Distinguishing high surf from volcanic long‐period earthquakes

Lyons, J. J.; Haney, Matthew M.; Fee, David; Paskievitch, John F.

doi:10.1002/2013gl058954

Cited by 17 publications

(16 citation statements)

References 23 publications

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“…In this study, seismic data are band‐pass filtered from 3–12 Hz, which includes the primary frequency range of recorded activity. This frequency range also largely avoids local, long‐period events (<3 Hz) associated with concurrent, persistent, low‐level eruptive activity at Pagan volcano (Lyons et al, ) or surf noise (Lyons et al, ).…”

Section: Seismoacoustic Data and Methodsmentioning

confidence: 99%

Hydroacoustic, Seismic, and Bathymetric Observations of the 2014 Submarine Eruption at Ahyi Seamount, Mariana Arc

Tepp

Chadwick

Haney

et al. 2019

Geochem Geophys Geosyst

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Ahyi seamount, a shallow submarine volcano in the Northern Mariana Islands, began erupting on 23 April 2014. Hydroacoustic eruption signals were observed on the regional Mariana seismic network and on distant hydrophones, and National Oceanic and Atmospheric Administration (NOAA) scuba divers working in the area soon after the eruption began heard and felt underwater explosion sounds. The NOAA crew observed yellow‐orange bubble mats along the shore of neighboring Farallon de Pájaros Island, but no other surface manifestations of the eruption were reported by the crew or observed in satellite data. Here, we detail the eruption chronology and its morphologic impacts through analysis of seismic and hydroacoustic recordings and repeat bathymetric mapping. Throughout the 2‐week‐long eruption, Ahyi produced several thousand short, impulsive hydroacoustic signals that we interpret as underwater explosions as well as tremor near the beginning and end of the sequence. The initial tremor, which occurred for 2 hr, is interpreted as small phreatomagmatic explosions. This tremor was followed by a 90‐min pause before the characteristic impulsive signals began. Occasional tremor (lasting up to a few minutes) during the last 1.5 days of the eruption is interpreted as more sustained eruptive activity. Bathymetric changes show that a new crater, about 150 m deep, formed near the former summit and a large landslide chute formed on the southeastern flank. Comparing to other geophysically detected submarine eruptions, we find that the signals from the 2014 Ahyi eruption were more similar to those from other shallow or at‐surface submarine eruptions than those at deep (>500 m) eruptions.

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Section: Seismoacoustic Data and Methodsmentioning

confidence: 99%

Hydroacoustic, Seismic, and Bathymetric Observations of the 2014 Submarine Eruption at Ahyi Seamount, Mariana Arc

Tepp

Chadwick

Haney

et al. 2019

Geochem Geophys Geosyst

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“…Thus far, very little experimental data are available and its accuracy is insufficient because of the limitations and difficulties of experimental methods. As a result, current estimates of the lattice thermal conductivity of Earth's lower mantle largely rely on theoretical calculations [Hofmeister, 1999;Haigis et al, 2012;Dekura et al, 2013;Ammann et al, 2014;Tang et al, 2014;Stackhouse et al, 2015] or model extrapolations based on results at relatively low P-T conditions, without consideration of the potential effects of chemical composition at the lowermost mantle conditions. Recently, pulsed lasers coupled with high-pressure diamond anvil cell (DAC) have been applied to study the lattice thermal conductivity or diffusivity of deep-Earth materials under extreme conditions [Hsieh et al, 2009;Goncharov et al, 2010Goncharov et al, , 2015Ohta et al, 2012;Dalton et al, 2013;Konôpková et al, 2016].…”

