Determining Crustal Attenuation With Seismic <i>T</i> Waves in Southern Africa

Yong, Zhou; Chen, Xiaofei; Ni, Sidao; Qian, Yunyi; Yayun, Zhang; Yu, Changqing; Zhong, Qiu; Zheng, Tingting; Xu, Min

doi:10.1029/2021gl094410

Cited by 3 publications

(2 citation statements)

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“…T ‐waves exhibit spindle‐shaped, high‐frequency (>1 Hz) waveforms on hydrophones (Fox et al., 1995), ocean bottom seismometers (OBS; Hamada, 1985), autonomous MERMAID floats (Simon et al., 2021), and even land stations (e.g., Buehler & Shearer, 2015). Since their early documentations in the 1930s (Collins, 1936; Jaggar, 1930), T ‐waves have been widely used to monitor oceanic seismicity (Dziak et al., 2004; Fox et al., 2001; Hanson & Bowman, 2006; Parnell‐Turner et al., 2022; Smith et al., 2002) and volcanism (Tepp & Dziak, 2021; Wech et al., 2018), promote tsunami warning (Matsumoto et al., 2016; Okal & Talandier, 1986), determine earthquake properties (de Groot‐Hedlin, 2005; Walker et al., 1992), discriminate explosive and seismic sources (Talandier & Okal, 2001, 2016), infer detached slabs (Okal, 2001), and constrain crustal attenuation (Koyanagi et al., 1995; Zhou et al., 2021), significantly broadening our understanding of tectonic process in the remote ocean (Dziak et al., 2012) and seismo‐acoustic wave genesis and propagation (Okal, 2008).…”

Section: Introductionmentioning

confidence: 99%

Ocean Bottom Distributed Acoustic Sensing for Oceanic Seismicity Detection and Seismic Ocean Thermometry

Shen,

2024

JGR Solid Earth

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A T‐wave is a seismo‐acoustic wave that can travel a long distance in the ocean with little attenuation, making it valuable for monitoring remote tectonic activity and changes in ocean temperature using seismic ocean thermometry (SOT). However, current high‐quality T‐wave stations are sparsely distributed, limiting the detectability of oceanic seismicity and the spatial resolution of global SOT. The use of ocean bottom distributed acoustic sensing (OBDAS), through the conversion of telecommunication cables into dense seismic arrays, is a cost‐effective and scalable means to complement existing seismic stations. Here, we systematically investigate the performance of OBDAS for oceanic seismicity detection and SOT using a 4‐day Ocean Observatories Initiative community experiment offshore Oregon. We first present T‐wave observations from distant and regional earthquakes and develop a curvelet denoising scheme to enhance T‐wave signals on OBDAS. After denoising, we show that OBDAS can detect and locate more and smaller T‐wave events than regional OBS network. During the 4‐day experiment, we detect 92 oceanic earthquakes, most of which are missing from existing catalogs. Leveraging the sensor density and cable directionality, we demonstrate the feasibility of source azimuth estimation for regional Blanco earthquakes. We also evaluate the SOT performance of OBDAS using pseudo‐repeating earthquake T‐waves. Our results show that OBDAS can utilize repeating earthquakes as small as M3.5 for SOT, outperforming ocean bottom seismometers. However, ocean ambient natural and instrumental noise strongly affects the performance of OBDAS for oceanic seismicity detection and SOT, requiring further investigation.

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Section: Introductionmentioning

confidence: 99%

Ocean Bottom Distributed Acoustic Sensing for Oceanic Seismicity Detection and Seismic Ocean Thermometry

Shen,

2024

JGR Solid Earth

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“…"The mechanism of coupling from acoustic waves to seismic waves is not clear but has been proposed to be related to the slope of the seafloor near the shore, and the contrast." "The T phase does not depend only on the earthquakes' magnitude, but also on the depth where earthquakes occur, the continental slope, the conversion location, and the conversion efficiency" [28] • Do T waves themselves constitute a disaster hazard?…”

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confidence: 99%

Citizen Science and The University of Queensland Seismograph Stations (UQSS)—A Study of Seismic T Waves in S-W Pacific Ocean

