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Results for “Journal of Geophysical Research- Solid Earth”

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At least 433 records · Page 24Linked to original sources
USGS2002

Carbon dioxide emission rate of Kīlauea Volcano: Implications for primary magma and the summit reservoir

We report a CO 2 emission rate of 8500 metric tons per day (t d −1 ) for the summit of Kīlauea Volcano, several times larger than previous estimates. It is based on three sets of measurements over 4 years of synchronous SO 2 emission rates and volcanic CO 2 /SO 2 concentration ratios for the summit correlation spectrometer (COSPEC) traverse. Volcanic CO 2 /SO 2 for the traverse is representative of the global ratio for summit emissions. The summit CO 2 emission rate is nearly constant, despite large temporal variations in summit CO 2 /SO 2 and SO 2 emission rates. Summit CO 2 emissions comprise most of Kīlauea's total CO 2 output (∼9000 t d −1 ). The bulk CO 2 content of primary magma determined from CO 2 emission and magma supply rate data is ∼0.70 wt %. Most of the CO 2 is present as exsolved vapor at summit reservoir depths, making the primary magma strongly buoyant. Turbulent mixing with resident reservoir magma, however, prevents frequent eruptions of buoyant primary magma in the summit region. CO 2 emissions confirm that the magma supply enters the edifice through the summit reservoir. A persistent several hundred parts per million CO 2 anomaly arises from the entry of magma into the summit reservoir beneath a square kilometer area east of Halemaumau pit crater. Since most of the CO 2 in primary magma is degassed in the summit, the summit CO 2 emission rate is an effective proxy for the magma supply rate. Both scrubbing of SO 2 and solubility controls on CO 2 and S in basaltic melt cause high CO 2 /SO 2 in summit emissions and spatially uncorrelated distributions of CO 2 and SO 2 in the summit plume.

Journal of Geophysical Research B: Solid Earth↗
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↗
USGS2002

Topographic stress perturbations in southern Davis Mountains, west Texas 1. Polarity reversal of principal stresses

We have applied a previously developed analytical stress model to interpret subsurface stress conditions inferred from acoustic televiewer logs obtained in two municipal water wells located in a valley in the southern Davis Mountains near Alpine, Texas. The appearance of stress-induced breakouts with orientations that shift by 90° at two different depths in one of the wells is explained by results from exact solutions for the effects of valleys on gravity and tectonically induced subsurface stresses. The theoretical results demonstrate that above a reference depth termed the hinge point, a location that is dependent on Poisson's ratio, valley shape, and magnitude of the maximum horizontal tectonic stress normal to the long axis of the valley, horizontal stresses parallel to the valley axis are greater than those normal to it. At depths below this hinge point the situation reverses and horizontal stresses normal to the valley axis are greater than those parallel to it. Application of the theoretical model at Alpine is accommodated by the fact that nearby earthquake focal mechanisms establish an extensional stress regime with the regional maximum horizontal principal stress aligned perpendicular to the valley axis. We conclude that the localized stress field associated with a valley setting can be highly variable and that breakouts need to be examined in this context when estimating the orientations and magnitudes of regional principal stresses.

Texas↗
USGS2002

Topographic stress perturbations in southern Davis Mountains, west Texas 2. Hydrogeologic implications

As part of a regional groundwater investigation, geophysical logs were obtained in two municipal water wells located near the west Texas city of Alpine. These boreholes are 252 and 285 m deep and penetrate extrusive rocks of Tertiary age. The deeper well was drilled in the central valley and the other along the northern flank of an east-west trending valley-ridge setting. Analysis and interpretation of the logs reveal that the two wells are subjected to significantly different stress environments because of topographic effects and exhibit significantly different hydrogeologic properties. Water production is associated with two specific types of features common to both wells: (1) the upper and lower contacts of a dense trachyte unit located in the shallow part of the wells and (2) deeper zones of highly fractured rocks within the interior of a basalt formation. The transmissivity of the trachyte boundaries is twice as large in the central valley well as it is in the ridge flank well, whereas the transmissivity of the deeper basalts is an order of magnitude greater in the flank well than it is in the central well. This discrepancy is examined from the perspective of rock failure, fracture opening, and flow enhancement by computing values for a Drucker-Prager stability factor that is based on the magnitudes of the normal and deviatoric stress invariants as a function of depth. Thus the field measurements and subsequent stress analysis offer evidence of a coupled tectonic-hydrologic interaction at this site.

