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Charles W. Wicks

Publications and source records attributed to Charles W. Wicks.

At least 19 recordsLinked to original sources
USGS2019

Coseismic slip and early afterslip of the M6.0 August 24, 2014 South Napa, California, earthquake

We employ strong motion seismograms and static offsets from the Global Positioning System, Interferometric Synthetic Aperture Radar, and other measurements in order to derive a coseismic slip and afterslip model of the M6.0 24 August 2014 South Napa earthquake. This earthquake ruptured an ∼13‐km‐long portion of the West Napa fault with predominantly right‐lateral strike slip. In the kinematic seismic slip inversions, we couple the coseismic slip and afterslip distributions by requiring both distributions to involve right‐lateral strike slip with positive amplitude, with the net static slip being the sum of the two. We consider several candidate fault geometries: a first involving two steeply east dipping fault planes that reach Earth's surface at the western surface trace (STW), where most surface rupture was observed, a second involving a steeply west dipping plane that also reaches Earth's surface at the STW, and a third involving a combination of two variably west dipping planes constrained to pass through the locus of postseismic seismicity located ∼1 km west of the STW. The data are best fit using the model of two east dipping fault planes, with coseismic slip up to ∼1.2 m on a dominant shallow asperity about 10 km north of the hypocenter and on deeper asperities on the southern part of the rupture. Afterslip up to 1 m is concentrated along the southern part of the rupture at depths 5 km, consistent with surface observations of afterslip. Seismic moments associated with coseismic slip and afterslip are 1.13×10 18 N m (Mw 6.00) and 3.64×10 17 N m, respectively.

California↗
USGS2019

Space-based imaging radar studies of U.S. volcanoes

The arrival of space-based imaging radar as a revolutionary land-surface mapping and monitoring tool little more than a quarter century ago enabled a spate of innovative volcano research worldwide. Soon after launch of European Space Agency’s ERS-1 spacecraft in 1991, the U.S. Geological Survey began SAR and InSAR studies of volcanoes in the Aleutian and Cascades arcs, in Hawai’i, and elsewhere in the western U.S. including the Yellowstone and Long Valley calderas. This paper summarizes results of that effort and presents new findings concerning: (1) prevalence of volcano deformation in the Aleutian and Cascade arcs; (2) surface-change detection and hazard assessment during eruptions at Aleutian and Hawaiian volcanoes; (3) geodetic imaging of magma storage and transport systems in Hawai’i; and (4) deformation sources and processes at the Yellowstone and Long Valley calderas. Surface deformation caused by a variety of processes is common in arc settings and could easily escape detection without systematic InSAR surveillance. Space-based SAR imaging of active lava flows and domes in remote or heavily vegetated settings, including during periods of bad weather and darkness, extends land-based monitoring capabilities and improves hazards assessments. At Kīlauea Volcano, comprehensive SAR and InSAR observations identify multiple magma storage zones beneath the summit area and along the East Rift Zone, and illuminate magma transport pathways. The same approach at Yellowstone tracks the ascent of magmatic volatiles from a mid-crustal intrusion to shallow depth and relates that process to increased hydrothermal activity at the surface. Together with recent and planned launches of highly capable imaging-radar satellites, these findings support an optimistic outlook for near-real time surveillance of volcanoes at global scale in the coming decade.

Frontiers in Earth Science↗
USGS2017

Geodetic slip model of the 3 September 2016 Mw 5.8 Pawnee, Oklahoma, earthquake: Evidence for fault‐zone collapse

