Stephen McNutt - Academia.edu (original) (raw)
Papers by Stephen McNutt
Eos, Transactions American Geophysical Union, 2005
Bulletin of the Seismological Society of America, Apr 1, 1990
... THROUGH 30 SEPTEMBER ACTIVITY BY DP HILL, WL ELLSWORTH, MJS JOHNSTON, JO LANGBEIN, DH OPPENHE... more ... THROUGH 30 SEPTEMBER ACTIVITY BY DP HILL, WL ELLSWORTH, MJS JOHNSTON, JO LANGBEIN, DH OPPENHEIMER, AM PITT, PA REASENBERG, ML SOREY, AND SR MCNUTT ABSTRACT Mammoth Mountain is ...
Journal of Volcanology and Geothermal Research, Oct 1, 2000
... generation. A lightning detection system operated in central Alaska by the Bureau of Land Man... more ... generation. A lightning detection system operated in central Alaska by the Bureau of Land Management (BLM) also recorded lightning during the August eruption, but was not operating during the June or September eruptions. ...
2015 AGU Fall Meeting, Dec 18, 2015
The ability to determine volcanic ash plume characteristics from seismic and/or infrasonic record... more The ability to determine volcanic ash plume characteristics from seismic and/or infrasonic records would enable increased accuracy in volcanic monitoring during times of low visibility. During May-June 2015 a field deployment of 6 infrasound sensors, 2 seismometers, multiple cameras, and 10 Lightning Mapping Array (LMA) stations were deployed around Sakurajima Volcano in Japan. During one month of observations (13 May to 10 June) hundreds of explosive eruptions were observed with plume heights reaching 4.3 km above the vent. The plumes varied in duration, ash content, and physical form. The resulting explosions exhibited a variety of infrasound waveforms including the classic long-period N shape as well as events with a mixture of high and low frequencies. For a subset of larger events, peak pressures ranged from 16 to 741 Pa at a distance of 3.6 km from the vent. The seismic signals are long period and emergent with no clear P or S-waves, although high frequency ground-coupled airwaves are visible in conjunction with the infrasonic record of some of the explosive eruptions. Peak ground displacements on the vertical component ranged from 2.1 to 183 um for the same subset of events. Volcanic lightning was both visually observed and recorded on the LMA stations. One of the goals of this project to determine if there are intrinsic relationships between ash plume characteristics, such as initial velocity or acceleration, ash grain size, texture, and composition, seismic and infrasound waveforms, and the presence and type of volcanic lightning. The rich variety of observations provides a good opportunity to determine such relationships
AGU Fall Meeting Abstracts, Dec 1, 2005
ABSTRACT
AGU Fall Meeting Abstracts, Dec 1, 2006
The April 20, 2006 Mw=7.6 earthquake that occurred in Koryakia, Russia, just North of Kamchatka, ... more The April 20, 2006 Mw=7.6 earthquake that occurred in Koryakia, Russia, just North of Kamchatka, produced very clear T-phases on seismic stations in the Aleutian Islands of Alaska. The seismic stations are maintained by the Alaska Volcano Observatory (AVO) to monitor volcanoes. Strong T-phases were recorded by most of the AVO network. The well-distributed locations of the AVO stations along
2016 AGU Fall Meeting, Dec 13, 2016
Volcanic plumes resulting from explosive eruptions are commonly electrified and lightning is freq... more Volcanic plumes resulting from explosive eruptions are commonly electrified and lightning is frequently observed during eruptions. Over the past 10 years VHF lightning mapping arrays (LMAs) have been used to study the electrical discharges in volcanic plumes from volcanoes in Alaska (USA), Iceland, Chile, and Japan. In addition to VHF emissions typical of lightning, during explosive eruptions LMAs have also recorded a source of VHF radiation distinct from lightning. This distinct source of radiation is referred to as continuous RF (CRF) and is characterized by relatively high rates of impulsive radiation events over long time scales (several to tens of seconds). Continuous RF is observed simultaneous with the onset of explosive eruptions and originates at low altitude -- at or near the vent of the volcano. Continuous RF has only been observed while the volcano is actively ejecting ash. The source of the CRF is unknown, but has been hypothesized to be due to numerous, small (~100 m), leader-forming discharges at the vent of the volcano. A new study is underway to gain further insight into the source of CRF emissions. In May and June of 2015 multi-parametric observations of volcanic lightning were conducted at Sakurajima volcano in Japan. Sakurajima produces frequent small-scale eruptions (plume heights 1-3 km) and during the main observation period several hundred explosive events occurred. The electrical activity was measured with a 10 station LMA, log-RF waveform, a broadband VHF antenna, slow and fast antennas, high-speed video, and still photography. Seismometers, infrasound sensors, infrared video, and low light video were used to measure the eruptive activity. We present an overview of the CRF observations obtained during the field deployment in Japan, including the electrical characteristics of CRF and the characteristics of the eruptive activity producing the CRF
