Three‐dimensional <i>P</i> velocity structure of the crust below Newberry Volcano, Oregon

Stauber, Douglas A.; Green, Susan M.; Iyer, H. M.

doi:10.1029/jb093ib09p10095

Cited by 32 publications

(15 citation statements)

References 26 publications

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“…Stauber et al . [], using teleseismic tomography, recovered an anomalously high‐velocity core beneath Newberry, though this core had greater vertical extent, 10–25 km deep, than our model domain. High velocities beneath the magma body indicate that seismically‐resolvable magma conduits extending from deeper magmatic reservoirs to the magma body do not currently exist.…”

Section: Discussionmentioning

confidence: 99%

Imaging the magmatic system of Newberry Volcano using joint active source and teleseismic tomography

Heath

Hooft

Toomey

et al. 2015

Geochem Geophys Geosyst

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In this paper, we combine active and passive source P wave seismic data to tomographically image the magmatic system beneath Newberry Volcano, located east of the Cascade arc. By using both travel times from local active sources and delay times from teleseismic earthquakes recorded on closely spaced seismometers (300–800 m), we significantly improve recovery of upper crustal velocity structure (<10 km depth). The tomographic model reveals a low‐velocity feature between 3 and 5 km depth that lies beneath the caldera, consistent with a magma body. In contrast to earlier tomographic studies, where elevated temperatures were sufficient to explain the recovered low velocities, the larger amplitude low‐velocity anomalies in our joint tomography model require low degrees of partial melt (∼10%), and a minimum melt volume of ∼2.5 km3. Furthermore, synthetic tests suggest that even greater magnitude low‐velocity anomalies, and by inference larger volumes of magma (up to 8 km3), are needed to explain the observed waveform variability. The lateral extent and shape of the inferred magma body indicates that the extensional tectonic regime at Newberry influences the emplacement of magmatic intrusions. Our study shows that jointly inverting active source and passive source seismic data improves tomographic imaging of the shallow crustal seismic structure of volcanic systems and that active source experiments would benefit from longer deployment times to also record teleseismic sources.

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Section: Discussionmentioning

confidence: 99%

Imaging the magmatic system of Newberry Volcano using joint active source and teleseismic tomography

Heath

Hooft

Toomey

et al. 2015

Geochem Geophys Geosyst

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“…It has been shown that information on the velocity structure can be recovered from nodes where the diagonal resolution is low if the node is compact (Stauber et al 1988;Toomey and Foulger 1989), or if the averaging vectors or resolving kernels (rows of R) are non-zero only near 331 In the initial inversions, earthquake sources were held fixed throughout to obtain a first-order estimate of the magnitude and dimensions of velocity heterogeneity in the Aso region, and to determine the optimal velocity inversion parameters (Kong and Sudo 1993). After a preliminary velocity structure was determined, we performed inversions solving for both earthquake location and P-wave structure simultaneously, while holding the Vp/Vs ratio constant throughout the inversion.…”

Section: Solution Qualitymentioning

confidence: 99%

Three-dimensional seismic velocity structure beneath Aso Volcano, Kyushu, Japan

Sudo

Kong

2001

Bull Volcanol

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Tomographic results for P-and S-wave velocity structure beneath the active Aso Volcano, Kyushu, Japan, using 800 well-recorded earthquakes and ten shots recorded by an eight-station seismic network, are presented. A 68% variance reduction was achieved upon simultaneous inversion for hypocenter and velocity structure. Well-resolved velocity anomalies associated with the active crater reveal heterogeneity up to 26% slower and 18% faster in P velocity, and up to 31% slower and 22% faster in S velocity, than the one-dimensional model. The largest anomaly is seen over the upper 11 km in the central and northern parts beneath the central cones. Two low-velocity regions are imaged. The first region, a 10×15-km region encompassing the upper 3 km centered near the caldera wall at Tateno Valley, is characterized by P velocities up to 19% slower (20% for S). The second low-velocity region is associated with the central cones and active magma conduit system at 6 km depth. Velocities as low as 4.3 km/s (up to 26%) in P and 2 km/s (31% slower) in S characterize the 7-km-wide volume. The magma chamber is roughly spherical in shape, centered at 6 km depth, flattens at 10 km depth, and is located between Mt. Kishima, Mt. Eboshi, and Mt. Naka, the present focus of magmatism. A sharp velocity contrast at the depth of 3 km, with high velocities to the southwest and lower velocities to the northeast, characterizes different abutting structures associated with the Oita-Kumamoto Tectonic Line.

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“…In addition, the upper and middle crust beneath the volcano may be seismically attenuating, on the basis of interpretation of a seismic refraction study [Catchings, 1983]. At Newberry volcano, a shield volcano in central Oregon that is geologically similar to Medicine Lake volcano, Stauber et al [1988] used teleseismic data to image a columnar high-velocity feature that extends from within 10 km of the surface to about 25 km depth. They interpreted this feature as a largely subsolidus mafic intrusive complex.…”

Section: Crustal Structurementioning

confidence: 99%

Crustal subsidence, seismicity, and structure near Medicine Lake Volcano, California

Dzurisin¹,

Donnelly‐Nolan²,

Evans³

et al. 1991

J. Geophys. Res.

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The pattern of historical ground deformation, seismicity, and crustal structure near Medicine Lake volcano illustrates a close relation between magmatism and tectonism near the margin of the Cascade volcanic chain and the Basin and Range tectonic province. Between leveling surveys in 1954 and 1989 the summit of Medicine Lake volcano subsided 389±43 mm with respect to a reference bench mark 40 km to the southwest (average rate = 11.1±1.2 mm/yr). A smaller survey across the summit caldera in 1988 suggests that the subsidence rate was 15–28 mm/yr during 1988–1989. Swarms of shallow earthquakes (M ≤ 4.6) occurred in the region during August 1978, January–February 1981, and September 1988. Except for the 1988 swarm, which occurred beneath Medicine Lake caldera, most historical earthquakes were located at least 25 km from the summit. The spatial relation between subsidence and seismicity indicates (1) radially symmetric downwarping of the volcano's summit and flanks centered near the caldera and (2) downfaulting of the entire edifice along regional faults located 25–30 km from the summit. We propose that contemporary subsidence, seismicity, and faulting are caused by (1) loading of the crust by more than 600 km3 of erupted products plus a large volume of mafic intrusives; (2) east‐west extension in the western Basin and Range province; and, to a lesser extent, (3) crystallization or withdrawal of magma beneath the volcano. Thermal weakening of the subvolcanic crust by mafic intrusions facilitates subsidence and influences the distribution of earthquakes. Subsidence occurs mainly by aseismic creep within 25 km of the summit, where the crust has been heated and weakened by intrusions, and by normal faulting during episodic earthquake swarms in surrounding, cooler terrain.

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Three‐dimensional P velocity structure of the crust below Newberry Volcano, Oregon

Cited by 32 publications

References 26 publications

Imaging the magmatic system of Newberry Volcano using joint active source and teleseismic tomography

Imaging the magmatic system of Newberry Volcano using joint active source and teleseismic tomography

Three-dimensional seismic velocity structure beneath Aso Volcano, Kyushu, Japan

Crustal subsidence, seismicity, and structure near Medicine Lake Volcano, California

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