Michael Lisowski
United States Geological Survey
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Nature | 2002
Peter Cervelli; Paul Segall; Kaj M. Johnson; Michael Lisowski; Asta Miklius
One of the greatest hazards associated with oceanic volcanoes is not volcanic in nature, but lies with the potential for catastrophic flank failure. Such flank failure can result in devastating tsunamis and threaten not only the immediate vicinity, but coastal cities along the entire rim of an ocean basin. Kilauea volcano on the island of Hawaii, USA, is a potential source of such flank failures and has therefore been monitored by a network of continuously recording geodetic instruments, including global positioning system (GPS) receivers, tilt meters and strain meters. Here we report that, in early November 2000, this network recorded transient southeastward displacements, which we interpret as an episode of aseismic fault slip. The duration of the event was about 36 hours, it had an equivalent moment magnitude of 5.7 and a maximum slip velocity of about 6 cm per day. Inversion of the GPS data reveals a shallow-dipping thrust fault at a depth of 4.5 km that we interpret as the down-dip extension of the Hilina Pali–Holei Pali normal fault system. This demonstrates that continuously recording geodetic networks can detect accelerating slip, potentially leading to warnings of volcanic flank collapse.
Journal of Geophysical Research | 2000
Susan M. Owen; Paul Segall; Michael Lisowski; Asta Miklius; Roger P. Denlinger; Maurice K. Sako
Campaign Global Positioning System (GPS) measurements from 1990 to 1996 are used to calculate surface displacement rates on Kilauea Volcano, Hawaii. The GPS data show that the south flank of the volcano, which has generated several large earthquakes in the past 3 decades, is displacing at up to ;8 cm/yr to the south-southeast. The summit and rift zones are subsiding, with maximum subsidence rates of ;8 cm/yr observed a few kilometers south of the summit caldera. Elastic dislocation modeling of the GPS data suggests that the active sources of deformation include deep rift opening along the upper east and east rift zone, fault slip along a subhorizontal fault near the base of the volcano, and deflation near the summit caldera. A nonlinear optimization algorithm was used to explore the parameter space and to find the best fitting source geometry. There is a broad range of model geometries that fit the data reasonably well. However, certain models can be ruled out, including those that have shallow rift opening or shallow fault slip. Some offshore, aseismic slip on a fault plane that dips between 258 north- northwest and 88 south-southeast is required. Best fitting slip and rift opening rates are 23-28 cm/yr, although rates as low as 10 cm/yr are permitted by the data.
Journal of Geophysical Research | 1997
Wayne Thatcher; Grant A. Marshall; Michael Lisowski
Data from all available triangulation networks affected by the 1906 earthquake have been combined to assess the trade-off between slip resolution and its uncertainty and to construct a conservative image of coseismic slip along the rupture. Because of varying network aperture and station density, slip resolution is very uneven. Although slip is determined within uncertainties of ±1.0 m along 60% of the fault, constraints are poor on the remaining, mostly offshore portions of the rupture. Slip decreases from maxima of 8.6 and 7.5 m at Shelter Cove and Tomales Bay to 4.5 m near Mount Tamalpais and 2.7 m at Loma Prieta. The geodetically derived slip distribution is in poor agreement with estimates based on analysis of S wave seismograms, probably because these waves register only 20–30% of the total seismic moment obtained from longer-period surface waves. Consideration of a range of fault geometries for 1906 slip near Loma Prieta indicates right-lateral motions lie between 2.3 and 3.1 m. These values are considerably greater than the 1.5 m of measured surface slip on which several assessments of high earthquake hazard for this fault segment were based. This factor, along with the absence of 1989 slippage where 1906 surface slip was used to make the forecasts, casts doubt on some claims of success in predicting the 1989 M=6.9 Loma Prieta earthquake.