2015 AGU Fall Meeting, Dec 16, 2015
In May 2015 our volcano-lightning team spent about 2 weeks at the Sakurajima volcano observing el... more In May 2015 our volcano-lightning team spent about 2 weeks at the Sakurajima volcano observing electrical activity during many explosive eruptions. The explosive eruptions sent ash into the atmosphere reaching between 2 and 5 km MSL. Most of the eruptions produced lightning and electrical activity. Our measurements included electric, photographic, seismic, and ascustic. The atmospheric-electricity instruments included a 10-station-LMA, slow antenna, fast antenna, and broad-band-RF. Inaddition to standard photography and video, we had infrared video, low-light video, and high-speed video. The slow antenna showed that typically the predominant charge was negative, but at times it was positive. The larger eruptions show the continual electrical discharges that begin coincident within tenths of a second as the explosion. We have sensed these small discharges in many other volcanic eruptions
AGU Fall Meeting Abstracts, Dec 1, 2004
ABSTRACT
U.S. Geological Survey professional paper, 2010
U.S. Geological Survey professional paper, 2010
We use seismic b-values to explore physical processes during the Augustine Volcano 2005-6 preerup... more We use seismic b-values to explore physical processes during the Augustine Volcano 2005-6 preeruptive earthquake swarm. The preeruptive earthquake swarm was divided into two parts: the "long swarm," which extended from April 30, 2005, to January 10, 2006; and the "short swarm," which started 13 hours before the onset of explosive activity on January 11, 2006. Calculations of b-value for each of these swarms and for a background period were performed. The short swarm, directly preceding the eruption, had the lowest calculated b-value. In addition to the low value, the shape of the b-value plot for the short swarm appears to have two separate slopes, a shallower slope for magnitudes as great as 1.2 and a steeper slope for magnitudes greater than 1.2. Calculations of b were also run for three precursory deformation stages suggested by a separate investigation of deformation at Augustine Volcano. The highest b-value, found in stage 2, may indicate an increase in pore pressure and in thermal gradient, which matches the geodetic interpretation of a proposed dike intrusion. Finer resolution changes of b are explored through calculations of b-value versus time. An initial drop in b-value in late 2004 preceded the onset of increased seismicity. The temporal nature of this change and its timing are corroborated by atmospheric temperature data recorded on the summit of the volcano, which increased at approximately the same time. Stress at Augustine Volcano was also studied using 79 earthquakes that returned acceptable focal mechanisms
Annual Review of Earth and Planetary Sciences, May 31, 2005
Recent developments in volcanic seismology include new techniques to improve earthquake locations... more Recent developments in volcanic seismology include new techniques to improve earthquake locations that have changed clouds of earthquakes to lines (faults) for high-frequency events and small volumes for low-frequency (LF) events. Spatial mapping of the b-value shows regions of normal b and high b anomalies at depths of 3-4 and 7-10 km. Increases in b precede some eruptions. LF events and very-long-period (VLP) events have been recorded at many volcanoes, and models are becoming increasingly sophisticated. Deep long-period (LP) events are fairly common, but may represent several processes. Acoustic sensors have greatly improved the study of volcanic explosions. Volcanic tremor is stronger for fissure eruptions, phreatic eruptions, and higher gas contents. Path and site effects can be extreme at volcanoes. Seismicity at volcanoes is triggered by large earthquakes, although mechanisms are still uncertain. A number of volcanoes have significant deformation with very little seismicity. Tomography has benefited from improved techniques and better instrumental arrays.
