Haruyoshi Matsumoto | Oregon State University (original) (raw)
Papers by Haruyoshi Matsumoto
Seismological Research Letters
Hydroacoustics has been successfully applied to detect and locate small-to-intermediate submarine... more Hydroacoustics has been successfully applied to detect and locate small-to-intermediate submarine tectonic activities infrequently recorded in land-based seismic arrays. However, to extend the utilization of T waves to extract other important earthquake source parameters, such as source strength, the roles of earthquake focal mechanisms, and source depths in T-wave envelopes must be thoroughly understood. We performed 3D numerical modeling considering anisotropic source radiation and realistic scattering in the oceanic crust for two focal mechanisms (normal and strike-slip faults) and three depths (5, 10, and 15 km) to investigate the effect of source radiation and focal depth on abyssal T waves. By analyzing the synthetic T-wave envelopes, we showed that stronger SV-energy radiation from a normal-fault earthquake event generates higher-intensity T waves of the same source magnitude. The anisotropic source radiation of a double-couple source causes azimuthal changes in the shapes of...
OCEANS 2019 MTS/IEEE SEATTLE, 2019
With ONR/DURIP funding (award # N00014-13-1-0345), we are currently developing the Long-term Acou... more With ONR/DURIP funding (award # N00014-13-1-0345), we are currently developing the Long-term Acoustic Real-Time Sensor for Polar Areas (LARA) which combines the advantages of both submerged and surface acoustic observing systems. LARA makes stationary passive acoustic monitoring efforts more effective, and provides maximum flexibility allowing for a wide range of applications even in ice-covered polar areas. While the ONR/DURIP award provides funding to design and manufacture the prototype unit, it doesn't cover expenses for field testing and performance evaluation. This new ONR award will allow us to conduct initial short-term deployments of LARA of the Newport, OR coast followed by a one-year deployment in the seasonally ice-covered northern Bering Sea, AK. Throughout the deployment we will closely monitor LARA remotely from Newport, OR and make changes to the firmware if necessary. After recovery a full data analysis and performance evaluation of the recorded acoustics and engineering data will be conducted. OBJECTIVES Most state-of-the-art passive acoustic monitoring systems are designed to stay submerged for the entire deployment period (for a summary see Mellinger et al., 2007). Deep-moored instruments feature a number of advantages. For example, they are not subject to the wear and tear caused by surface waves. However, with archival instruments it is not possible to access data, gain timely information on the presence of acoustic signals of interest (e.g., marine mammal vocalizations or seismic events), or identify system malfunctions prior to instrument recovery. Furthermore, it is not possible to update the system clock by GPS, which might drift significantly during long-term deployments and hinder accurate localization of sound sources when using multiple instruments (e.g., for tracking vocalizing
The Journal of the Acoustical Society of America, 2020
This package contains Matlab scripts and a partial dataset for spectral analysis and visualizatio... more This package contains Matlab scripts and a partial dataset for spectral analysis and visualization in Yun et al. (2021), "Quantifying soundscapes in the Ross Sea, Antarctica using long-term autonomous hydroacoustic monitoring systems" Front. Mar. Sci. Please refer to the "DATA AVAILABILITY STATEMENT" of the original paper(Yun et al., 2021) to get the entire dataset. No guarantee is given that the codes are running on another machine. Matlab version 2021a was used to run the code.
This earthquake catalog has 105756 records spanning the time range from 2009 Julian day: 022 to 2... more This earthquake catalog has 105756 records spanning the time range from 2009 Julian day: 022 to 2010 Julian day: 109. The events were located using phase arrival time data from networks of both moored hydrophones and Ocean-Bottom Seismometers. The data file is in ASCII format, with the following columns: Origin time Year, Julian Day, HR, MN, Sec, tenths Sec, Number stations, Station ID, lat, Long, laterr, Longerr, Origin Time error, Acoustic Magnitude (dB). The data file was generated as part of the projects called Assessment of T-wave Processes and Hydroacoustic Monitoring Capabilities in the Lau Basin, and Continuous acoustic and volcanic debris records of the deepest explosive submarine eruption ever observed. Funding was from NSF awards OCE08-25330, OCE08-25295, OCE08-25424, OCE10-29278, and from the NOAA/PMEL Vents Program.
