Seismic ocean thermometry

Wu, Wenbo; Zhan, Zhongwen; Peng, Shirui; Ni, Sidao; Callies, Jörn

doi:10.1126/science.abb9519

Cited by 60 publications

(85 citation statements)

References 58 publications

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“…They can be excited by earthquakes through the conversion of elastic energy into acoustic waves at the solid-liquid interface (e.g., Talandier and Okal, 1998;Park et al, 2001). T waves recorded on seismograph and hydrophone networks have been used in a large number of studies including: small earthquake 11 detection and retrieval of seismic source properties in marine environments (Okal and Talandier, 1986), detection of volcanic activity (Talandier and Okal, 1987), underwater landslides (Fryer et al, 2004), or global climate change (Wu et al, 2020). T phases are useful to locate seismicity at mid-oceanic ridges because, due to the low attenuation at the SOFAR channel, they can transmit energy from relatively small sources over large epicentral distances.…”

Section: Hydroacoustic Phasesmentioning

confidence: 99%

Noise Levels and Signals Observed on Submarine Fibers in the Canary Islands Using DAS

Ugalde

Becerril

Villaseñor

et al. 2021

Seismological Research Letters

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In this study, we investigate 70 days of distributed acoustic sensing (DAS) recordings in the Canary Islands using an undersea fiber-optic telecommunication cable that links the islands of Tenerife and Gran Canaria. Two DAS interrogators connected to both ends of the cable turned the fiber into an array of 11,968 strain sensors covering a total length of ∼120 km. We present the details of the experiment, noise analysis, and examples of recorded signals. Seismic ambient noise levels assessment indicates poor local coupling of the cable due to the irregular bathymetry that results in high-amplitude acoustic oscillations in some channels. The DAS array recorded several types of nonseismic (vehicles, surface gravity waves, ships) and seismic signals. Local and regional earthquakes were detected with magnitudes mbLg≥2. Surface waves from teleseismic events at a distance of ∼3000 km were also identified in the strain recordings. Here, we report the first observations with DAS of hydroacoustic T waves generated by oceanic earthquakes located at the Central Mid-Atlantic Ridge and the Cape St. Vincent region. Events had magnitudes from Mw 4.2 to 6.9, and the hydroacoustic waves were recorded at epicentral distances from 780 to 3400 km. Our findings show that submarine fiber-optic cables can effectively be used to assess the seismic activity in remote oceanic areas.

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Section: Hydroacoustic Phasesmentioning

confidence: 99%

Noise Levels and Signals Observed on Submarine Fibers in the Canary Islands Using DAS

Ugalde

Becerril

Villaseñor

et al. 2021

Seismological Research Letters

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“…Studies based on observations have confirmed the warming of ocean waters since the last decades of the 20th century (Johnson & Lyman, 2020; Rhein et al., 2013; Strass et al., 2020; Wu et al., 2020). The rate of warming is mostly observed in the upper 2,000 m (Johnson & Lyman, 2020; Wu et al., 2020).…”

Section: Introductionmentioning

confidence: 95%

Warming Trend in Antarctic Bottom Water in the Vema Channel in the South Atlantic

Campos

Caspel

Zenk

et al. 2021

Geophysical Research Letters

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The excess heat absorbed from the atmosphere has increased the temperature in the upper layers of the ocean (<2,000 m). In the abyss, infrequently repeated ship sections, deep Argo float measurements, and sparse moored observations have found signs of warming in the Southwest Atlantic, possibly linked to changes in the Weddell Sea. We present a new moored temperature time series sampled near the bottom in the Vema Channel, from February 2019 to August 2020. Together with historical data, the combined record confirms the warming of the abyssal waters, with an increase of 0.059°C in potential temperature between January 1991 and August 2020, embedded within intense high‐frequency variability. Moreover, the data suggest the possibility of an accelerated warming, with a change in the temperature trend from 0.0016°C yr−1, between the early 1990s and 2005, to 0.0026°C yr−1 afterwards.

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“…Repeating earthquakes (repeaters) are events that recurrently rupture the same fault patch with the same focal mechanisms, often characterized by nearly identical waveforms (Abercrombie et al., 2020; Gao & Kao, 2020; Hatch et al., 2020; Sheng et al., 2021; Uchida & Bürgmann, 2019). These events are of great importance in many aspects of geophysics, such as monitoring subtle temporal changes of crustal properties (e.g., Pacheco et al., 2017; Poupinet et al., 1984; Sawazaki et al., 2015; Schaff & Beroza, 2004) and oceanic temperature (Wu et al., 2020), estimating fault creep (e.g., Materna et al., 2018; Matsubara et al., 2005; Nadeau & Johnson, 1998; Uchida et al., 2003, 2006; Yu, 2013), investigating inner core rotation (e.g., A. Li & Richards, 2003; Tkalčić et al., 2013; Zhang et al., 2005, 2008), evaluating the precision of earthquake locations (e.g., Jiang et al., 2014; A. Li & Richards, 2003; Meier et al., 2004; Schaff & Richards, 2011), and providing insights into the nucleation process of earthquakes (Huang & Meng, 2018; Kato & Nakagawa, 2014; Kato et al., 2012; Meng et al., 2015) and landslides (Yamada et al., 2016).…”

Section: Introductionmentioning

confidence: 99%

Misconception of Waveform Similarity in the Identification of Repeating Earthquakes

Gao

Kao

Wang

2021

Geophysical Research Letters

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Identification of repeating earthquakes (repeaters) usually depends on waveform similarity expressed as the corresponding cross‐correlation coefficient (CC) above a prescribed threshold, typically ranging in 0.70–0.98. However, the robustness and effectiveness of such a strategy have rarely been fully examined. In this study, we examine whether CC is a valid proxy for repeater identification through both synthetic and real earthquake experiments. We reveal that CC is controlled by not only the interevent distance but also many other factors, including station azimuth, epicentral distance, and velocity structure. Consequently, CC lacks the resolution in identifying true repeaters. For reliable repeater identification, we should consider the interevent overlap. Specifically, we define an event pair to be true repeaters if their interevent separation is smaller than the source dimension of the larger event. Our results imply that a systematic recheck of previously identified repeaters and associated interpretations/hypotheses may be important and necessary.

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Seismic ocean thermometry

Cited by 60 publications

References 58 publications

Noise Levels and Signals Observed on Submarine Fibers in the Canary Islands Using DAS

Noise Levels and Signals Observed on Submarine Fibers in the Canary Islands Using DAS

Warming Trend in Antarctic Bottom Water in the Vema Channel in the South Atlantic

Misconception of Waveform Similarity in the Identification of Repeating Earthquakes

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