Texas↗
USGS2002

A Holocene paleosecular variation from 14C-dated volcanic rocks in western North America

A paleosecular variation (PSV) curve for western North America is presented on the basis of 94 virtual geomagnetic poles (VGPs) from dated volcanic rocks sampled at 446 sites. Approximately 60% of the paleomagnetic database has been previously published. A curve defined by “spherical smoothed splines” is fitted to the VGPs, ranked by the quality of the age determinations, where the data density is highest between 3690 and −30 years before present (B.P.) (A.D. 1950), between 7800 and 7050 years B.P., and between 14,060 and 12,700 years B.P. The younger segments of the curve derived from volcanic rocks are similar but less complex than other high-resolution PSV curves derived from lacustrine sediments, particularly the record at Fish Lake, Oregon. The PSV record from lava flows (PSVL), however, is perhaps more reliable in its general shape and chronology because of the higher fidelity of volcanic rocks as magnetic field recorders and because of the greater density of 14 C dates. The new PSVL record provides a partial Holocene master curve for western North America and will be of particular value in dating geological and archeological materials using paleomagnetic directions.

Arizona, California, Colorado, Idaho, New Mexico, ↗
USGS2003

The crustal structure from the Altai Mountains to the Altyn Tagh fault, northwest China

[1] We present a new crustal section across northwest China based on a seismic refraction profile and geologic mapping. The 1100‐km‐long section crosses the southern margin of the Chinese Altai Mountains, Junggar Accretional Belt and eastern Junggar basin, easternmost Tianshan Mountains, and easternmost Tarim basin. The crustal velocity structure and Poisson's ratio (σ), which provide a constraint on crustal composition, were determined from P and S wave data. Despite the complex geology, the crustal thickness along the entire profile is nearly uniform at 50 km. The thickest crust (56 km) occurs at the northern end of the profile beneath the Altai Mountains and the thinnest (46 km) crust is beneath the Junggar basin. Beneath surficial sediments, the crust is found to have three layers with P wave velocities ( V p ) of 6.0–6.3, 6.3–6.6, and 6.9–7.0 km/s, respectively. The southern half of the profile, including the eastern Tianshan Mountains and eastern margin of the Tarim basin, shows low P wave velocities and σ = 0.25 to a depth of 30 km, which suggests a quartz‐rich, granitic upper crustal composition. The northern half of the profile below the Altai Mountains and Junggar Accretional Belt has a higher Poisson's ratio of σ = 0.26–0.27 to a depth of 30 km, indicative of an intermediate crustal composition. The entire 1100‐km‐long profile is underlain by a 15–30 km thick high velocity (6.9–7.0 km/s; σ = 0.26–0.28) lower‐crustal layer that we interpret to have a bulk composition of mafic granulite. At the southern end of the profile, a 5‐km‐thick midcrustal low‐velocity layer ( V p = 5.9 km/s, σ = 0.25) underlies the Tianshan and the region to the south, and may be indicative of a near‐horizontal detachment interface. P n velocities are ∼7.7–7.8 km/s between the Tianshan and the Junggar basin, and ∼7.9–8.0 km/s below the Altai Mountains and eastern margin of the Tarim basin. We interpret the consistent three‐layer stratification of the crust to indicate that the crust has undergone partial melting and differentiation after Paleozoic terrane accretion. The thickness (50 km) of the crust appears to be related to compression resulting from the Indo‐Asian collision.

Altai Mountains↗
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↗
USGS2002

Strain accumulation and rotation in western Oregon and southwestern Washington

Velocities of 75 geodetic monuments in western Oregon and southwestern Washington extending from the coast to more than 300 km inland have been determined from GPS surveys over the interval 1992–2000. The average standard deviation in each of the horizontal velocity components is ∼1 mm yr −1 . The observed velocity field is approximated by a combination of rigid rotation (Euler vector relative to interior North America: 43.40°N ± 0.14°, 119.33°W ± 0.28°, and 0.822 ± 0.057° Myr −1 clockwise; quoted uncertainties are standard deviations), uniform regional strain rate (ε EE = −7.4 ± 1.8, ε EN = −3.4 ± 1.0, and ε NN = −5.0 ± 0.8 nstrain yr −1 , extension reckoned positive), and a dislocation model representing subduction of the Juan de Fuca plate beneath North America. Subduction south of 44.5°N was represented by a 40‐km‐wide locked thrust and subduction north of 44.5°N by a 75‐km‐wide locked thrust.