The 3 September 2016 M w 5.8 Pawnee earthquake in northern Oklahoma is the largest earthquake ever recorded in Oklahoma. The coseismic deformation was measured with both Interferometric Synthetic Aperture Radar and Global Positioning System (GPS), with measureable signals of order 1 cm and 1 mm, respectively. We derive a coseismic slip model from Sentinel‐1A and Radarsat 2 interferograms and GPS static offsets, dominated by distributed left‐lateral strike slip on a primary west‐northwest–east‐southeast‐trending subvertical plane, whereas strike slip is concentrated near the hypocenter (5.6 km depth), with maximum slip of ∼1 m located slightly east and down‐dip of the hypocenter. Based on systematic misfits of observed interferogram line‐of‐sight (LoS) displacements, with LoS based on shear‐dislocation models, a few decimeters of fault‐zone collapse are inferred in the hypocentral region where coseismic slip was the largest. This may represent the postseismic migration of large volumes of fluid away from the high‐slip areas, made possible by the creation of a temporary high‐permeability damage zone around the fault.

Oklahoma↗
USGS2017

Semipermanent GPS (SPGPS) as a volcano monitoring tool: Rationale, method, and applications

Semipermanent GPS (SPGPS) is an alternative to conventional campaign or survey-mode GPS (SGPS) and to continuous GPS (CGPS) that offers several advantages for monitoring ground deformation. Unlike CGPS installations, SPGPS stations can be deployed quickly in response to changing volcanic conditions or earthquake activity such as a swarm or aftershock sequence. SPGPS networks can be more focused or more extensive than CGPS installations, because SPGPS equipment can be moved from station to station quickly to increase the total number of stations observed in a given time period. SPGPS networks are less intrusive on the landscape than CGPS installations, which makes it easier to satisfy land-use restrictions in ecologically sensitive areas. SPGPS observations are preferred over SGPS measurements because they provide better precision with only a modest increase in the amount of time, equipment, and personnel required in the field. We describe three applications of the SPGPS method that demonstrate its utility and flexibility. At the Yellowstone caldera, Wyoming, a 9-station SPGPS network serves to densify larger preexisting networks of CGPS and SGPS stations. At the Three Sisters volcanic center, Oregon, a 14-station SPGPS network complements an SGPS network and extends the geographic coverage provided by 3 CGPS stations permitted under wilderness land-use restrictions. In the Basin and Range province in northwest Nevada, a 6-station SPGPS network has been established in response to a prolonged earthquake swarm in an area with only sparse preexisting geodetic coverage. At Three Sisters, the estimated precision of station velocities based on annual ~ 3 month summertime SPGPS occupations from 2009 to 2015 is approximately half that for nearby CGPS stations. Conversely, SPGPS-derived station velocities are about twice as precise as those based on annual ~ 1 week SGPS measurements. After 5 years of SPGPS observations at Three Sisters, the precision of velocity determinations is estimated to be 0.5 mm/yr in longitude, 0.6 mm/yr in latitude, and 0.8 mm/yr in height. We conclude that an optimal approach to monitoring volcano deformation includes complementary CGPS and SPGPS networks, periodic InSAR observations, and measurements from in situ borehole sensors such as tiltmeters or strainmeters. This comprehensive approach provides the spatial and temporal detail necessary to adequately characterize a complex and evolving deformation pattern. Such information is essential to multi-parameter models of magmatic or tectonic processes that can help to guide research efforts, and also to inform hazards assessments and land-use planning decisions.

Journal of Volcanology and Geothermal Research↗
USGS2015

Renewed inflation of Long Valley Caldera, California (2011 to 2014)

Slow inflation began at Long Valley Caldera in late 2011, coinciding with renewed swarm seismicity. Ongoing deformation is concentrated within the caldera. We analyze this deformation using a combination of GPS and InSAR (TerraSAR-X) data processed with a persistent scatterer technique. The extension rate of the dome-crossing baseline during this episode (CA99 to KRAC) is 1 cm/yr, similar to past inflation episodes (1990–1995 and 2002–2003), and about a tenth of the peak rate observed during the 1997 unrest. The current deformation is well modeled by the inflation of a prolate spheroidal magma reservoir ∼7 km beneath the resurgent dome, with a volume change of ∼6 × 10 6  m 3 /yr from 2011.7 through the end of 2014. The current data cannot resolve a second source, which was required to model the 1997 episode. This source appears to be in the same region as previous inflation episodes, suggesting a persistent reservoir.

