K. A. Macpherson

University of Alaska Fairbanks

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Emma M. Hill

University of British Columbia

David Fee

University of Alaska Fairbanks

Paramesh Banerjee

Earth Observatory of Singapore

P. Elósegui

Massachusetts Institute of Technology

N. A. Ruppert

University of Alaska Fairbanks

Qiang Qiu

South China Sea Institute Of Oceanology

Alex J. C. Witsil

Applied Research Associates (United States)

Kerry Sieh

Nanyang Technological University

J. C. Borrero

eCoast (New Zealand)

Hermann M. Fritz

Georgia Institute of Technology

Cooperative Institutions

University of Alaska Fairbanks

Nanyang Technological University

National Tsunami Warning Center

Earth Observatory of Singapore

Centre National de la Recherche Scientifique

United States Geological Survey

Alaska Volcano Observatory

California Institute of Technology

CEA DAM Île-de-France

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

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Ambient Infrasound Noise, Station Performance, and Their Relation to Land Cover across Alaska

Seismological Research Letters (2022)

K. A. Macpherson Juliann R. Colwell Alex J. C. Witsil David Fee S. G. Holtkamp

Abstract The addition of 108 infrasound sensors—a legacy of the temporary USArray Transportable Array (TA) deployment—to the Alaska regional network provides an unprecedented opportunity to quantify the effects of a diverse set of site conditions on ambient infrasound noise levels. TA station locations were not chosen to optimize infrasound performance, and consequently span a dramatic range of land cover types, from temperate rain forest to exposed tundra. In this study, we compute power spectral densities for 2020 data and compile new ambient infrasound low- and high-noise models for the region. In addition, we compare time series of root-mean-squared (rms) amplitudes with wind data and high-resolution land cover data to derive noise–wind speed relationships for several land cover categories. We observe that noise levels for the network are dominated by wind, and that network noise is generally higher in the winter months when storms are more frequent and the microbarom is more pronounced. Wind direction also exerts control on noise levels, likely as a result of infrasound ports being systematically located on the east side of the station huts. We find that rms amplitudes correlate with site land cover type, and that knowledge of both land cover type and wind speed can help predict infrasound noise levels. Our results show that land cover data can be used to inform infrasound station site selection, and that wind–noise models that incorporate station land cover type are useful tools for understanding general station noise performance.

Land Cover

Ambient noise level

10.1785/0220210365

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Aftershock Sequence of the Mw = 7.9 Little Sitkin, Alaska Earthquake of June 23, 2014

K. A. Macpherson N. A. Ruppert

Sequence (biology)

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Revisiting Notable Earthquakes and Seismic Patterns of the Past Decade in Alaska

AGU Fall Meeting Abstracts (2015)

N. A. Ruppert K. A. Macpherson S. G. Holtkamp

Remotely triggered earthquakes

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The 2010 M_w 7.8 Mentawai earthquake: Very shallow source of a rare tsunami earthquake determined from tsunami field survey and near‐field GPS data

Journal of Geophysical Research Atmospheres (2012)

Emma M. Hill J. C. Borrero Zhenhua Huang Qiang Qiu Paramesh Banerjee

The M w 7.8 October 2010 Mentawai, Indonesia, earthquake was a “tsunami earthquake,” a rare type of earthquake that generates a tsunami much larger than expected based on the seismic magnitude. It produced a locally devastating tsunami, with runup commonly in excess of 6 m. We examine this event using a combination of high‐rate GPS data, from instruments located on the nearby islands, and a tsunami field survey. The GPS displacement time series are deficient in high‐frequency energy, and show small coseismic displacements (<22 cm horizontal and <4 cm subsidence). The field survey shows that maximum tsunami runup was >16 m. Our modeling results show that the combination of the small GPS displacements and large tsunami can only be explained by high fault slip at very shallow depths, far from the islands and close to the oceanic trench. Inelastic uplift of trench sediments likely contributed to the size of the tsunami. Recent results for the 2011 M w 9.0 Tohoko‐Oki earthquake have also shown shallow fault slip, but the results from our study, which involves a smaller earthquake, provide much stronger constraints on how shallow the rupture can be, with the majority of slip for the Mentawai earthquake occurring at depths of <6 km. This result challenges the conventional wisdom that the shallow tips of subduction megathrusts are aseismic, and therefore raises important questions both about the mechanical properties of the shallow fault zone and the potential seismic and tsunami hazard of this shallow region.

Tsunami earthquake

Earthquake rupture

Slow earthquake

10.1029/2012jb009159

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Crustal thickness and velocity structure beneath Singapore’s seismic network

Journal of Asian Earth Sciences (2013)

K. A. Macpherson Dannie Hidayat Lujia Feng S. H. Goh

Seismic velocity

10.1016/j.jseaes.2012.12.027

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Citations (13)

Kalman filtering for decade-length modeling of GRACE gravity

AGUFM (2012)

L. Wang J. L. Davis Emma M. Hill K. A. Macpherson

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Receiver function structure beneath a broad-band seismic station in south Sumatra

AGUFM (2010)

K. A. Macpherson D. Hidayat S. H. Goh

Receiver function

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Atmospheric waves and global seismoacoustic observations of the January 2022 Hunga eruption, Tonga

Science (2022)

Robin S. Matoza David Fee Jelle Assink Alexandra M. Iezzi David N. Green

The 15 January 2022 climactic eruption of Hunga volcano, Tonga, produced an explosion in the atmosphere of a size that has not been documented in the modern geophysical record. The event generated a broad range of atmospheric waves observed globally by various ground-based and spaceborne instrumentation networks. Most prominent was the surface-guided Lamb wave (≲0.01 hertz), which we observed propagating for four (plus three antipodal) passages around Earth over 6 days. As measured by the Lamb wave amplitudes, the climactic Hunga explosion was comparable in size to that of the 1883 Krakatau eruption. The Hunga eruption produced remarkable globally detected infrasound (0.01 to 20 hertz), long-range (~10,000 kilometers) audible sound, and ionospheric perturbations. Seismometers worldwide recorded pure seismic and air-to-ground coupled waves. Air-to-sea coupling likely contributed to fast-arriving tsunamis. Here, we highlight exceptional observations of the atmospheric waves.

Seismometer

10.1126/science.abo7063

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The 2010 Mw 7.8 Mentawai earthquake 2012JB009159 supplementaryFigures

Emma M. Hill J. C. Borrero Z. Huang Qiang Qiu Paramesh Banerjee

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Long-period ground motions in the upper Mississippi embayment from finite-fault, finite-difference simulations

K. A. Macpherson

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