Tracking Submarine Volcanic Activity at Monowai: Constraints From Long‐Range Hydroacoustic Measurements

Metz, Dirk; Watts, A. B.; Grevemeyer, Ingo; Rodgers, Mel

doi:10.1029/2018jb015888

Cited by 14 publications

(17 citation statements)

References 74 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the direct relation between the bathymetric slope and its spatial extent and the incidence angle of the signals is unclear. Metz et al (2018) indicated a systematic counterclockwise deviation of 0.4 • for the observed signal of the Monowai Seamount compared to the true geodesic angle of arrival. This deviation could partially be attributed to the indirect effect of the steep slope near H03S as indicated by array processing and cross-correlations.…”

Section: Discussionmentioning

confidence: 92%

A study on the ambient noise field at a hydroacoustic array near Robinson Crusoe Island

Sambell

Smets

Simons

et al. 2019

Geophysical Journal International

View full text Add to dashboard Cite

Continuous long-term sound sources are recorded at hydroacoustic station H03S, a threeelement hydrophone array south of Robinson Crusoe Island between 2014 April 23 and 2017 August 20. The origin of the signal between 3 and 20 Hz is investigated by using cross-correlation, array processing using plane wave beamforming and spectral analysis. Onebit normalization is successfully applied as a cross-correlation pre-processing step in order to suppress undesired earthquake events in the data. Traveltimes retrieved from averaged cross-correlations do not yield a coherent array direction of arrival. Averaged envelopes of the cross-correlations, however, indicate a coherent signal approaching H03S from a southsouthwest direction. Beamforming indicates two dominant backazimuth directions: 172 •-224 • (Antarctica) and 242 • (Monowai Volcanic Seamount). This continuous source field creates possibilities to investigate the applicability of acoustic thermometry at hydrophones H03 S1-S2. Cross-correlation and array processing indicate significant directional variation in local propagation, most likely related to the steep slope in the bathymetry near H03S. In addition, it is demonstrated that the ambient noise field is not sufficiently equipartitioned. It is shown that this causes a large error in the estimated temperature, primarily due to the short receiver spacing. These large errors have not been addressed in previous studies on deep-ocean acoustic thermometry. Hence, it is shown that acoustic thermometry does not perform well on small arrays such as H03S. The power spectral density yields a strong broadband signal in January-March, most likely related to iceberg noise. A narrow banded signal around 17 Hz between April and September corresponds to whale calls. The best-beam sound pressure levels towards Antarctica are compared to ERA5 climatologies for sea ice cover and normalized stress into the ocean, supporting the hypothesis of iceberg noise.

show abstract

Section: Discussionmentioning

confidence: 92%

A study on the ambient noise field at a hydroacoustic array near Robinson Crusoe Island

Sambell

Smets

Simons

et al. 2019

Geophysical Journal International

View full text Add to dashboard Cite

show abstract

“…Given a stationary and comparable source, the phase-velocity dispersion curve could be retrieved similar to Kästle et al (2016). Despite the clear modal signature in Figure 2b, the MVC is not a perfect stationary source with an identical signature for each event (e.g., Metz et al, 2018).…”

Section: Example Ccfmentioning

confidence: 97%

“…(2016). Despite the clear modal signature in Figure 2b, the MVC is not a perfect stationary source with an identical signature for each event (e.g., Metz et al., 2018).…”

Section: Cross‐correlation Functionsmentioning

confidence: 99%

“…Metz et al. (2018) have indicated a systematic back azimuth bias of −1.3° ± 0.2° for H03S, resolved by estimating the back azimuth of repetitive airgun shots near the coast of Chile.…”

Section: Instrumentationmentioning

confidence: 99%

“…Hence, back azimuth estimation using the planar wave propagation approximation can be carried out in the horizontal plane only. Metz et al (2018) have indicated a systematic back azimuth bias of −1.3° ± 0.2° for H03S, resolved by estimating the back azimuth of repetitive airgun shots near the coast of Chile.…”

Section: Hydrophone Tripletsmentioning

confidence: 99%

See 2 more Smart Citations

Hydroacoustic Travel Time Variations as a Proxy for Passive Deep‐Ocean Thermometry—A Cookbook

2022

View full text Add to dashboard Cite

We report on the extraction of deep ocean travel time variations from time‐lapse cross‐correlations between a hydrophone station and a three‐component broadband seismometer. The signals we cross‐correlate in this study result from repeated activity by the Monowai seamount, one of the most active submarine volcanoes of the Tonga‐Kermadec ridge. In particular, we introduce a specific workflow to exploit repetitive hydroacoustic underwater source activity, which we detail to such an extent that it serves as an example (or “cookbook”). For this reason, we have made the source code publicly available. The workflow proposed in this study (a) overcomes differences in instrument sensitivity and sample rates, (b) involves the selection of eligible cross‐correlations based on a source activity criterium as well as slowness analysis, and (c) extracts the travel time variations in distinct frequency bands. In our case, the two frequency bands are 3–6 and 6–12 Hz. We find that the estimated travel time variations in both frequency bands consist of a complex periodic pattern superimposed on a robust linear trend. This linear trend is decreasing, which we attribute to increasing water temperatures along the propagation path of the hydroacoustic signals.

show abstract

Natural and Anthropogenic Sources of Seismic, Hydroacoustic, and Infrasonic Waves: Waveforms and Spectral Characteristics (and Their Applicability for Sensor Calibration)

et al. 2022

View full text Add to dashboard Cite

The record of seismic, hydroacoustic, and infrasonic waves is essential to detect, identify, and localize sources of both natural and anthropogenic origin. To guarantee traceability and inter-station comparability, as well as an estimation of the measurement uncertainties leading to a better monitoring of natural disasters and environmental aspects, suitable measurement standards and reliable calibration procedures of sensors, especially in the low-frequency range down to 0.01 Hz, are required. Most of all with regard to the design goal of the Comprehensive Nuclear-Test-Ban Treaty Organisation’s International Monitoring System, which requires the stations to be operational nearly 100% of the time, the on-site calibration during operation is of special importance. The purpose of this paper is to identify suitable excitation sources and elaborate necessary requirements for on-site calibrations. We give an extensive literature review of a large variety of anthropogenic and natural sources of seismic, hydroacoustic, and infrasonic waves, describe their most prominent features regarding signal and spectral characteristics, explicitly highlight some source examples, and evaluate the reviewed sources with respect to requirements for on-site calibrations such as frequency bandwidth, signal properties as well as the applicability in terms of cost–benefit. According to our assessment, earthquakes stand out across all three waveform technologies as a good natural excitation signal meeting the majority of the requirements. Furthermore, microseisms and microbaroms allow a calibration at very low frequencies. We also find that in each waveform technique man-made controlled sources such as drop weights or air guns are in good agreement with the required properties, although limitations may arise regarding the practicability. Using these sources, procedures will be established allowing calibration without record interrupting, thereby improving data quality and the identification of treaty-related events.

show abstract

Tracking Submarine Volcanic Activity at Monowai: Constraints From Long‐Range Hydroacoustic Measurements

Cited by 14 publications

References 74 publications

A study on the ambient noise field at a hydroacoustic array near Robinson Crusoe Island

A study on the ambient noise field at a hydroacoustic array near Robinson Crusoe Island

Hydroacoustic Travel Time Variations as a Proxy for Passive Deep‐Ocean Thermometry—A Cookbook

Natural and Anthropogenic Sources of Seismic, Hydroacoustic, and Infrasonic Waves: Waveforms and Spectral Characteristics (and Their Applicability for Sensor Calibration)

Contact Info

Product

Resources

About