Eos, Transactions American Geophysical Union, May 15, 2012
Journal of Volcanology and Geothermal Research, 1994
Seismological Research Letters, 2004
Eos, Transactions American Geophysical Union, 2005
Bulletin of the Seismological Society of America, Apr 1, 1990
... THROUGH 30 SEPTEMBER ACTIVITY BY DP HILL, WL ELLSWORTH, MJS JOHNSTON, JO LANGBEIN, DH OPPENHE... more ... THROUGH 30 SEPTEMBER ACTIVITY BY DP HILL, WL ELLSWORTH, MJS JOHNSTON, JO LANGBEIN, DH OPPENHEIMER, AM PITT, PA REASENBERG, ML SOREY, AND SR MCNUTT ABSTRACT Mammoth Mountain is ...
Journal of Volcanology and Geothermal Research, Oct 1, 2000
... generation. A lightning detection system operated in central Alaska by the Bureau of Land Man... more ... generation. A lightning detection system operated in central Alaska by the Bureau of Land Management (BLM) also recorded lightning during the August eruption, but was not operating during the June or September eruptions. ...
2015 AGU Fall Meeting, Dec 18, 2015
The ability to determine volcanic ash plume characteristics from seismic and/or infrasonic record... more The ability to determine volcanic ash plume characteristics from seismic and/or infrasonic records would enable increased accuracy in volcanic monitoring during times of low visibility. During May-June 2015 a field deployment of 6 infrasound sensors, 2 seismometers, multiple cameras, and 10 Lightning Mapping Array (LMA) stations were deployed around Sakurajima Volcano in Japan. During one month of observations (13 May to 10 June) hundreds of explosive eruptions were observed with plume heights reaching 4.3 km above the vent. The plumes varied in duration, ash content, and physical form. The resulting explosions exhibited a variety of infrasound waveforms including the classic long-period N shape as well as events with a mixture of high and low frequencies. For a subset of larger events, peak pressures ranged from 16 to 741 Pa at a distance of 3.6 km from the vent. The seismic signals are long period and emergent with no clear P or S-waves, although high frequency ground-coupled airwaves are visible in conjunction with the infrasonic record of some of the explosive eruptions. Peak ground displacements on the vertical component ranged from 2.1 to 183 um for the same subset of events. Volcanic lightning was both visually observed and recorded on the LMA stations. One of the goals of this project to determine if there are intrinsic relationships between ash plume characteristics, such as initial velocity or acceleration, ash grain size, texture, and composition, seismic and infrasound waveforms, and the presence and type of volcanic lightning. The rich variety of observations provides a good opportunity to determine such relationships
AGU Fall Meeting Abstracts, Dec 1, 2005
ABSTRACT
AGU Fall Meeting Abstracts, Dec 1, 2006
The April 20, 2006 Mw=7.6 earthquake that occurred in Koryakia, Russia, just North of Kamchatka, ... more The April 20, 2006 Mw=7.6 earthquake that occurred in Koryakia, Russia, just North of Kamchatka, produced very clear T-phases on seismic stations in the Aleutian Islands of Alaska. The seismic stations are maintained by the Alaska Volcano Observatory (AVO) to monitor volcanoes. Strong T-phases were recorded by most of the AVO network. The well-distributed locations of the AVO stations along
2016 AGU Fall Meeting, Dec 13, 2016
Volcanic plumes resulting from explosive eruptions are commonly electrified and lightning is freq... more Volcanic plumes resulting from explosive eruptions are commonly electrified and lightning is frequently observed during eruptions. Over the past 10 years VHF lightning mapping arrays (LMAs) have been used to study the electrical discharges in volcanic plumes from volcanoes in Alaska (USA), Iceland, Chile, and Japan. In addition to VHF emissions typical of lightning, during explosive eruptions LMAs have also recorded a source of VHF radiation distinct from lightning. This distinct source of radiation is referred to as continuous RF (CRF) and is characterized by relatively high rates of impulsive radiation events over long time scales (several to tens of seconds). Continuous RF is observed simultaneous with the onset of explosive eruptions and originates at low altitude -- at or near the vent of the volcano. Continuous RF has only been observed while the volcano is actively ejecting ash. The source of the CRF is unknown, but has been hypothesized to be due to numerous, small (~100 m), leader-forming discharges at the vent of the volcano. A new study is underway to gain further insight into the source of CRF emissions. In May and June of 2015 multi-parametric observations of volcanic lightning were conducted at Sakurajima volcano in Japan. Sakurajima produces frequent small-scale eruptions (plume heights 1-3 km) and during the main observation period several hundred explosive events occurred. The electrical activity was measured with a 10 station LMA, log-RF waveform, a broadband VHF antenna, slow and fast antennas, high-speed video, and still photography. Seismometers, infrasound sensors, infrared video, and low light video were used to measure the eruptive activity. We present an overview of the CRF observations obtained during the field deployment in Japan, including the electrical characteristics of CRF and the characteristics of the eruptive activity producing the CRF