Lynam¹,

Karunaratne²

2023

Sustainability

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Seismologists listen to Earth’s noise as it rips apart (faulting), exudes (volcanoes) and swallows (subducts) large volumes of rock. Your mobile phone is most likely detecting such noise, right now! This paper is about one such specific noise, the T wave. It summarises an early and successful piece of citizen science, performed within The University of Queensland Seismograph Stations (UQSS) observatory, in cooperation with colleagues at CSIRO. It was designed to encourage young STEM students from Brisbane high schools to engage in “real” research, back in 1995. Bear in mind, this is a time period when science is changing considerably from analog to digital media and operational recording methods. The citizen science students used a pre-prepared decadal collection (1980–1990) of T waves, derived from the Brisbane seismograph (BRS) observatory data catalogue. BRS has been operating since 1937 and is part of the global World-Wide Seismograph Station Network (WWSSN). Fortunately, seismology is a very collaborative field. There is a lot of data analysis involved in the science of recording earthquake signals, with auxiliary definitive catalogues, observers logbooks, housing of the recordings themselves (analog and digital) and the software mediums that change over time. It equally tests housekeeping proficiency, where a maze of record-keeping problems can be encountered in a longitudinal data collection study such as this. Having completed the project report, Earthquake generated T phases on BRS Seismograph (Brisbane, Q’ld) a predictor for Tasman Sea Tsunamis? their (analog) results sat in a cupboard until recently. The project was re-analysed in 2022 for a higher-degree student, discovering a timely climate change implication for the study. The original research question has now been amplified with a brief literature review. We observe that currently in Australia, university and government earth science observatories have diminished, and in their place, public seismic networks (PSN) have evolved, either in backyard sheds or school science labs. We now additionally propose here that the level of expertise required ideally fits the role of advancing citizen science, for a real science advantage. This is already a topical citizen disaster preparedness action area, and we propose that it has applications as a possible educational strategy for citizen engagement in today’s climate emergency. In addition, we are hopeful that other researchers in oceanography will read this paper and decide to explore the ocean’s temperature rise phenomenon through the eyes of seismological observers.

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Seismic T Phases in the Western-Central Mediterranean: Source of Seismic Hazard?

De Caro,

Montuori,

Frugoni

et al. 2023

Seismological Research Letters

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The Algerian offshore earthquake of 18 March 2021, Mw 6.0, was felt by people in various Italian regions, also at large epicentral distance. This unusual human perception far from the source prompted us to analyze the waveforms recorded by land seismic stations installed along the Iberian, French, and Italian coasts. On some seismograms of the selected network, prominent T phases are detected. T waves can travel in the SOund Fixing And Ranging (SOFAR) channel over great distances (thousands of kilometers) with little loss in signal strength and be recorded by near-coastal seismometers after the P (primary) and S (secondary) phases (hence T or tertiary phases). To explain the subjective perception of ground shaking with quantities that are measured on the seismogram, we estimated the empirical macroseismic intensities for both body and T phases and we calculated the body-wave seismic attenuation. The P-wave anelastic attenuation analysis shows two main wave propagation patterns that reflect lithosphere heterogeneity of the Algerian, Liguro-Provençal, and Tyrrhenian basins. We find that in some cases, in particular along the Italian and French coasts, the largest ground shaking is caused by the T phase. Our observations confirm that the central-western Mediterranean Sea is a favorable site for T-wave propagation and suggest that the T phases should be taken into account in ground-shaking hazard assessment for the central-western Mediterranean.

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Determining Crustal Attenuation With Seismic T Waves in Southern Africa

Abstract: Although intraplate seismicity is lower than interplate seismicity, seismic hazards in stable continents are not negligible (

Cited by 3 publications

References 70 publications

Ocean Bottom Distributed Acoustic Sensing for Oceanic Seismicity Detection and Seismic Ocean Thermometry

Ocean Bottom Distributed Acoustic Sensing for Oceanic Seismicity Detection and Seismic Ocean Thermometry

Citizen Science and The University of Queensland Seismograph Stations (UQSS)—A Study of Seismic T Waves in S-W Pacific Ocean

Seismic T Phases in the Western-Central Mediterranean: Source of Seismic Hazard?

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