California↗
USGS2014

Key recovery factors for the August 24, 2014, South Napa Earthquake

Through discussions between the Federal Emergency Management Agency (FEMA) and the U.S. Geological Survey (USGS) following the South Napa earthquake, it was determined that several key decision points would be faced by FEMA for which additional information should be sought and provided by USGS and its partners. This report addresses the four tasks that were agreed to. These tasks are (1) assessment of ongoing fault movement (called afterslip) especially in the Browns Valley residential neighborhood, (2) assessment of the shaking pattern in the downtown area of the City of Napa, (3) improvement of information on the fault hazards posed by the West Napa Fault System (record of past earthquakes and slip rate, for example), and (4) imagery acquisition and data processing to provide overall geospatial information support to FEMA.

California↗
USGS2013

InSAR Evidence for an active shallow thrust fault beneath the city of Spokane Washington, USA

In 2001, a nearly five month long sequence of shallow, mostly small magnitude earthquakes occurred beneath the city of Spokane, a city with a population of about 200,000, in the state of Washington. During most of the sequence, the earthquakes were not well located because seismic instrumentation was sparse. Despite poor-quality locations, the earthquake hypocenters were likely very shallow, because residents near the city center both heard and felt many of the earthquakes. The combination of poor earthquake locations and a lack of known surface faults with recent movement make assessing the seismic hazards related to the earthquake swarm difficult. However, the potential for destruction from a shallow moderate-sized earthquake is high, for example Christchurch New Zealand in 2011, so assessing the hazard potential of a seismic structure involved in the Spokane earthquake sequence is important. Using interferometric synthetic aperture radar (InSAR) data from the European Space Agency ERS2 and ENVISAT satellites and the Canadian Space Agency RADARSAT-1, satellite we are able to show that slip on a shallow previously unknown thrust fault, which we name the Spokane Fault, is the source of the earthquake sequence. The part of the Spokane Fault that slipped during the 2001 earthquake sequence underlies the north part of the city, and slip on the fault was concentrated between ~0.3 and 2 km depth. Projecting the buried fault plane to the surface gives a possible surface trace for the Spokane Fault that strikes northeast from the city center into north Spokane.

Washington↗
USGS2012

History of surface displacements at the Yellowstone Caldera, Wyoming, from leveling surveys and InSAR observations, 1923-2008