Geophysical Research Letters | 2000
Susan Owen; Paul Segall; Michael Lisowski; Asta Miklius; Mark H. Murray; Michael Bevis; James Foster
A continuous Global Positioning System (GPS) network on Kilauea Volcano captured the most recent fissure eruption in Kilaueas East Rift Zone (ERZ) in unprecedented spatial and temporal detail. The short eruption drained the lava pond at Pueu Oeo, leading to a two month long pause in its on-going eruption. Models of the GPS data indicate that the intrusions bottom edge extended to only 2.4 km. Continuous GPS data reveal rift opening 8 hours prior to the eruption. Absence of precursory summit inflation rules out magma storage overpressurization as the eruptions cause. We infer that stresses in the shallow rift created by the continued deep rift dilation and slip on the south flank decollement caused the rift intrusion.
Journal of Geophysical Research | 1998
Paul T. Delaney; Roger P. Denlinger; Michael Lisowski; Asta Miklius; Paul G. Okubo; Arnold T. Okamura; Maurice K. Sako
The rift system traversing about 80 km of the subaerial surface of Kilauea volcano has extended continuously since the M 7.2 flank earthquake of November 1975. Widening across the summit has amounted to more than 250 cm, decelerating after 1975 from about 25 to 4 cm yr−1 since 1983. Concurrently, the summit has subsided more than 200 cm, even as the adjacent south flank has risen more than 50 cm. The axes of the upper zones, about 10 km from the summit, subsided before 1983 at average rates of 9 and 4 cm yr−1, respectively, and at rates of 4 and 3 cm yr−1 since. The middle southwest rift zone is also subsiding and, at the other end of Kilaueas subaerial rift system, subsidence along the lower east rift zone has averaged 1–2 cm yr−1. Deformation of Kilaueas south flank has been continuous, although subject as well to displacements caused by major rift zone seismic swarms. Whereas horizontal strains across the subaerial south flank seem to have been generally compressive after 1975, they have been extensional since about 1980 or 1981, interrupted only by the east rift zone dike intrusion of 1983. Because the magnitudes of these contractions and extensions are much less than the extension across the rift system, the subaerial south flank is apparently sliding seaward on its basal decollement more than it is accumulating horizontal strains within the overlying volcanic pile. Kilauea suffers from gravitational spreading made even more unstable by accumulation of magma along the rift system at depths in excess of about 4–5 km in the presence hot rock incapable of withstanding deviatoric stresses. This seismicly quiescent zone decouples the south flank from the rest of Hawaiis volcanic edifice; the rift zones at lesser depths exhibit a more brittle and, therefore, sporadic extensional behavior. Judging from the modern extension record of the summit, which both predates the M 7.2 earthquake of 1975 and has outlived its 10-year period of aftershocks, Kilauea will continue to spread along its rift system as its south flank slips seaward to accommodate the accretion of magma and its relatively dense olivine-rich differentiate.
Journal of Geophysical Research | 2001
Kristine M. Larson; Peter Cervelli; Michael Lisowski; Asta Miklius; Paul Segall; Susan Owen
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 Kilaueas 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/ AAA p . Values lower than this suppress small signals, and values greater than this have significantly higher noise at periods of 1-6 hours.