OCEANS 2015 - MTS/IEEE Washington, 2015
Acoustic monitoring of cetaceans was conducted using two buoyancy-driven AUVs in a deep-water can... more Acoustic monitoring of cetaceans was conducted using two buoyancy-driven AUVs in a deep-water canyon north of the Navy's QUTR range off the Washington coast in April 2015. The two AUVs operated were the acoustically-equipped QUEphone, which is an APEX™-based acoustic profiler float from Teledyne Webb, and the Seaglider™ from Kongsberg. A passive acoustic monitoring device, WISPR, from Embedded Ocean Systems (EOS) was installed on both AUVs. With one 512-GB CF card and level-2 Free Lossless Audio Codec (FLAC), WISPR recorded sound continuously for 12 days at a 125 kHz sampling rate with 16-bit resolution. The Sealider's record showed high levels of flow noise below 100 Hz during ascent, 16 dB higher than during the descent. The Seaglider's CTD generated 1-sec long line noise at 53.37 kHz at 5 to 10 sec intervals, while the Seaglider's mass shifter generated 3-sec long band-limited noise below 10 kHz. The QUEphone's acoustic record was generally quieter than the Seaglider primarily due to the fact that it is nearly stationary platform with less mechanical and electrical components to generate system noise. Despite higher system noise levels, the Seaglider detected twice as many calls/clicks resulting from its ability to actively stay in the target area where the population density of marine mammals was higher, while the QUEphone drifted away from the target area with the prevailing ocean currents.
In December 2015, three hydrophones were moored at the east side of Drygalski Ice Tongue (DIT), s... more In December 2015, three hydrophones were moored at the east side of Drygalski Ice Tongue (DIT), seaward of the Nansen Ice Shelf (NIS). On 7 April 2016, the front of the NIS calved into two medium-sized icebergs, presenting a rare opportunity to measure the temporal variation of acoustic signals produced by a large scale ice shelf fracturing event. The acoustic data indicates there are hundreds of short duration, broadband (10–400 Hz) signals throughout the 4-month hydrophone record. We interpret these signals as cryogenic, caused by the cracking of the ice shelves and impacts of nearby sea-ice. The majority of these ice-cracking signals occur during the 21 January to 21 March time frame, two months to two weeks prior to the shelf fracturing observed by satellite on 7 April. Meteorological records of barometric pressure, air temperature, and wind speed show that the day the two icebergs drifted from the NIS coincided with the largest low pressure storm system recorded in the previous...
A year-long experiment to monitor underwater ambient noise measurements in shallow, (∼50m) open w... more A year-long experiment to monitor underwater ambient noise measurements in shallow, (∼50m) open water along an energetic coastline in the Pacific Northwest (USA) was conducted. Bottom mounted passive acoustic recorders were deployed in March 2010 by Oregon State University (OSU) and NOAA/Pacific Marine Environmental Laboratory's Marine Acoustics Research Group in an area designated by the Northwest National Marine Renewable Energy Center (NNMREC) as a mobile ocean test berth (MOTB) site for wave energy conversion (WEC) platforms off the central coast of Oregon. Acoustic recording packages recorded continuous (1 Hz–2 kHz) sampling at two offshore locations near and within the MOTB. Maximum and minimum total sound pressure levels recorded during the experiment reached 136 dB re 1 µPa and 95 dB re 1 µPa respectively. Meanwhile, the time averaged sound pressure levels for the year long deployment were 113 dB re 1µPa. These data provide the initial baseline recordings required for a ...
PloS one, 2015
Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Penins... more Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10-20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifi...
PloS one, 2015
Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Penins... more Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10-20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifi...
Conference Proceedings on Engineering in the Ocean Environment
ABSTRACT Not Available
Geochemistry, Geophysics, Geosystems, 2014
In late 2007, two massive icebergs, C19a and B15a, drifted into open water and slowly disintegrat... more In late 2007, two massive icebergs, C19a and B15a, drifted into open water and slowly disintegrated in the southernmost Pacific Ocean. Archived acoustic records show that the high-intensity underwater sounds accompanying this breakup increased ocean noise levels at mid-to-equatorial latitudes over a period of 1.5 years. More typically, seasonal variations in ocean noise, which are characterized by austral summer-highs and winter-lows, appear to be modulated by the annual cycle of Antarctic iceberg drift and subsequent disintegration. This seasonal pattern is observed in all three Oceans of the Southern Hemisphere. The life cycle of Antarctic icebergs affects not only marine ecosystem but also the sound environment in far-reaching areas and must be accounted for in any effort to isolate anthropogenic or climateinduced noise contributions to the ocean soundscape.