Modern geodetic studies of the Yellowstone caldera, Wyoming, and its extraordinary tectonic, magmatic, and hydrothermal systems date from an initial leveling survey done throughout Yellowstone National Park in 1923 by the U.S. Coast and Geodetic Survey. A repeat park-wide survey by the U.S. Geological Survey (USGS) and the University of Utah during 1975-77 revealed that the central part of the caldera floor had risen more than 700 mm since 1923, at an average rate of 14±1 mm/yr. From 1983 to 2007, the USGS conducted 15 smaller surveys of a single level line that crosses the northeast part of the caldera, including the area where the greatest uplift had occurred from 1923 to 1975-77. The 1983 and 1984 surveys showed that uplift had continued at an average rate of 22±1 mm/yr since 1975-77, but no additional uplift occurred during 1984-85 (-2±5 mm/yr), and during 1985-95 the area subsided at an average rate of 19±1 mm/yr. The change from uplift to subsidence was accompanied by an earthquake swarm, the largest ever recorded in the Yellowstone area (as of March 2012), starting in October 1985 and located near the northwest rim of the caldera. Interferometric synthetic aperture radar (InSAR) images showed that the area of greatest subsidence migrated from the northeast part of the caldera (including the Sour Creek resurgent dome) during 1992-93 to the southwest part (including the Mallard Lake resurgent dome) during 1993-95. Thereafter, uplift resumed in the northeast part of the caldera during 1995-96, while subsidence continued in the southwest part. The onset of uplift migrated southwestward, and by mid-1997, uplift was occurring throughout the entire caldera (essentially rim to rim, including both domes). Consistent with these InSAR observations, leveling surveys indicated 24±3 mm of uplift in the northeast part of the caldera during 1995-98. The beginning of uplift was coincident with or followed shortly after an earthquake swarm near the north caldera rim during June-July 1995 - the strongest swarm since 1985. Rather than a single deformation source as inferred from leveling surveys, the InSAR images revealed two distinct sources - one beneath each resurgent dome on the caldera floor. Subsequently, repeated GPS surveys (sometimes referred to as "campaign" surveys to distinguish them from continuous GPS observations) and InSAR images revealed a third deformation source beneath the north caldera rim. The north-rim source started to inflate in or about 1995, resulting in as much as 80 mm of surface uplift by 2000. Meanwhile, motion of the caldera floor changed from uplift to subsidence during 1997-8. The north rim area rose, while the entire caldera floor (including both domes) subsided until 2002, when both motions paused. Uplift in the northeast part of the caldera resumed in mid-2004 at a historically unprecedented rate of as much as 70 mm/yr, while the north rim area subsided at a lesser rate. Resurveys of the level line across the northeast part of the caldera in 2005 and 2007 indicated the greatest average uplift rate since the initial survey in 1923-53±3 mm/yr. Data from a nearby continuous GPS (CGPS) station showed that the uplift rate slowed to 40-50 mm/yr during 2007-8 and to near zero by September 2009. Following an intense earthquake swarm during January-February 2010, this one near the northwest caldera rim and the strongest since the 1985 swarm in the same general area, CGPS stations recorded the onset of subsidence throughout the entire caldera. Any viable model for the cause(s) of ground deformation at Yellowstone should account for (1) three distinct deformation sources and their association with both resurgent domes and the north caldera rim; (2) interplay among these sources, as suggested by the timing of major changes in deformation mode; (3) migration of the area of greatest subsidence or uplift from the northeast part of the caldera to the southwest part during 1992-95 and 1995-97, respectively; (4) repeated cycles of uplift and subsidence and sudden changes from uplift to subsidence or vice versa; (5) spatial and temporal relationships between changes in deformation mode and strong earthquake swarms; and (6) lateral dimensions of all three deforming areas that indicate source depths in the range of 5 to 15 km. We prefer a conceptual model in which surface displacements at Yellowstone are caused primarily by variations in the flux of basaltic magma into the crust beneath the caldera. Specifically, we envision a magmatic conduit system beneath the northeast part of the caldera that supplies basalt from a mantle source to an accumulation zone at 5-10 km depth, perhaps at a rheological boundary within a crystallizing rhyolite body remnant from past eruptions. Increases in the magma flux favor uplift of the caldera and decreases favor subsidence. A delicate equilibrium exists among the mass and heat flux from basaltic intrusions, heat and volatile loss from the crystallizing rhyolite body, and the overlying hydrothermal system. In the absence of basalt input, steady subsidence occurs mainly as a result of fluid loss from crystallizing rhyolite. At times when a self-sealing zone in the deep hydrothermal system prevents the escape of magmatic fluid, the resulting pressure increase contributes to surface uplift within the caldera; such episodes end when the seal ruptures during an earthquake swarm. To account for the north rim deformation source, we propose that magma or fluid exsolved from magma episodically escapes the caldera system at the three-way structural intersection of (1) the northern caldera boundary, (2) an active seismic belt to the north-northwest that is associated with the Hebgen Lake fault zone, and (3) the Norris - Mammoth corridor - a zone of faults, volcanic vents, and thermal activity that strikes north from the north rim of the caldera near Norris Geyser Basin to Mammoth Hot Springs near the northern boundary of Yellowstone National Park. Increased fluid flux out of the caldera by way of this intersection favors subsidence of the north rim area, and decreased flux favors uplift. This model does not account for poroelastic and thermoelastic effects, nonelastic rheology, or heat and mass transport in the hot and wet subcaldera crust. Such effects almost surely play a role in caldera deformation and are an important topic of ongoing research.

