Search

Can a P-wave detection algorithm enhance the performance of an Earthquake Early Warning System (EEWS), particularly in community-engaged networks of low-cost ground motion sensors susceptible to noise? If so, what P-wave detection algorithm would perform the best? This study analyses the performance of four different P-wave detection algorithms using a community-engaged Earthquake Early Warning (EEW) network. The ground motion data from a 48-hour time window around a M5.8 earthquake on 22 September 2022 were used as the basis for this case study, where false and missed detections were analysed for each P-wave detection algorithm. The results indicate that a wavelet transformation-based P-wave picker is the most suitable algorithm for detecting an earthquake with minimal missed and false detections for a community-engaged EEWS. Our results show that a citizen seismology-based EEWS is capable of detecting events of interest to EEW when selecting an appropriate earthquake detection algorithm. The study also suggests future research areas for community-engaged EEWSs, including dynamically changing P-wave detection thresholds and improving citizen seismologists’ user experience and involvement. [ABSTRACT FROM AUTHOR]

Gunung Merapi (Mountain of Fire) is the guardian of a cosmogonic-sacred landscape, and one of the most dangerous volcanoes in the world. Its eruptions are well studied, however, the relationships among ritual, science, protection and grassroots disaster management arising after the 2006 and 2010 eruptions are mostly overlooked. This paper fills this gap in the literature, through qualitative research that explores local perceptions and places respiratory protection in a larger ecology of protective practices during, and after, volcanic crises. In a previous study, 99% of respondents in Yogyakarta used masks to protect from inhaling volcanic ash. In order to understand the respiratory protective practices developed, in the last decade, to cope with Merapi's eruptions, we need to engage with the emergence of the local volunteer-led grassroots monitoring systems. Although these networks were formalised by agencies, they were originally set-up in a bottom-up fashion to respond to pyroclastic flows and other life-threatening volcanic hazards. Our research found that they play a key role in the distribution of masks and respiratory health narratives, thus influencing the wide adoption of certain types of respiratory protection. Disaster management agencies, village heads, ritual experts and volunteers participating in these monitoring networks share spiritual signals (dreams) and scientific ones (seismic data, health narratives) and masks as part of their response to volcanic crises. Our findings about these Merapi networks challenge dominant assumptions in the Disaster Risk Reduction literature that tend to equate building resilience with the substitution of problematic 'cultural beliefs' for 'scientific facts'. [ABSTRACT FROM AUTHOR]

The ground vibrations observed in Taiwan during three teleseismic earthquakes in 2011 by broadband seismometers near major science parks were investigated. Their frequency content was exhibited via spectral analysis, and their effect on structures was examined by response spectra. To assess their possible impact on vibration-sensitive facilities, three vibration criteria in terms of velocity or displacement were utilized. Their predominant frequencies were between 0.04– and 0.16 Hz and somewhat dependent on focal depth and site geology, and they were therefore only influential to very long-period structures. However, the vibration levels exceeded the adopted criteria to some extent, especially at the softer site. [ABSTRACT FROM AUTHOR]

Due to the limited number of seismic records in the soil and inefficient use of one-dimensional wave theory in the estimation of vertical components for seismic waves, this paper studies depth coherency (coherency between the surface seismic waves and that at depth) in order to describe seismic acceleration at different depths based on surface seismic acceleration signals. In this study, the authors utilized data from the KiK network to investigate the variability of seismic ground motions with depth and obtain a model to simulate coherency of depth-dependent ground motions. Furthermore, by using the methodology described in the Chinese Code for the Seismic Design of Buildings, the authors categorized a number of test locations based on the depth and shear velocity of the soil cover. Four different types of sites were defined and both the horizontal and vertical components of ground motion from strong motion seismometers were analyzed. The results show that there is no significant dependence between the estimated coherencies from different earthquake magnitudes or epicentral distance (less than 200 km). Moreover, the behavior of depth coherency is site-dependent and there are notable differences between horizontal and vertical depth coherency. In addition, existing spatial coherency models may not provide a satisfactory estimate of the variation of depth coherency. [ABSTRACT FROM AUTHOR]