Nature Geoscience, 2012
Volcanoes at spreading centres on land often exhibit seismicity and ground inflation months to ye... more Volcanoes at spreading centres on land often exhibit seismicity and ground inflation months to years before an eruption, caused by a gradual influx of magma to the source reservoir 1-4. Deflation and seismicity can occur on time scales of hours to days, and result from the injection of magma into adjacent rift zones 5-8. Volcanoes at submarine rift zones, such as Axial Seamount in the northeast Pacific Ocean, have exhibited similar behaviour 9-12 , but a direct link between seismicity, seafloor deformation and magma intrusion has never been demonstrated. Here we present recordings from ocean-bottom hydrophones and an established array of bottom-pressure recorders that reveal patterns of both microearthquakes and seafloor deformation at Axial Seamount on the Juan de Fuca Ridge, before it erupted in April 2011. Our observations show that the rate of seismicity increased steadily during a period of several years, leading up to an intrusion and eruption of magma that began on 6 April 2011. We also detected a sudden increase in seismo-acoustic energy about 2.6 h before the eruption began. Our data indicate that access to real-time seismic data, projected to be available in the near future, might facilitate short-term forecasting and provide sufficient leadtime to prepare in situ instrumentation before future intrusion and eruption events. Since late 2006, up to four ocean bottom hydrophones (OBHs) have been deployed at Axial Seamount, one within the caldera, two on the east and west caldera rims and one on the upper south rift zone (Fig. 1). The in situ hydrophones were deployed to detect microearthquake activity once it became clear the caldera was re-inflating 13 , but no regional earthquakes were being detected on the US Navy real-time hydrophone arrays that monitor the area and detected the 1998 eruption 12,14. The OBH array complements a ten-year effort to measure volcanic inflation within the caldera with multiyear deployments of continuously recording bottom pressure recorders 15 (BPRs). These pressure data are the only documented measurements of an inflation/deflation cycle at a submarine volcano 16. Analogous volcanic centres on land typically exhibit repeated cycles of ground inflation and seismic activity. Inflation periods lasting months to years track the influx of magma and accompanying increase in pressure within the shallow crustal reservoir 1-4. When this pressure is sufficient to initiate a diking event, magma is transported laterally along the rift zone and possibly erupted at the surface 2,4-6,8. Individual diking events are commonly short-lived (hours to days) and marked by ground deformation and migrating
The Journal of the Acoustical Society of America, 2011
An underwater glider with an acoustic data logger flew toward a recently discovered erupting subm... more An underwater glider with an acoustic data logger flew toward a recently discovered erupting submarine volcano in the northern Lau basin. With the volcano providing a wide-band sound source, recordings from the two-day survey produced a two-dimensional sound level map spanning 1 km (depth) Â 40 km (distance). The observed sound field shows depth-and range-dependence, with the first-order spatial pattern being consistent with the predictions of a range-dependent propagation model. The results allow constraining the acoustic source level of the volcanic activity and suggest that the glider provides an effective platform for monitoring natural and anthropogenic ocean sounds.
Journal of Geophysical Research, 2004
Mid-ocean ridge volcanic activity is the fundamental process for creation of ocean crust, yet the... more Mid-ocean ridge volcanic activity is the fundamental process for creation of ocean crust, yet the dynamics of magma emplacement along the slow spreading Mid-Atlantic Ridge (MAR) are largely unknown. We present acoustical, seismological, and biological evidence of a magmatic dike intrusion at the Lucky Strike segment, the first detected from the deeper sections (>1500 m) of the MAR. The dike caused the largest teleseismic earthquake swarm recorded at Lucky Strike in >20 years of seismic monitoring, and one of the largest ever recorded on the northern MAR. Hydrophone records indicate that the rate of earthquake activity decays in a nontectonic manner and that the onset of the swarm was accompanied by 30 min of broadband (>3 Hz) intrusion tremor, suggesting a volcanic origin. Two submersible investigations of high-temperature vents located at the summit of Lucky Strike Seamount 3 months and 1 year after the swarm showed a significant increase in microbial activity and diffuse venting. This magmatic episode may represent one form of volcanism along the MAR, where highly focused pockets of magma are intruded sporadically into the shallow ocean crust beneath long-lived, discrete volcanic structures recharging preexisting seafloor hydrothermal vents and ecosystems.