Wyoming↗
USGS2011

The role of dyking and fault control in the rapid onset of eruption at Chaitén Volcano, Chile

Rhyolite is the most viscous of liquid magmas, so it was surprising that on 2 May 2008 at Chaitén Volcano, located in Chile’s southern Andean volcanic zone, rhyolitic magma migrated from more than 5 km depth in less than 4 hours and erupted explosively with only two days of detected precursory seismic activity . The last major rhyolite eruption before that at Chaitén was the largest volcanic eruption in the twentieth century, at Novarupta volcano, Alaska, in 1912. Because of the historically rare and explosive nature of rhyolite eruptions and because of the surprisingly short warning before the eruption of the Chaitén volcano, any information about the workings of the magmatic system at Chaitén, and rhyolitic systems in general, is important from both the scientific and hazard perspectives. Here we present surface deformation data related to the Chaitén eruption based on radar interferometry observations from the Japan Aerospace Exploration Agency (JAXA) DAICHI (ALOS) satellite. The data on this explosive rhyolite eruption indicate that the rapid ascent of rhyolite occurred through dyking and that melt segregation and magma storage were controlled by existing faults.

Chaitén Volcano↗
USGS2011

Deformation of the 2002 Denali Fault earthquakes, mapped by Radarsat-1 interferometry

The magnitude 7.9 earthquake that struck central Alaska on 3 November 2002 was the largest strike-slip earthquake in North America for more than 150 years. The earthquake ruptured about 340 km of the Denali Fault system with observed right-lateral offsets of up to 9 m [ Eberhart-Phillips et al. , 2003] (Figure l). The rupture initiated with slip on a previously unknown thrust fault, the 40-km-long Susitna Glacier Fault. The rupture propagated eastward for about 220 km along the right-lateral Denali Fault where right-lateral slip averaged ˜5 m, before stepping southeastward onto the Totschunda Fault for about 70 km, with offsets as large as 2 m. The 3 November earthquake was preceded by a magnitude 6.7 shock on 23 October—the Nenana Mountain Earthquake—which was located about 25 km to the west of the 3 November earthquake.

Eos, Transactions, American Geophysical Union↗
USGS2011

Enhancement of long period components of recorded and synthetic ground motions using InSAR

Tall buildings and flexible structures require a better characterization of long period ground motion spectra than the one provided by current seismic building codes. Motivated by that, a methodology is proposed and tested to improve recorded and synthetic ground motions which are consistent with the observed co-seismic displacement field obtained from interferometric synthetic aperture radar (InSAR) analysis of image data for the Tocopilla 2007 earthquake ( M w =7.7) in Northern Chile. A methodology is proposed to correct the observed motions such that, after double integration, they are coherent with the local value of the residual displacement. Synthetic records are generated by using a stochastic finite-fault model coupled with a long period pulse to capture the long period fling effect. It is observed that the proposed co-seismic correction yields records with more accurate long-period spectral components as compared with regular correction schemes such as acausal filtering. These signals provide an estimate for the velocity and displacement spectra, which are essential for tall-building design. Furthermore, hints are provided as to the shape of long-period spectra for seismic zones prone to large co-seismic displacements such as the Nazca-South American zone.

Tocopilla↗
USGS2009

Continuing inflation at Three Sisters volcanic center, central Oregon Cascade Range, USA, from GPS, leveling, and InSAR observations

