Search Results (3)

The importance of monitoring earthquakes for disaster management, public safety, and scientific research can hardly be overstated. The emergence of low-cost seismic sensors offers potential for widespread deployment due to their affordability. Nevertheless, vehicular noise in low-cost seismic sensors presents as a significant challenge in urban environments where such sensors are often deployed. In order to address these challenges, this work proposes the use of an amalgamated deep neural network constituent of a DNN trained on earthquake signals from professional sensory equipment as well as a DNN trained on vehicular signals from low-cost sensors for the purpose of earthquake identification in signals from low-cost sensors contaminated with vehicular noise. To this end, we present low-cost seismic sensory equipment and three discrete datasets that—when the proposed methodology is applied—are shown to significantly outperform a generic stochastic differential model in terms of effectiveness and efficiency. Full article

Noting the importance of evaluating near-surface geology in earthquake risk assessment, we explored the application to the Jakarta Basin of a relatively new and simple technique to map shallow seismic structure using body-wave polarization. The polarization directions of P-waves are sensitive to shear-wave velocities (V_s), while those of S-waves are sensitive to both body-wave velocities. Two dense, temporary broadband seismic networks covering Jakarta city and its vicinity were operated for several months, firstly, from October 2013 to February 2014 consisting of 96 stations, and secondly, between April and October 2018 consisting of 143 stations. By applying the polarization technique to earthquake signals recorded during these deployments, the apparent half-space shear-wave velocity (V_s^ahs) beneath each station is obtained, providing spatially dense coverage of the sedimentary deposits and the edge of the basin. The results showed that spatial variations in V_s^ahs obtained from polarization analysis are compatible with previous studies, and appear to reflect the average V_s of the top 150 m. The low V_s that characterizes sedimentary deposits dominates most of the area of Jakarta, and mainly reaches the outer part of its administrative margin to the southwest, more than 10 km away. Further study is required to obtain a complete geometry of the Jakarta Basin. In agreement with previous studies, we found that the polarization technique was indeed a simple and effective method for estimating near-surface V_s that can be implemented at very low-cost wherever three-component seismometers are operated, and it provides an alternative to the use of borehole and active source surveys for such measurements. However, we also found that for deep basins such as Jakarta, care must be taken in choosing window lengths to avoid contamination of basement converted phases. Full article

The Nyingchi Mw 6.4 earthquake on 17 November 2017 is the first large event since 1950 at the southeast end of the Jiali fault. This event was captured by interferometric synthetic aperture radar (InSAR) measurements from the European Space Agency (ESA) Sentinel-1A radar satellite, which provide the potential to determine the fault plane, as well as the co-seismic slip distribution, and understand future seismic hazards. However, due to the limited magnitude of surface displacements and the strong topography variations, InSAR-derived co-seismic signals are contaminated by strong tropospheric effects which makes it difficult (if not impossible) to determine the source parameters and co-seismic slip distribution. In this paper, we employ the Generic Atmospheric Correction Online Service for InSAR (GACOS) to generate correction maps for the co-seismic interferograms, and successfully extract co-seismic surface displacements for this large event. The phase standard deviation after correction for a seriously-contaminated interferogram reaches 0.8 cm, significantly improved from the traditional phase correlation analysis (1.13 cm) or bilinear interpolation (1.28 cm) methods. Our best model suggests that the seismogenic fault is a NW–SE striking back-thrust fault with a right-lateral strike slip component. This reflects the strain partitioning of NE shortening and eastward movement of the Eastern Tibetan plateau due to the oblique convergence between the Indian and Eurasian plates. Full article