Geophysical Research Letters, 2002
In February 1999, long-term hydroacoustic monitoring of the northern Mid-Atlantic Ridge (MAR) was... more In February 1999, long-term hydroacoustic monitoring of the northern Mid-Atlantic Ridge (MAR) was initiated. Six autonomous hydrophones were moored between 15°Nand15°N and 15°Nand35°N on the flanks of the MAR. Results from the first year of data reveal that there is significant variability in along-axis event rate. Groups of neighboring segments behave similarly, producing an along-axis pattern with high and low levels of seismic activity at a wavelength of $500 km. This broad scale pattern is likely influenced by the axial thermal regime. Several earthquake sequences with variable temporal characteristics were detected, suggesting fundamental differences in the cause of their seismicity. Off-axis, most seismic faulting occurs within a zone <15 km from the axis center.
Geophysical Journal International, 2013
Using a short-baseline hydrophone array, persistent volcanoacoustic sources are identified within... more Using a short-baseline hydrophone array, persistent volcanoacoustic sources are identified within the ambient noise field of the Lau Basin during the period between 2009 January and 2010 April. The submarine volcano West Mata and adjacent volcanic terrains, including the northern Matas and Volcano O, are the most active acoustic sources during the 15-month period of observation. Other areas of long-term activity include the Niua hydrothermal field, the volcanic islands of Hunga Ha'apai, Founalei, Niuatoputapu and Niuafo'ou, two seamounts located along the southern Tofua Arc and at least three unknown sites within the northern Lau Basin. Following the great Samoan earthquake on 2009 September 29, seven of the volcanoacoustic sources identified exhibit increases in the rate of acoustic detection. These changes persist over timescales of days-to-months and are observed up to 900 km from the earthquake hypocentre. At least one of the volcanoacoustic sources that did not respond to the 2009 Samoan earthquake exhibits an increase in detection rate following the great Mw 8.8 Chile earthquake that occurred at a distance of ∼9500 km on 2010 February 27. These observations suggest that great earthquakes may have undocumented impacts on Earth's vast submarine volcanic systems, potentially increasing the short-term flux of magma and volcanic gas into the overlying ocean.
Geochemistry, Geophysics, Geosystems, 2012
The output of gas and tephra from volcanoes is an inherently disorganized process that makes reli... more The output of gas and tephra from volcanoes is an inherently disorganized process that makes reliable flux estimates challenging to obtain. Continuous monitoring of gas flux has been achieved in only a few instances at subaerial volcanoes, but never for submarine volcanoes. Here we use the first sustained (yearlong) hydroacoustic monitoring of an erupting submarine volcano (NW Rota-1, Mariana arc) to make calculations of explosive gas flux from a volcano into the ocean. Bursts of Strombolian explosive degassing at the volcano summit (520 m deep) occurred at 1-2 min intervals during the entire 12-month hydrophone record and commonly exhibited cyclic step-function changes between high and low intensity. Total gas flux calculated from the hydroacoustic record is 5.4 AE 0.6 Tg a À1 , where the magmatic gases driving eruptions at NW Rota-1 are primarily H 2 O, SO 2 , and CO 2. Instantaneous fluxes varied by a factor of 100overthedeployment.UsingmeltinclusioninformationtoestimatetheconcentrationofCO2intheexplosivegasesas6.9AE0.7wt100 over the deployment. Using melt inclusion information to estimate the concentration of CO 2 in the explosive gases as 6.9 AE 0.7 wt %, we calculate an annual CO 2 eruption flux of 0.4 AE 0.1 Tg a À1. This result is within the range of measured CO 2 fluxes at continuously erupting subaerial volcanoes, and represents 100overthedeployment.UsingmeltinclusioninformationtoestimatetheconcentrationofCO2intheexplosivegasesas6.9AE0.7wt0.2-0.6% of the annual estimated output of CO 2 from all subaerial arc volcanoes, and $0.4-0.6% of the mid-ocean ridge flux. The multiyear eruptive history of NW Rota-1 demonstrates that submarine volcanoes can be significant and sustained sources of CO 2 to the shallow ocean.