2015 AGU Fall Meeting, Dec 16, 2015
In May 2015 our volcano-lightning team spent about 2 weeks at the Sakurajima volcano observing el... more In May 2015 our volcano-lightning team spent about 2 weeks at the Sakurajima volcano observing electrical activity during many explosive eruptions. The explosive eruptions sent ash into the atmosphere reaching between 2 and 5 km MSL. Most of the eruptions produced lightning and electrical activity. Our measurements included electric, photographic, seismic, and ascustic. The atmospheric-electricity instruments included a 10-station-LMA, slow antenna, fast antenna, and broad-band-RF. Inaddition to standard photography and video, we had infrared video, low-light video, and high-speed video. The slow antenna showed that typically the predominant charge was negative, but at times it was positive. The larger eruptions show the continual electrical discharges that begin coincident within tenths of a second as the explosion. We have sensed these small discharges in many other volcanic eruptions
AGU Fall Meeting Abstracts, Dec 1, 2004
ABSTRACT
U.S. Geological Survey professional paper, 2010
U.S. Geological Survey professional paper, 2010
We use seismic b-values to explore physical processes during the Augustine Volcano 2005-6 preerup... more We use seismic b-values to explore physical processes during the Augustine Volcano 2005-6 preeruptive earthquake swarm. The preeruptive earthquake swarm was divided into two parts: the "long swarm," which extended from April 30, 2005, to January 10, 2006; and the "short swarm," which started 13 hours before the onset of explosive activity on January 11, 2006. Calculations of b-value for each of these swarms and for a background period were performed. The short swarm, directly preceding the eruption, had the lowest calculated b-value. In addition to the low value, the shape of the b-value plot for the short swarm appears to have two separate slopes, a shallower slope for magnitudes as great as 1.2 and a steeper slope for magnitudes greater than 1.2. Calculations of b were also run for three precursory deformation stages suggested by a separate investigation of deformation at Augustine Volcano. The highest b-value, found in stage 2, may indicate an increase in pore pressure and in thermal gradient, which matches the geodetic interpretation of a proposed dike intrusion. Finer resolution changes of b are explored through calculations of b-value versus time. An initial drop in b-value in late 2004 preceded the onset of increased seismicity. The temporal nature of this change and its timing are corroborated by atmospheric temperature data recorded on the summit of the volcano, which increased at approximately the same time. Stress at Augustine Volcano was also studied using 79 earthquakes that returned acceptable focal mechanisms
Annual Review of Earth and Planetary Sciences, May 31, 2005
Recent developments in volcanic seismology include new techniques to improve earthquake locations... more Recent developments in volcanic seismology include new techniques to improve earthquake locations that have changed clouds of earthquakes to lines (faults) for high-frequency events and small volumes for low-frequency (LF) events. Spatial mapping of the b-value shows regions of normal b and high b anomalies at depths of 3-4 and 7-10 km. Increases in b precede some eruptions. LF events and very-long-period (VLP) events have been recorded at many volcanoes, and models are becoming increasingly sophisticated. Deep long-period (LP) events are fairly common, but may represent several processes. Acoustic sensors have greatly improved the study of volcanic explosions. Volcanic tremor is stronger for fissure eruptions, phreatic eruptions, and higher gas contents. Path and site effects can be extreme at volcanoes. Seismicity at volcanoes is triggered by large earthquakes, although mechanisms are still uncertain. A number of volcanoes have significant deformation with very little seismicity. Tomography has benefited from improved techniques and better instrumental arrays.
Eos, Transactions American Geophysical Union, May 15, 2012
Journal of Volcanology and Geothermal Research, 1994
Seismological Research Letters, 2004