe HIV testing coverage and the uptake of antenatal care (ANC). Methods Between October 2010 and January 2012, a probability sample survey of parturient women aged 15-49 years who visited public hospital delivery services in Brazil was conducted. Data were collected from prenatal reports and hospital records. Dried blood spot (DNS) samples were collected and tested for HIV. We describe the agespecific prevalence of HIV infection and ANC uptake with respect to sociodemographic factors. . 94% [0.28-3.10]). The HIV testing coverage during prenatal care was of 86.6% for one test and of 38.2% for two tests. Overall, 98.5% of women attended at least 1 ANC visit, 90.4% attended at least 4 visits, 71% attended at least 6 visits, and 51.7% received ANC during the 1st trimester. HIV testing coverage and ANC uptake indicators increased with increasing age and education level of education, and were highest in the Southern region. Conclusions Brazil presents an HIV prevalence of less than 1% and almost universal coverage of ANC. However, gaps in HIV testing and ANC during the first trimester challenge the prevention of the vertical transmission of HIV. More efforts are needed to address regional and social disparities.
Pereira GFM conceived, wrote and validated the article. Pimenta MC and Guimarães MDC contributed to the conception, analysis, writing and critical review of the intellectual content. Giozza SP acquired the data and wrote the article. Caruso AR reviewed and validated the data. Bastos FI contributed to the critical review of the content.
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