Uplift of a broad area centered ~6 km west of the summit of South Sister volcano started in September 1997 (onset estimated from model discussed in this paper) and was continuing when surveyed in August 2006. Surface displacements were measured whenever possible since August 1992 with satellite radar interferometry (InSAR), annually since August 2001 with GPS and leveling surveys, and with continuous GPS since May 2001. The average maximum displacement rate from InSAR decreased from 3–5 cm/yr during 1998–2001 to ~1.4 cm/yr during 2004–2006. The other datasets show a similar pattern, i.e., surface uplift and extension rates decreased over time but deformation continued through August 2006. Our best-fit model to the deformation data is a vertical, prolate, spheroidal point-pressure source located 4.9–5.4 km below the surface. The source inflation rate decreased exponentially during 2001–2006 with a 1/ e decay time of 5.3 ± 1.1 years. The net increase in source volume from September 1997 to August 2006 was 36.5–41.9 x 10 6 m 3 . A swarm of ~300 small ( M max = 1.9) earthquakes occurred beneath the deforming area in March 2004; no other unusual seismicity has been noted. Similar deformation episodes in the past probably would have gone unnoticed if, as we suspect, most are small intrusions that do not culminate in eruptions.

Oregon↗
USGS2006

Geodetic observations and modeling of magmatic inflation at the Three Sisters volcanic center, central Oregon Cascade Range, USA

Tumescence at the Three Sisters volcanic center began sometime between summer 1996 and summer 1998 and was discovered in April 2001 using interferometric synthetic aperture radar (InSAR). Swelling is centered about 5 km west of the summit of South Sister, a composite basaltic-andesite to rhyolite volcano that last erupted between 2200 and 2000 yr ago, and it affects an area ∼20 km in diameter within the Three Sisters Wilderness. Yearly InSAR observations show that the average maximum displacement rate was 3–5 cm/yr through summer 2001, and the velocity of a continuous GPS station within the deforming area was essentially constant from June 2001 to June 2004. The background level of seismic activity has been low, suggesting that temperatures in the source region are high enough or the strain rate has been low enough to favor plastic deformation over brittle failure. A swarm of about 300 small earthquakes ( M max = 1.9) in the northeast quadrant of the deforming area on March 23–26, 2004, was the first notable seismicity in the area for at least two decades. The U.S. Geological Survey (USGS) established tilt-leveling and EDM networks at South Sister in 1985–1986, resurveyed them in 2001, the latter with GPS, and extended them to cover more of the deforming area. The 2001 tilt-leveling results are consistent with the inference drawn from InSAR that the current deformation episode did not start before 1996, i.e., the amount of deformation during 1995–2001 from InSAR fully accounts for the net tilt at South Sister during 1985–2001 from tilt-leveling. Subsequent InSAR, GPS, and leveling observations constrain the source location, geometry, and inflation rate as a function of time. A best-fit source model derived from simultaneous inversion of all three datasets is a dipping sill located 6.5 ± 2.5 km below the surface with a volume increase of 5.0 × 10 6 ± 1.5 × 10 6 m 3 /yr (95% confidence limits). The most likely cause of tumescence is a pulse of basaltic magma intruding the upper crust along the brittle–ductile interface — a process that must occur episodically beneath the Cascade Range but in the past would have escaped detection in the absence of unusual seismicity. We speculate that such intrusive episodes last from days to years and are separated by quiescent periods of decades to centuries. The likelihood that the current episode at Three Sisters will culminate in an eruption is judged to be low, but the impact of an eruption could be great. The USGS has updated its volcano hazards assessment for the Three Sisters region, notified appropriate agencies and the public, and is helping to prepare an emergency coordination and communication plan.

Central Oregon Cascade Range, Three Sisters volcan↗
USGS2006

Uplift, thermal unrest and magma intrusion at Yellowstone caldera

The Yellowstone caldera, in the western United States, formed 640,000 years ago when an explosive eruption ejected 1,000 km 3 of material 1 . It is the youngest of a series of large calderas that formed during sequential cataclysmic eruptions that began 16 million years ago in eastern Oregon and northern Nevada. The Yellowstone caldera was largely buried by rhyolite lava flows during eruptions that occurred from 150,000 to 70,000 years ago 1 . Since the last eruption, Yellowstone has remained restless, with high seismicity, continuing uplift/subsidence episodes with movements of 70 cm historically 2 to several metres since the Pleistocene epoch 3 , and intense hydrothermal activity. Here we present observations of a new mode of surface deformation in Yellowstone, based on radar interferometry observations from the European Space Agency ERS-2 satellite. We infer that the observed pattern of uplift and subsidence results from variations in the movement of molten basalt into and out of the Yellowstone volcanic system.

