Seismic detection of underwater volcanism: The example of French Polynesia

Talandier, Jacques; Okal, Emile A.

doi:10.1007/bf00879361

Cited by 64 publications

(36 citation statements)

References 50 publications

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“…log N = a-bM, where N is the number of earthquakes of magnitudeM or greater, and a and b are constants) is 1.09 ± 0.04 for the swarm. This is similar to the value of b = 0.98± 0.14 detennined by Talandier & Okal (1987) using T-phase recordings of events of the swarm, and is close to the worldwide average for earthquakes (b = 0.9), suggesting the swarm is largely oftectonic origin. Documented subaerial volcanic swarms have featured higher b-values, ranging from 1.4 to more than 3.…”

Section: Shallow Earthquakes North Islandsupporting

confidence: 66%

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New Zealand seismicity 1964–87: An interpretation

Reyners¹

1989

New Zealand Journal of Geology and Geophysics

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The years 1964-87 represent a relatively quiet period in the historical record of large earthquakes in New Zealand. Nevertheless, over 7000 earthquakes of magnitude M L ~ 4.0 were located with the National Seismograph Network during this period, and these provide important infonnation on the structure and tectonics of the country. Events deeper than 40 km reveal the morphology of the subducted plates in Fiordland and at the Hikurangi Margin. When combined with microearthquake results in the central South Island, these deeper earthquakes suggest that plate convergence is accommodated along a common northeasterly trend throughout New Zealand. Variations in the slope of the deeper limit of seismicity and in the depth of maximum earthquake activity in the dipping seismic zone at the Hikurangi Margin provide evidence for lateral segmentation of the subductcd plate.Earthquakes shallower than 40 km lack a clear association with major late Quaternary fault traces. However, the distribution of some of these events can be related to the large

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Section: Shallow Earthquakes North Islandsupporting

confidence: 66%

“…During the swarm, several earthquakes also occurred in the region of the 1974 swarm, including one event of ML = 5.2. Talandier & Okal (1987) have suggested that it is likely an episode of active volcanism took place during or before the 1984-85 swarm. However, the evidence for this is not compelling.…”

Section: Shallow Earthquakes North Islandmentioning

confidence: 99%

New Zealand seismicity 1964–87: An interpretation

Reyners¹

1989

New Zealand Journal of Geology and Geophysics

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“…It has long been known that episodes of underwater volcanic activity feature explosive events often interpreted as the release of magmatic conduits opening the way for the eruption of lava into the ocean (TALANDIER and OKAL, 1987a). In particular, such events were observed systematically at the beginning of swarms at Macdonald Seamount (TALANDIER and OKAL, 1982).…”

Section: Volcanoseismic Explosions (V)mentioning

confidence: 98%

Identification Criteria for Sources of T Waves Recorded in French Polynesia

Talandier

Okal

2001

Pure appl. geophys.

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Ð From a data set of 150 digital records of T phases from 71 sources obtained on seismometers of the Polynesian Seismic Network, we de®ne a discriminant separating earthquake and explosion sources, which uses the maximum amplitude of recorded ground velocity, measured on its envelope, e Max (in lm/s), and the duration of the phase measured at 1/3 of maximum amplitude, s 1=3 (in seconds). Earthquake sources and man-made explosions are eectively separated in a log-log space by the straight line log 10 e Max 4:9 log 10 s 1=3 À 4:1 :Other criteria in both the time and frequency domains fail to reliably separate the populations of the various kinds of events. The application of this technique to analog records of large-scale man-made explosions carried out in the 1960s con®rms that it provides an adequate discriminant over 3.5 orders of magnitude of ground velocity.

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“…Most relevant to this study are observations of tremor originating from submarine volcanic and hydrothermal systems in the deep ocean. Acoustic signals with harmonic characteristics have been detected at far regional distances by moored underwater hydrophones and island‐based seismic stations [e.g., Talandier and Okal , 1987; Dziak and Fox , 2002; Haxel and Dziak , 2005]. These tremor signals appear to be sourced from shallow (<800 m) volcanic seamounts, where sound may couple into and propagate efficiently within the ocean's low‐velocity waveguide.…”

Section: Introductionmentioning

confidence: 99%

Seismic tremor at the 9°50′N East Pacific Rise eruption site

Monigle

Bohnenstiehl

Tolstoy

et al. 2009

Geochem Geophys Geosyst

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[1] Ocean bottom seismic observations within the 9°50 0 N region of the East Pacific Rise indicate persistent, low-amplitude tremor activity throughout the October 2003 through February 2007 period of monitoring. These signals exhibit either monochromatic or polychromatic spectral characteristics, with a $6 Hz fundamental frequency and up to two harmonics. Individual events cannot be correlated between nearby (<1 km) stations, implying the presence of multiple, small-amplitude sources positioned within the shallow crust. Tremor exhibits a semidiurnal periodicity, with some stations recording activity during times of increasing tidal extension and others detecting tremor signals during times of increasing compression. The amplitude, duration, and rate of activity also correlate positively with fortnightly changes in the amplitude of the tides. These spatiotemporal patterns are consistent with tremor generation in response to tidally modulated fluid flow within a network of shallow cracks. Tremor energy flux is spatially and temporally heterogeneous; however, there are extended periods of greater and lesser activity that can be tracked across portions of the array. Despite their shallow crustal origin, changes in tremor amplitude and spectral character occur in the months prior to a major microearthquake swarm and inferred seafloor spreading event on 22 January 2006, with an increase in the degree of correlation between tremor activity and tidal strain in the weeks leading up to this event. After the spreading event, two eruption-surviving stations near the axis continue to show high rates of tremor activity, whereas these signals are suppressed at the single station recovered from the near-axis flanks. This off-axis quiescence may result from the dikeinduced closing of cracks or perhaps from the emplacement of impermeable flows near the station.

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Seismic detection of underwater volcanism: The example of French Polynesia

Cited by 64 publications

References 50 publications

New Zealand seismicity 1964–87: An interpretation

New Zealand seismicity 1964–87: An interpretation

Identification Criteria for Sources of T Waves Recorded in French Polynesia

Seismic tremor at the 9°50′N East Pacific Rise eruption site

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