Geology topics

Peter Cervelli

Publications and source records attributed to Peter Cervelli.

9 recordsLinked to original sources

USGS2019

Overview, chronology, and impacts of the 2016–2017 eruption of Bogoslof volcano, Alaska

The 2016–2017 eruption of Bogoslof volcano, a back-arc shallow submarine volcano in Alaska’s Aleutian arc, began in December 2016 and included 70 explosive events and at least two episodes of subaerial dome building. Because the volcano had no local monitoring stations during the eruption, a combination of distant seismic stations, regional infrasound sensors, lightning detection, a variety of satellite data and observer reports, and a field visit in 2018, were used to recreate the events that occurred during the nine-month eruption. Following precursory seismicity that started in September 2016, the eruption began in December 2016 with a series of explosive events that persisted through mid-March 2017. After a 6-week hiatus, activity resumed on May 17 and lasted through the end of August 2017 and consisted of additional explosions and two short-lived subaerial lava domes that formed in June and August. For most of the eruption, Bogoslof’s vent was submerged in shallow seawater, though during several of the longer events a subaerial edifice grew, and the vent migrated above sea level resulting in more ash-rich volcanic clouds. Eruptive products, geophysical signals, and eruptive style are all broadly consistent with vulcanian activity where slow magma ascent led to repetitive dome or plug formation, overpressurization in the upper conduit, and sudden release during short-lived explosions. Infiltration of seawater may have prohibited large domes from forming especially in the first half of the eruption when explosions were closely spaced in time. The largest four explosions in the sequence occurred after inter-event times of 10 days or more. Three events produced ashfall on nearby communities and mariners east and south of Bogoslof and the eruption resulted in dozens of flight cancelations and flight diversions around the volcano and its ash clouds.

Alaska↗

USGS2019

The 2018 rift eruption and summit collapse of Kilauea Volcano

In 2018, Kīlauea Volcano experienced its largest lower East Rift Zone (LERZ) eruption and caldera collapse in at least 200 years. After collapse of the Pu'u 'Ō'ō vent on 30 April, magma propagated downrift. Eruptive fissures opened in the LERZ on 3 May, eventually extending ~6.8 km. A 4 May earthquake (M6.9) produced ~5 m of fault slip. Lava erupted at rates exceeding 100 m3/s, eventually covering 35.5 km2. The summit magma system partially drained, producing minor explosions and near-daily collapses releasing energy equivalent to M4.7-M5.4 earthquakes. Activity declined rapidly on 4 August. Summit collapse and lava flow volume estimates are roughly equivalent--about 0.8 km3. Careful historical observation and monitoring of Kīlauea enabled successful forecasting of hazardous events.

Hawaii↗

USGS2009

Tracking magma volume recovery at Okmok Volcano using GPS and an unscented kalman filter

Changes beneath a volcano can be observed through position changes in a GPS network, but distinguishing the source of site motion is not always straightforward. The records of continuous GPS sites provide a favorable data set for tracking magma migration. Dense campaign observations usually provide a better spatial picture of the overall deformation field, at the expense of an episodic temporal record. Combining these observations provides the best of both worlds. A Kalman filter provides a means for integrating discrete and continuous measurements and for interpreting subtle signals. The unscented Kalman filter (UKF) is a nonlinear method for time‐dependent observations. We demonstrate the application of this technique to deformation data by applying it to GPS data collected at Okmok volcano. Seven years of GPS observations at Okmok are analyzed using a Mogi source model and the UKF. The deformation source at Okmok is relatively stable at 2.5 km depth below sea level, located beneath the center of the caldera, which means the surface deformation is caused by changes in the strength of the source. During the 7 years of GPS observations more than 0.5 m of uplift has occurred, a majority of that during the time period January 2003 to July 2004. The total volume recovery at Okmok since the last eruption in 1997 is ∼60–80%. The UKF allows us to solve simultaneously for the time‐dependence of the source strength and for the location without a priori information about the source. 2009 by the American Geophysical Union.