Seismological Research Letters
Hydroacoustics has been successfully applied to detect and locate small-to-intermediate submarine... more Hydroacoustics has been successfully applied to detect and locate small-to-intermediate submarine tectonic activities infrequently recorded in land-based seismic arrays. However, to extend the utilization of T waves to extract other important earthquake source parameters, such as source strength, the roles of earthquake focal mechanisms, and source depths in T-wave envelopes must be thoroughly understood. We performed 3D numerical modeling considering anisotropic source radiation and realistic scattering in the oceanic crust for two focal mechanisms (normal and strike-slip faults) and three depths (5, 10, and 15 km) to investigate the effect of source radiation and focal depth on abyssal T waves. By analyzing the synthetic T-wave envelopes, we showed that stronger SV-energy radiation from a normal-fault earthquake event generates higher-intensity T waves of the same source magnitude. The anisotropic source radiation of a double-couple source causes azimuthal changes in the shapes of...
OCEANS 2019 MTS/IEEE SEATTLE, 2019
With ONR/DURIP funding (award # N00014-13-1-0345), we are currently developing the Long-term Acou... more With ONR/DURIP funding (award # N00014-13-1-0345), we are currently developing the Long-term Acoustic Real-Time Sensor for Polar Areas (LARA) which combines the advantages of both submerged and surface acoustic observing systems. LARA makes stationary passive acoustic monitoring efforts more effective, and provides maximum flexibility allowing for a wide range of applications even in ice-covered polar areas. While the ONR/DURIP award provides funding to design and manufacture the prototype unit, it doesn't cover expenses for field testing and performance evaluation. This new ONR award will allow us to conduct initial short-term deployments of LARA of the Newport, OR coast followed by a one-year deployment in the seasonally ice-covered northern Bering Sea, AK. Throughout the deployment we will closely monitor LARA remotely from Newport, OR and make changes to the firmware if necessary. After recovery a full data analysis and performance evaluation of the recorded acoustics and engineering data will be conducted. OBJECTIVES Most state-of-the-art passive acoustic monitoring systems are designed to stay submerged for the entire deployment period (for a summary see Mellinger et al., 2007). Deep-moored instruments feature a number of advantages. For example, they are not subject to the wear and tear caused by surface waves. However, with archival instruments it is not possible to access data, gain timely information on the presence of acoustic signals of interest (e.g., marine mammal vocalizations or seismic events), or identify system malfunctions prior to instrument recovery. Furthermore, it is not possible to update the system clock by GPS, which might drift significantly during long-term deployments and hinder accurate localization of sound sources when using multiple instruments (e.g., for tracking vocalizing
The Journal of the Acoustical Society of America, 2020
This package contains Matlab scripts and a partial dataset for spectral analysis and visualizatio... more This package contains Matlab scripts and a partial dataset for spectral analysis and visualization in Yun et al. (2021), "Quantifying soundscapes in the Ross Sea, Antarctica using long-term autonomous hydroacoustic monitoring systems" Front. Mar. Sci. Please refer to the "DATA AVAILABILITY STATEMENT" of the original paper(Yun et al., 2021) to get the entire dataset. No guarantee is given that the codes are running on another machine. Matlab version 2021a was used to run the code.
This earthquake catalog has 105756 records spanning the time range from 2009 Julian day: 022 to 2... more This earthquake catalog has 105756 records spanning the time range from 2009 Julian day: 022 to 2010 Julian day: 109. The events were located using phase arrival time data from networks of both moored hydrophones and Ocean-Bottom Seismometers. The data file is in ASCII format, with the following columns: Origin time Year, Julian Day, HR, MN, Sec, tenths Sec, Number stations, Station ID, lat, Long, laterr, Longerr, Origin Time error, Acoustic Magnitude (dB). The data file was generated as part of the projects called Assessment of T-wave Processes and Hydroacoustic Monitoring Capabilities in the Lau Basin, and Continuous acoustic and volcanic debris records of the deepest explosive submarine eruption ever observed. Funding was from NSF awards OCE08-25330, OCE08-25295, OCE08-25424, OCE10-29278, and from the NOAA/PMEL Vents Program.