Section: Introductionmentioning

confidence: 99%

Reduced lattice thermal conductivity of Fe‐bearing bridgmanite in Earth's deep mantle

et al. 2017

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Complex seismic, thermal, and chemical features have been reported in Earth's lowermost mantle. In particular, possible iron enrichments in the large low shear‐wave velocity provinces (LLSVPs) could influence thermal transport properties of the constituting minerals in this region, altering the lower mantle dynamics and heat flux across core‐mantle boundary (CMB). Thermal conductivity of bridgmanite is expected to partially control the thermal evolution and dynamics of Earth's lower mantle. Importantly, the pressure‐induced lattice distortion and iron spin and valence states in bridgmanite could affect its lattice thermal conductivity, but these effects remain largely unknown. Here we precisely measured the lattice thermal conductivity of Fe‐bearing bridgmanite to 120 GPa using optical pump‐probe spectroscopy. The conductivity of Fe‐bearing bridgmanite increases monotonically with pressure but drops significantly around 45 GPa due to pressure‐induced lattice distortion on iron sites. Our findings indicate that lattice thermal conductivity at lowermost mantle conditions is twice smaller than previously thought. The decrease in the thermal conductivity of bridgmanite in mid‐lower mantle and below would promote mantle flow against a potential viscosity barrier, facilitating slabs crossing over the 1000 km depth. Modeling of our results applied to LLSVPs shows that variations in iron and bridgmanite fractions induce a significant thermal conductivity decrease, which would enhance internal convective flow. Our CMB heat flux modeling indicates that while heat flux variations are dominated by thermal effects, variations in thermal conductivity also play a significant role. The CMB heat flux map we obtained is substantially different from those assumed so far, which may influence our understanding of the geodynamo.

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“…PGBF has a three‐component, Güralp 6TD intermediate band (0.033–50 Hz) seismometer and a six‐element, collocated infrasound array of VDP‐10 differential pressure transducers (Thelen & Cooper, ) with flat responses between 0.0125 and 25 Hz and a sensitivity of 10 mV/Pa. At the time of the explosion studied here, Pagan activity was dominated by continuous degassing from the summit vent that generated long‐period seismic events and very‐long‐period infrasound events (10–50 per hour); explosions were infrequent (Lyons et al, , ). The seismo‐acoustic energy from the explosion is peaked between 0.25 and 5 Hz with signals lasting 20–30 s. Acoustic amplitudes are ~1–2 Pa at ~3 km with seismic amplitudes at ~6 μm/s.…”

Section: Datamentioning

confidence: 97%

Infrasound Signal Detection and Back Azimuth Estimation Using Ground‐Coupled Airwaves on a Seismo‐Acoustic Sensor Pair

et al. 2018

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We present a new infrasonic signal detection and back azimuth determination technique that requires just one microphone and one three‐component seismometer. Ground‐coupled airwaves (GCAs) occur when an incident atmospheric acoustic wave impinges on the ground surface and is partially transmitted as a seismic wave. GCAs are commonly detected hundreds of kilometers away on seismic networks and are observed to have retrograde particle motion. Horizontally propagating acoustic waves and GCAs have previously been observed on collocated infrasound and seismic sensor pairs as coherent with a 90° phase difference. If the sensors are spatially separated, an additional propagation‐induced phase shift is present. The additional phase shift depends on the direction from which the acoustic wave arrives, as each back azimuth has a different apparent distance between the sensors. We use the additional phase shift, the coherence, and the characteristic particle motion on the three‐component seismometer to determine GCA arrivals and their unique back azimuth. We test this technique with synthetic seismo‐acoustic data generated by a coupled Earth‐atmosphere 3‐D finite difference code, as well as three seismo‐acoustic data sets from Mount St. Helens, Mount Cleveland, and Mount Pagan volcanoes. Results from our technique compare favorably with traditional infrasound array processing and provide robust GCA detection and back azimuth determination. Assuming adequate station spacing and sampling, our technique provides a new and robust method to detect infrasonic signals and determine their back azimuth, and may be of practical benefit where resources are limited and large sensor networks or arrays are not feasible.

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Distinguishing high surf from volcanic long‐period earthquakes

Cited by 17 publications

References 23 publications

Hydroacoustic, Seismic, and Bathymetric Observations of the 2014 Submarine Eruption at Ahyi Seamount, Mariana Arc

Hydroacoustic, Seismic, and Bathymetric Observations of the 2014 Submarine Eruption at Ahyi Seamount, Mariana Arc

Reduced lattice thermal conductivity of Fe‐bearing bridgmanite in Earth's deep mantle

Infrasound Signal Detection and Back Azimuth Estimation Using Ground‐Coupled Airwaves on a Seismo‐Acoustic Sensor Pair

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