Journal of Geophysical Research | 1996
Mark H. Murray; Grant A. Marshall; Michael Lisowski; Ross S. Stein
We invert geodetic measurements of coseismic surface displacements to determine a dislocation model for the April 25, 1992, M = 7 Cape Mendocino, California, earthquake. The orientation of the model slip vector, which nearly parallels North America-Juan de Fuca relative plate convergence, and the location and orientation of the model fault relative to the offshore Cascadia megathrust, suggest that the 1992 Cape Mendocino earthquake is the first well-recorded event to relieve strain associated with the Cascadia subduction zone. We use data from three geodetic techniques: (1) the horizontal and vertical displacements of 13 monuments surveyed with the Global Positioning System, corrected for observed horizontal interseismic strain accumulation, (2) 88 section-elevation differences between leveling monuments, and (3) the uplift of 12 coastal sites observed from the die-off of intertidal marine organisms. Maximum observed displacements are 0.4 m of horizontal movement and 1.5 m of uplift along the coast. We use Monte Carlo techniques to estimate an optimal uniform slip rectangular fault geometry and its uncertainties. The optimal model using all the data resolves 4.9 m of slip on a 14 by 15 km fault that dips 28° SE. The fault extends from 1.5 to 8.7 km in depth and the main-shock hypocenter is close to the downdip projection of the fault. The shallowly dipping fault plane is consistent with the observed aftershock locations, and the estimated geodetic moment is 3.1 × 1019 N m, 70% of the seismic moment. Other models that exclude leveling data collected in 1935 and 1942 are more consistent with seismological estimates of the fault geometry. If the earthquake is characteristic for this segment, the estimated horizontal slip vector compared with plate convergence rates suggests a recurrence interval of 140 years, with a 95% confidence range of 100–670 years. The coseismic uplift occurred in a region that also has high Quaternary uplift rates determined from marine terrace studies. If repeated ruptures of this southernmost segment of the Cascadia megathrust are responsible for the Quaternary uplift, a comparison of the coseismic uplift with coastal uplift rates suggests a recurrence interval of 200–400 years. Thus comparing horizontal and vertical coseismic to long-term deformation suggests a recurrence interval of about 100–300 years for M = 7 events at the south end of the Cascadia megathrust.
Journal of Geophysical Research | 1996
Richard A. Snay; Michael W. Cline; C. Randolph Philipp; David D. Jackson; Yanjie Feng; Zheng-Kang Shen; Michael Lisowski
We use geodetic data spanning the 1920–1992 interval to estimate the horizontal velocity field near the big bend segment of Californias San Andreas fault (SAF). More specifically, we estimate a horizontal velocity vector for each node of a two-dimensional grid that has a 15-min-by-15-min mesh and that extends between latitudes 34.0°N and 36.0°N and longitudes 117.5°W and 120.5°W. For this estimation process, we apply bilinear interpolation to transfer crustal deformation information from geodetic sites to the grid nodes. The data include over a half century of triangulation measurements, over two decades of repeated electronic distance measurements, a decade of repeated very long baseline interferometry measurements, and several years of Global Positioning System measurements. Magnitudes for our estimated velocity vectors have formal standard errors ranging from 0.7 to 6.8 mm/yr. Our derived velocity field shows that (1) relative motion associated with the SAF exceeds 30 mm/yr and is distributed on the Earths surface across a band (>100 km wide) that is roughly centered on this fault; (2) when velocities are expressed relative to a fixed North America plate, the motion within our primary study region has a mean orientation of N44°W ± 2° and the surface trace of the SAF is congruent in shape to nearby contours of constant speed yet this trace is oriented between 5° and 10° counterclockwise relative to these contours; and (3) large strain rates (shear rates > 150 nrad/yr and/or areal dilatation rates < −150 nstr/yr) exist near the Garlock fault, near the White Wolf fault, and in the Ventura basin.
Geophysical Research Letters | 2015
Emily Montgomery-Brown; Chuck Wicks; Peter Cervelli; John Langbein; J. L. Svarc; David R. Shelly; David P. Hill; Michael Lisowski
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 × 106 m3/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.
Geophysical Research Letters | 2000
Mark H. Murray; Michael Lisowski
We combine triangulation, trilateration, and GPS observations to determine horizontal strain rates along the Cascadia subduction zone from Cape Mendocino to the Strait of Juan de Fuca. Shear-strain rates are significantly greater than zero (95% confidence) in all forearc regions (26–167 nanoradians/yr), and are not significant in the arc and backarc regions. The deformation is primarily uniaxial contraction nearly parallel to Juan de Fuca-North America plate convergence (N55°–80°E). The strain rates are consistent with an elastic dislocation model for interseismic slip with a shallow 100-km wide locked zone and a deeper 75-km transition zone along the entire megathrust, except along the central Oregon coast where relatively lower strain rates are consistent with 30–40 km wide locked and transition zones.