OCEANS 2015 - MTS/IEEE Washington, 2015
Acoustic monitoring of cetaceans was conducted using two buoyancy-driven AUVs in a deep-water can... more Acoustic monitoring of cetaceans was conducted using two buoyancy-driven AUVs in a deep-water canyon north of the Navy's QUTR range off the Washington coast in April 2015. The two AUVs operated were the acoustically-equipped QUEphone, which is an APEX™-based acoustic profiler float from Teledyne Webb, and the Seaglider™ from Kongsberg. A passive acoustic monitoring device, WISPR, from Embedded Ocean Systems (EOS) was installed on both AUVs. With one 512-GB CF card and level-2 Free Lossless Audio Codec (FLAC), WISPR recorded sound continuously for 12 days at a 125 kHz sampling rate with 16-bit resolution. The Sealider's record showed high levels of flow noise below 100 Hz during ascent, 16 dB higher than during the descent. The Seaglider's CTD generated 1-sec long line noise at 53.37 kHz at 5 to 10 sec intervals, while the Seaglider's mass shifter generated 3-sec long band-limited noise below 10 kHz. The QUEphone's acoustic record was generally quieter than the Seaglider primarily due to the fact that it is nearly stationary platform with less mechanical and electrical components to generate system noise. Despite higher system noise levels, the Seaglider detected twice as many calls/clicks resulting from its ability to actively stay in the target area where the population density of marine mammals was higher, while the QUEphone drifted away from the target area with the prevailing ocean currents.
In December 2015, three hydrophones were moored at the east side of Drygalski Ice Tongue (DIT), s... more In December 2015, three hydrophones were moored at the east side of Drygalski Ice Tongue (DIT), seaward of the Nansen Ice Shelf (NIS). On 7 April 2016, the front of the NIS calved into two medium-sized icebergs, presenting a rare opportunity to measure the temporal variation of acoustic signals produced by a large scale ice shelf fracturing event. The acoustic data indicates there are hundreds of short duration, broadband (10–400 Hz) signals throughout the 4-month hydrophone record. We interpret these signals as cryogenic, caused by the cracking of the ice shelves and impacts of nearby sea-ice. The majority of these ice-cracking signals occur during the 21 January to 21 March time frame, two months to two weeks prior to the shelf fracturing observed by satellite on 7 April. Meteorological records of barometric pressure, air temperature, and wind speed show that the day the two icebergs drifted from the NIS coincided with the largest low pressure storm system recorded in the previous...
A year-long experiment to monitor underwater ambient noise measurements in shallow, (∼50m) open w... more A year-long experiment to monitor underwater ambient noise measurements in shallow, (∼50m) open water along an energetic coastline in the Pacific Northwest (USA) was conducted. Bottom mounted passive acoustic recorders were deployed in March 2010 by Oregon State University (OSU) and NOAA/Pacific Marine Environmental Laboratory's Marine Acoustics Research Group in an area designated by the Northwest National Marine Renewable Energy Center (NNMREC) as a mobile ocean test berth (MOTB) site for wave energy conversion (WEC) platforms off the central coast of Oregon. Acoustic recording packages recorded continuous (1 Hz–2 kHz) sampling at two offshore locations near and within the MOTB. Maximum and minimum total sound pressure levels recorded during the experiment reached 136 dB re 1 µPa and 95 dB re 1 µPa respectively. Meanwhile, the time averaged sound pressure levels for the year long deployment were 113 dB re 1µPa. These data provide the initial baseline recordings required for a ...
PloS one, 2015
Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Penins... more Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10-20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifi...
PloS one, 2015
Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Penins... more Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10-20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifi...
Conference Proceedings on Engineering in the Ocean Environment
ABSTRACT Not Available
Geochemistry, Geophysics, Geosystems, 2014
In late 2007, two massive icebergs, C19a and B15a, drifted into open water and slowly disintegrat... more In late 2007, two massive icebergs, C19a and B15a, drifted into open water and slowly disintegrated in the southernmost Pacific Ocean. Archived acoustic records show that the high-intensity underwater sounds accompanying this breakup increased ocean noise levels at mid-to-equatorial latitudes over a period of 1.5 years. More typically, seasonal variations in ocean noise, which are characterized by austral summer-highs and winter-lows, appear to be modulated by the annual cycle of Antarctic iceberg drift and subsequent disintegration. This seasonal pattern is observed in all three Oceans of the Southern Hemisphere. The life cycle of Antarctic icebergs affects not only marine ecosystem but also the sound environment in far-reaching areas and must be accounted for in any effort to isolate anthropogenic or climateinduced noise contributions to the ocean soundscape.