Alaska↗

USGS2006

Corrigendum: Earthquakes triggered by silent slip events on Kīlauea volcano, Hawaii

There was a plotting error in Fig. 1 that inadvertently displays earthquakes for the incorrect time interval. The location of earthquakes during the two-day-long slow-slip event of January 2005 are shown here in the corrected Fig. 1 . Because the incorrect locations were also used in the Coulomb stress-change (CSC) calculation, the error could potentially have biased our interpretation of the depth of the slow-slip event, although in fact it did not. Because nearly all of the earthquakes, both background and triggered, are landward of the slow-slip event and at similar depths (6.5–8.5 km), the impact on the CSC calculations is negligible ( Fig. 2 ; compare with Fig. 4 in original paper). The error does not alter our conclusion that the triggered events during the January 2005 slow-slip event were located on a subhorizontal plane at a depth of 7.5 1 km. This is therefore the most likely depth of the slow-slip events. We thank Cecily J. Wolfe for pointing out the error in the original Fig. 1 .

Hawai'i↗

USGS2006

The National Volcano Early Warning System (NVEWS)

The National Volcano Early Warning System (NVEWS) is a proposed national-scale effort by the U.S. Geological Survey (USGS) Volcano Hazards Program and its affiliated partners in the Consortium of U.S. Volcano Observatories (CUSVO) ( http://www.cusvo.org ) to ensure that volcanoes are monitored at a level commensurate with the threats they pose. Roughly half of the Nation’s 169 young volcanoes are dangerous because of the manner in which they erupt and the communities and infrastructure within their destructive reach. Most U.S. volcanoes are located on sparsely populated Federal lands, but it is the threat to communities and infrastructure downstream and downwind, including to military and commercial aviation, that drives the need to properly monitor volcanic activity and provide forecasts and notifications of expected hazards. Waiting until unrest escalates at a volcano then reacting to improve sparse monitoring arrays results in the loss of precious time and data as scientists, civil authorities, citizens, and businesses play "catch up" with a dangerous force of nature. NVEWS is a proposal to address monitoring needs at potentially dangerous volcanoes that have inadequate ground-based monitoring or none at all and to move beyond a reactive approach to mitigating volcanic risk. The most hazardous volcanoes would be properly monitored well in advance of the onset of activity, making it possible for scientists to improve the timeliness and accuracy of hazard forecasts and for citizens to take proper and timely action to reduce risk. The first step in developing NVEWS was a systematic assessment of (1) threats posed by U.S. volcanoes to human life and enterprise, (2) current monitoring capabilities at each volcano, and (3) improvements necessary to fill the worst monitoring gaps. The NVEWS assessment, published in 2005 ( http://pubs.usgs.gov/of/2005/1164/ ), shows that a few volcanoes are relatively well monitored with telemetered instrument arrays of various types. Many other volcanoes are monitored primarily by a network of sparsely distributed seismic instruments that lack the sensitivity to detect the subtle earthquakes that commonly characterize the earliest stages of unrest. Some hazardous volcanoes have no ground-based monitoring whatsoever. The overall result of the NVEWS assessment is the identification of 57 priority volcanoes that are undermonitored for the threats posed and thus targets for improved monitoring networks.

Fact Sheet↗

USGS2005

Global Positioning System measurements on the island of Hawai`i: 1997 through 2004

This report summarizes GPS data and observations collected between 1997 and 2004 on the island of Hawai‘i with static surveying and continuously recording instruments. On Kīlauea, the long-term deformation field is dominated by steady southeastern velocities of more than 6 cm/year and uplift of about 2 cm/yr at stations on the south flank (with respect to a fixed Pacific Plate). Superimposed on this steady signal are transient displacements associated with magmatic intrusions, earthquakes, and aseismic slip events. The largest of these was the January 30, 1997 dike intrusion and eruption. GPS instruments near Kīlauea’s summit also record numerous additional short-term fluctuations associated with variations in magma reservoir pressure and geometry. From mid-1997 through 2001, the dominant signal at the summit was deflationary, with maximum subsidence of ~5 cm/yr south of Kīlauea caldera. However, inflation of the magma system was observed from late 2001 to May 2002, and from mid-2003 through 2004. The east rift zone eruption continued at the Pu‘u ‘O‘o vent during the entire period of this report. Mauna Loa Volcano, which most recently erupted in 1984, showed low rates of contraction across the summit caldera and southeasterly motion of the southeast flank from 1997 until May 2002. Reinflation started abruptly in May 2002. Inflation contin ued through 2004, but at highly variable rates. Extension rates on a baseline across the summit caldera slowed in October 2002 and increased again starting in mid-2003. The most dramatic change during the inflation period, however, was a significant increase in extension rate on longer baselines, from the northwest to southeast flanks, in July 2004. GPS measurements on Hualalai volcano show no significant motion relative to the Pacific Plate.

