A real-time early warning seismic event detection algorithm using smart geo-spatial bi-axial inclinometer nodes for Industry 4.0 applications

Earthquakes are one of the major natural calamities as well as a prime subject of interest for seismologists, state agencies, and ground motion instrumentation scientists. The real-time data analysis of multi-sensor instrumentation is a valuable knowledge repository for real-time early warning and trustworthy seismic events detection. In this work, an early warning in the first 1 micro-second and seismic wave detection in the first 1.7 milliseconds after event initialization is proposed using a seismic wave event detection algorithm (SWEDA). The SWEDA with nine low-computation-cost operations is being proposed for smart geospatial bi-axial inclinometer nodes (SGBINs) also utilized in structural health monitoring systems. SWEDA detects four types of seismic waves, i.e., primary (P) or compression, secondary (S) or shear, Love (L), and Rayleigh (R) waves using time and frequency domain parameters mapped on a 2D mapping interpretation scheme. The SWEDA proved automated heterogeneous surface adaptability, multi-clustered sensing, ubiquitous monitoring with dynamic Savitzky-Golay filtering and detection using nine optimized sequential and structured event characterization techniques. Furthermore, situation-conscious (context-aware) and automated computation of short-time average over long-time average (STA/LTA) triggering parameters by peak-detection and run-time scaling arrays with manual computation support were achieved. - 2019 by the authors.Funding: This publication was made possible by the NPRP grant # 8-1781-2-725 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

Characterization of harmonic tremor at Santiaguito volcano and its implications for eruption mechanisms

We observed Santiaguito volcano in southwestern Guatemala from March 2008 - March 2010. Seismic and infrasound data collected between January and March of 2009 contain records of many diverse processes occurring at the dacitic dome complex, including the recurrence of short lived (30-200 seconds in duration) harmonic tremor concurrent with ash poor gas emissions from the volcano. We employ several different analytical techniques to examine different portions of the tremor and source mechanisms. We use the parameters derived by this analysis to compare the feasibility of several suggested models of eruption mechanisms, and determine that this type of harmonic tremor is most justifiably generated by the flow of gas through crack networks generated by shear fracture along the magma conduit margin

Teleseismic earthquake wavefields observed on the ross ice shelf

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Baker, M. G., Aster, R. C., Wiens, D. A., Nyblade, A., Bromirski, P. D., Gerstoft, P., & Stephen, R. A. Teleseismic earthquake wavefields observed on the Ross Ice Shelf. Journal of Glaciology, 67(261), (2021): 58-74, https://doi.org/10.1017/jog.2020.83.Observations of teleseismic earthquakes using broadband seismometers on the Ross Ice Shelf (RIS) must contend with environmental and structural processes that do not exist for land-sited seismometers. Important considerations are: (1) a broadband, multi-mode ambient wavefield excited by ocean gravity wave interactions with the ice shelf; (2) body wave reverberations produced by seismic impedance contrasts at the ice/water and water/seafloor interfaces and (3) decoupling of the solid Earth horizontal wavefield by the sub-shelf water column. We analyze seasonal and geographic variations in signal-to-noise ratios for teleseismic P-wave (0.5–2.0 s), S-wave (10–15 s) and surface wave (13–25 s) arrivals relative to the RIS noise field. We use ice and water layer reverberations generated by teleseismic P-waves to accurately estimate the sub-station thicknesses of these layers. We present observations consistent with the theoretically predicted transition of the water column from compressible to incompressible mechanics, relevant for vertically incident solid Earth waves with periods longer than 3 s. Finally, we observe symmetric-mode Lamb waves generated by teleseismic S-waves incident on the grounding zones. Despite their complexity, we conclude that teleseismic coda can be utilized for passive imaging of sub-shelf Earth structure, although longer deployments relative to conventional land-sited seismometers will be necessary to acquire adequate data.This research was supported by NSF grants PLR-1142518, 1141916, 1142126, 1246151, 1246416 and OPP-1744852 and 1744856

Damage detection in reinforced concrete and self-healing concrete structures using non-destructive testing techniques

This thesis mainly contains the investigation of the role of Acoustic Emission (AE) and Acousto-Ultrasonics (AU) as the Non-Destructive Testing (NDT) techniques for concrete structure. Further the techniques applied in this work explored the application and feasibility of AE to monitor and characterise the behaviour of the recently developed self-healing concrete structure. Experimental studies were conducted on a range of specimen in different scale, focusing on the development and application of experimental techniques and data analysis methods for source characterisation, damage detection, location and assessment of AE. The four main topics and findings are as follows: 1. Characterisation of basic failure mode on concrete member Considering the complexity of AE signals of concrete structure, a fundamental study on the source characterisation of two basic failure mode of concrete is conducted using a combined method of parametric analysis and waveform analysis. The maximum amplitude and corresponding characteristic instantaneous frequency are extracted as two indicators of basic failure mode to characterise the complex damage source in concrete. 2. Characterisation of AE source using Moment Tensor Analysis (MTA) A detailed experimental investigation of Moment Tensor Analysis (MTA) is conducted on a concrete cube to elucidate the SiGMA procedure performed by the H-N source. Then the MTA results obtained from a bending testing on a RC beam shows a promising agreement with results obtained via the conventional parameter-based method. Comparison between different methods is discussed and concluded. 3. Laboratory investigations on AE monitoring of self-healing behaviours The applicability of AE techniques to monitor the whole damage and healing process of the vascular-network based self-healing system is evaluated and was found that the Kaiser effect and Felicity ratio could be applied as an indicator to assess the healing efficiency. Principal Component Analysis and unsupervised pattern recognition techniques are adopted to differentiate between concrete fracture signals and other sources. 4. Crack size monitoring and measurement using ultrasonic testing method Experimental studies are conducted using Acousto-Ultrasonics on a range of different size specimen to monitor and measure the crack development. The prospect and potential application of the AU technique investigating impact of healing agent of vascular network-based system were explored