Wyoming↗
USGS2006

Quiescent deformation of the Aniakchak Caldera, Alaska mapped by InSAR

The 10-km-wide caldera of the historically active Aniakchak volcano, Alaska, subsides ∼13 mm/yr, based on data from 19 European Remote Sensing Satellite (ERS-1 and ERS-2) interferometric synthetic aperture radar (InSAR) images from 1992 through 2002. The pattern of subsidence does not reflect the distribution of pyroclastic deposits from the last eruption in 1931 and therefore is not related to compaction of fragmental debris. Weighted least-squares inversion of the deformation maps indicates a relatively constant subsidence rate. Modeling the deformation with a Mogi point source locates the source of subsidence at ∼4 km below the central caldera floor, which is consistent with the inferred depth of magma storage before the 1931 eruption. Magmatic CO 2 and He have been measured at a warm soda spring within the caldera, and several sub-boiling fumaroles persist elsewhere in the caldera. These observations suggest that recent subsidence can be explained by the cooling or degassing of a shallow magma body (∼4 km deep), and/or the reduction of the pore-fluid pressure of a cooling hydrothermal system. Ongoing deformation of the volcano detected by InSAR, in combination with magmatic gas output from at least one warm spring, and infrequent low-level bursts of seismicity below the caldera, indicate that the volcanic system is still active and requires close attention for the timely detection of possible hazards.

Alaska↗
USGS2006

Interferometric synthetic aperture radar (InSAR) and its applications to study volcanoes, part 2: InSAR imaging of Alaskan Volcanoes

Interferometric synthetic aperture radar (InSAR) is a remote sensing technique which can measure ground surface deformation with sub-centimeter precision and spatial resolution in tens-of-meters over a large region. This paper summarizes our recent InSAR studies of Alaskan volcanoes, associated with both eruptive and non-eruptive activity. It shows that InSAR can improve our understanding of how the Alaskan volcanoes work and enhance our capability to predict future eruptions and the associated hazards.

Science of Surveying and Mapping↗
USGS2002

Magmatic inflation at a dormant stratovolcano: 1996-1998 activity at Mount Peulik volcano, Alaska, revealed by satellite radar interferometry

A series of ERS radar interferograms that collectively span the time interval from July 1992 to August 2000 reveal that a presumed magma body located 6.6 ??? 0.5 km beneath the southwest flank of the Mount Peulik volcano inflated 0.051 ??? 0.005 km3 between October 1996 and September 1998. Peulik has been active only twice during historical time, in 1814 and 1852, and the volcano was otherwise quiescent during the 1990s. The inflation episode spanned at least several months because separate interferograms show that the associated ground deformation was progressive. The average inflation rate of the magma body was ???0.003 km3/month from October 1996 to September 1997, peaked at 0.005 km3/month from 26 June to 9 October 1997, and dropped to ???0.001 km3/month from October 1997 to September 1998. An intense earthquake swarm, including three ML 4.8 - 5.2 events, began on 8 May 1998 near Becharof Lake, ???30 km northwest of Peulik. More than 400 earthquakes with a cumulative moment of 7.15 ?? 1017 N m were recorded in the area through 19 October 1998. Although the inflation and earthquake swarm occurred at about the same time, the static stress changes that we calculated in the epicentral area due to inflation beneath Peulik appear too small to provide a causal link. The 1996-1998 inflation episode at Peulik confirms that satellite radar interferometry can be used to detect magma accumulation beneath dormant volcanoes at least several months before other signs of unrest are apparent. This application represents a first step toward understanding the eruption cycle at Peulik and other stratovolcanoes with characteristically long repose periods.

Alaska↗