Hawai'i↗

USGS2003

The mechanics of unrest at Long Valley caldera, California: 1. Modeling the geometry of the source using GPS, leveling and two-color EDM data

We surveyed 44 existing leveling monuments in Long Valley caldera in July 1999, using dual frequency global positioning system (GPS) receivers. We have been able to tie GPS and leveling to a common reference frame in the Long Valley area and computed the vertical deformation by differencing GPS-based and leveled orthometric heights. The resurgent dome uplifted 74??7 cm from 1975 to 1999. To define the inflation source, we invert two-color EDM and uplift data from the 1985-1999 unrest period using spherical or ellipsoidal sources. We find that the ellipsoidal source satisfies both the vertical and horizontal deformation data, whereas the spherical point source cannot. According to our analysis of the 1985-1999 data, the main source of deformation is a prolate ellipsoid located beneath the resurgent dome at a depth of 5.9 km (95% bounds of 4.9-7.5 km). This body is vertically elongated, has an aspect ratio of 0.475 (95% bounds are 0.25-0.65) and a volume change of 0.086 km3 (95% bounds are 0.06-0.13 km3). Failure to account for the ellipsoidal nature of the source biases the estimated source depth by 2.1 km (35%), and the source volume by 0.038 km3 (44%). ?? 2003 Elsevier B.V. All rights reserved.

Journal of Volcanology and Geothermal Research↗

USGS2002

The 12 September 1999 Upper East Rift Zone dike intrusion at Kilauea Volcano, Hawaii

Deformation associated with an earthquake swarm on 12 September 1999 in the Upper East Rift Zone of Kilauea Volcano was recorded by continuous GPS receivers and by borehole tiltmeters. Analyses of campaign GPS, leveling data, and interferometric synthetic aperture radar (InSAR) data from the ERS-2 satellite also reveal significant deformation from the swarm. We interpret the swarm as resulting from a dike intrusion and model the deformation field using a constant pressure dike source. Nonlinear inversion was used to find the model that best fits the data. The optimal dike is located beneath and slightly to the west of Mauna Ulu, dips steeply toward the south, and strikes nearly east-west. It is approximately 3 by 2 km across and was driven by a pressure of ∼15 MPa. The total volume of the dike was 3.3 × 10 6 m 3 . Tilt data indicate a west to east propagation direction. Lack of premonitory inflation of Kilauea's summit suggests a passive intrusion; that is, the immediate cause of the intrusion was probably tensile failure in the shallow crust of the Upper East Rift Zone brought about by persistent deep rifting and by continued seaward sliding of Kilauea's south flank.

Hawaii↗

USGS2001

Volcano monitoring using the Global Positioning System: Filtering strategies

Permanent Global Positioning System (GPS) networks are routinely used for producing improved orbits and monitoring secular tectonic deformation. For these applications, data are transferred to an analysis center each day and routinely processed in 24-hour segments. To use GPS for monitoring volcanic events, which may last only a few hours, real-time or near real-time data processing and subdaily position estimates are valuable. Strategies have been researched for obtaining station coordinates every 15 min using a Kalman filter; these strategies have been tested on data collected by a GPS network on Kilauea Volcano. Data from this network are tracked continuously, recorded every 30 s, and telemetered hourly to the Hawaiian Volcano Observatory. A white noise model is heavily impacted by data outages and poor satellite geometry, but a properly constrained random walk model fits the data well. Using a borehole tiltmeter at Kilauea's summit as ground-truth, solutions using different random walk constraints were compared. This study indicates that signals on the order of 5 mm/h are resolvable using a random walk standard deviation of 0.45 cm/√h. Values lower than this suppress small signals, and values greater than this have significantly higher noise at periods of 1–6 hours.

Hawai'i↗