Nature Geoscience, 2012
Volcanoes at spreading centres on land often exhibit seismicity and ground inflation months to ye... more Volcanoes at spreading centres on land often exhibit seismicity and ground inflation months to years before an eruption, caused by a gradual influx of magma to the source reservoir 1-4. Deflation and seismicity can occur on time scales of hours to days, and result from the injection of magma into adjacent rift zones 5-8. Volcanoes at submarine rift zones, such as Axial Seamount in the northeast Pacific Ocean, have exhibited similar behaviour 9-12 , but a direct link between seismicity, seafloor deformation and magma intrusion has never been demonstrated. Here we present recordings from ocean-bottom hydrophones and an established array of bottom-pressure recorders that reveal patterns of both microearthquakes and seafloor deformation at Axial Seamount on the Juan de Fuca Ridge, before it erupted in April 2011. Our observations show that the rate of seismicity increased steadily during a period of several years, leading up to an intrusion and eruption of magma that began on 6 April 2011. We also detected a sudden increase in seismo-acoustic energy about 2.6 h before the eruption began. Our data indicate that access to real-time seismic data, projected to be available in the near future, might facilitate short-term forecasting and provide sufficient leadtime to prepare in situ instrumentation before future intrusion and eruption events. Since late 2006, up to four ocean bottom hydrophones (OBHs) have been deployed at Axial Seamount, one within the caldera, two on the east and west caldera rims and one on the upper south rift zone (Fig. 1). The in situ hydrophones were deployed to detect microearthquake activity once it became clear the caldera was re-inflating 13 , but no regional earthquakes were being detected on the US Navy real-time hydrophone arrays that monitor the area and detected the 1998 eruption 12,14. The OBH array complements a ten-year effort to measure volcanic inflation within the caldera with multiyear deployments of continuously recording bottom pressure recorders 15 (BPRs). These pressure data are the only documented measurements of an inflation/deflation cycle at a submarine volcano 16. Analogous volcanic centres on land typically exhibit repeated cycles of ground inflation and seismic activity. Inflation periods lasting months to years track the influx of magma and accompanying increase in pressure within the shallow crustal reservoir 1-4. When this pressure is sufficient to initiate a diking event, magma is transported laterally along the rift zone and possibly erupted at the surface 2,4-6,8. Individual diking events are commonly short-lived (hours to days) and marked by ground deformation and migrating
The Journal of the Acoustical Society of America, 2011
An underwater glider with an acoustic data logger flew toward a recently discovered erupting subm... more An underwater glider with an acoustic data logger flew toward a recently discovered erupting submarine volcano in the northern Lau basin. With the volcano providing a wide-band sound source, recordings from the two-day survey produced a two-dimensional sound level map spanning 1 km (depth) Â 40 km (distance). The observed sound field shows depth-and range-dependence, with the first-order spatial pattern being consistent with the predictions of a range-dependent propagation model. The results allow constraining the acoustic source level of the volcanic activity and suggest that the glider provides an effective platform for monitoring natural and anthropogenic ocean sounds.
Journal of Geophysical Research, 2004
Mid-ocean ridge volcanic activity is the fundamental process for creation of ocean crust, yet the... more Mid-ocean ridge volcanic activity is the fundamental process for creation of ocean crust, yet the dynamics of magma emplacement along the slow spreading Mid-Atlantic Ridge (MAR) are largely unknown. We present acoustical, seismological, and biological evidence of a magmatic dike intrusion at the Lucky Strike segment, the first detected from the deeper sections (>1500 m) of the MAR. The dike caused the largest teleseismic earthquake swarm recorded at Lucky Strike in >20 years of seismic monitoring, and one of the largest ever recorded on the northern MAR. Hydrophone records indicate that the rate of earthquake activity decays in a nontectonic manner and that the onset of the swarm was accompanied by 30 min of broadband (>3 Hz) intrusion tremor, suggesting a volcanic origin. Two submersible investigations of high-temperature vents located at the summit of Lucky Strike Seamount 3 months and 1 year after the swarm showed a significant increase in microbial activity and diffuse venting. This magmatic episode may represent one form of volcanism along the MAR, where highly focused pockets of magma are intruded sporadically into the shallow ocean crust beneath long-lived, discrete volcanic structures recharging preexisting seafloor hydrothermal vents and ecosystems.
Geophysical Research Letters, 2002
In February 1999, long-term hydroacoustic monitoring of the northern Mid-Atlantic Ridge (MAR) was... more In February 1999, long-term hydroacoustic monitoring of the northern Mid-Atlantic Ridge (MAR) was initiated. Six autonomous hydrophones were moored between 15°Nand15°N and 15°Nand35°N on the flanks of the MAR. Results from the first year of data reveal that there is significant variability in along-axis event rate. Groups of neighboring segments behave similarly, producing an along-axis pattern with high and low levels of seismic activity at a wavelength of $500 km. This broad scale pattern is likely influenced by the axial thermal regime. Several earthquake sequences with variable temporal characteristics were detected, suggesting fundamental differences in the cause of their seismicity. Off-axis, most seismic faulting occurs within a zone <15 km from the axis center.
Geophysical Journal International, 2013
Using a short-baseline hydrophone array, persistent volcanoacoustic sources are identified within... more Using a short-baseline hydrophone array, persistent volcanoacoustic sources are identified within the ambient noise field of the Lau Basin during the period between 2009 January and 2010 April. The submarine volcano West Mata and adjacent volcanic terrains, including the northern Matas and Volcano O, are the most active acoustic sources during the 15-month period of observation. Other areas of long-term activity include the Niua hydrothermal field, the volcanic islands of Hunga Ha'apai, Founalei, Niuatoputapu and Niuafo'ou, two seamounts located along the southern Tofua Arc and at least three unknown sites within the northern Lau Basin. Following the great Samoan earthquake on 2009 September 29, seven of the volcanoacoustic sources identified exhibit increases in the rate of acoustic detection. These changes persist over timescales of days-to-months and are observed up to 900 km from the earthquake hypocentre. At least one of the volcanoacoustic sources that did not respond to the 2009 Samoan earthquake exhibits an increase in detection rate following the great Mw 8.8 Chile earthquake that occurred at a distance of ∼9500 km on 2010 February 27. These observations suggest that great earthquakes may have undocumented impacts on Earth's vast submarine volcanic systems, potentially increasing the short-term flux of magma and volcanic gas into the overlying ocean.
Geochemistry, Geophysics, Geosystems, 2012
The output of gas and tephra from volcanoes is an inherently disorganized process that makes reli... more The output of gas and tephra from volcanoes is an inherently disorganized process that makes reliable flux estimates challenging to obtain. Continuous monitoring of gas flux has been achieved in only a few instances at subaerial volcanoes, but never for submarine volcanoes. Here we use the first sustained (yearlong) hydroacoustic monitoring of an erupting submarine volcano (NW Rota-1, Mariana arc) to make calculations of explosive gas flux from a volcano into the ocean. Bursts of Strombolian explosive degassing at the volcano summit (520 m deep) occurred at 1-2 min intervals during the entire 12-month hydrophone record and commonly exhibited cyclic step-function changes between high and low intensity. Total gas flux calculated from the hydroacoustic record is 5.4 AE 0.6 Tg a À1 , where the magmatic gases driving eruptions at NW Rota-1 are primarily H 2 O, SO 2 , and CO 2. Instantaneous fluxes varied by a factor of 100overthedeployment.UsingmeltinclusioninformationtoestimatetheconcentrationofCO2intheexplosivegasesas6.9AE0.7wt100 over the deployment. Using melt inclusion information to estimate the concentration of CO 2 in the explosive gases as 6.9 AE 0.7 wt %, we calculate an annual CO 2 eruption flux of 0.4 AE 0.1 Tg a À1. This result is within the range of measured CO 2 fluxes at continuously erupting subaerial volcanoes, and represents 100overthedeployment.UsingmeltinclusioninformationtoestimatetheconcentrationofCO2intheexplosivegasesas6.9AE0.7wt0.2-0.6% of the annual estimated output of CO 2 from all subaerial arc volcanoes, and $0.4-0.6% of the mid-ocean ridge flux. The multiyear eruptive history of NW Rota-1 demonstrates that submarine volcanoes can be significant and sustained sources of CO 2 to the shallow ocean.