Oregon, Washington↗
USGS2002

High-resolution image of Calaveras Fault seismicity

By measuring relative earthquake arrival times using waveform cross correlation and locating earthquakes using the double difference technique, we are able to reduce hypocentral errors by 1 to 2 orders of magnitude over routine locations for nearly 8000 events along a 35-km section of the Calaveras Fault. This represents ∼92% of all seismicity since 1984 and includes the rupture zone of the M 6.2 1984 Morgan Hill, California, earthquake. The relocated seismicity forms highly organized structures that were previously obscured by location errors. There are abundant repeating earthquake sequences as well as linear clusters of earthquakes. Large voids in seismicity appear with dimensions of kilometers that have been aseismic over the 30-year time interval, suggesting that these portions of the fault are either locked or creeping. The area of greatest slip in the Morgan Hill main shock coincides with the most prominent of these voids, suggesting that this part of the fault may be locked between large earthquakes. We find that the Calaveras Fault at depth is extremely thin, with an average upper bound on fault zone width of 75 m. Given the location error, however, this width is not resolvably different from zero. The relocations reveal active secondary faults, which we use to solve for the stress field in the immediate vicinity of the Calaveras Fault. We find that the maximum compressive stress is at a high angle, only 13° from the fault normal, supporting previous interpretations that this fault is weak.

California↗
USGS2002

Crustal structure and relocated earthquakes in the Puget Lowland, Washington, from high-resolution seismic tomography

The availability of regional earthquake data from the Pacific Northwest Seismograph Network (PNSN), together with active source data from the Seismic Hazards Investigation in Puget Sound (SHIPS) seismic experiments, has allowed us to construct a new high-resolution 3-D, P wave velocity model of the crust to a depth of about 30 km in the central Puget Lowland. In our method, earthquake hypocenters and velocity model are jointly coupled in a fully nonlinear tomographic inversion. Active source data constrain the upper 10–15 km of the model, and earthquakes constrain the deepest portion of the model. A number of sedimentary basins are imaged, including the previously unrecognized Muckleshoot basin, and the previously incompletely defined Possession and Sequim basins. Various features of the shallow crust are imaged in detail and their structural transitions to the mid and lower crust are revealed. These include the Tacoma basin and fault zone, the Seattle basin and fault zone, the Seattle and Port Ludlow velocity highs, the Port Townsend basin, the Kingston Arch, and the Crescent basement, which is arched beneath the Lowland from its surface exposure in the eastern Olympics. Strong lateral velocity gradients, consistent with the existence of previously inferred faults, are observed, bounding the southern Port Townsend basin, the western edge of the Seattle basin beneath Dabob Bay, and portions of the Port Ludlow velocity high and the Tacoma basin. Significant velocity gradients are not observed across the southern Whidbey Island fault, the Lofall fault, or along most of the inferred location of the Hood Canal fault. Using improved earthquake locations resulting from our inversion, we determined focal mechanisms for a number of the best recorded earthquakes in the data set, revealing a complex pattern of deformation dominated by general arc-parallel regional tectonic compression. Most earthquakes occur in the basement rocks inferred to be the lower Tertiary Crescent formation. The sedimentary basins and the eastern part of the Olympic subduction complex are largely devoid of earthquakes. Clear association of hypocenters and focal mechanisms with previously mapped or proposed faults is difficult; however, seismicity, structure, and focal mechanisms associated with the Seattle fault zone suggest a possible high-angle mode of deformation with the north side up. We suggest that this deformation may be driven by isostatic readjustment of the Seattle basin.

Washington↗
USGS2002

Prehistoric ruptures of the Gurvan Bulag fault, Gobi Altay, Mongolia

The 1957 Gobi Altay M8.3 earthquake in southern Mongolia was associated with the simultaneous rupture of several faults, including the Gurvan Bulag reverse fault, which is located about 25 km south of the main strike-slip Bogd fault. Our study of paleoseismic excavations across the Gurvan Bulag fault suggests that the penultimate surface rupture occurred after 6.0 ka, most likely between 2.6 and 4.4 ka, and a possible earlier rupture occurred after 7.3 ka. Our interpretation of the stratigraphic relations in one of the exposures suggests that at least five earthquakes have generated surface rupture of the Gurvan Bulag fault since the abandonment of an ancient alluvial fan surface. Luminescence dating of sediment associated with this surface indicates that it formed either 26.6 ± 2.1 ka or 16.1 ± 2.0 ka. These data imply that the recurrence intervals for surface faulting on the Gurvan Bulag and Bogd faults are similar, on the order of several thousands of years, but that the penultimate surface ruptures of the two faults did not occur during the same earthquake.

Gobi Altay↗
USGS2002

Preeruptive inflation and surface interferometric coherence characteristics revealed by satellite radar interferometry at Makushin Volcano, Alaska: 1993-2000

Pilot reports in January 1995 and geologic field observations from the summer of 1996 indicate that a relatively small explosive eruption of Makushin, one of the more frequently active volcanoes in the Aleutian arc of Alaska, occurred on 30 January 1995. Several independent radar interferograms that each span the time period from October 1993 to September 1995 show evidence of ???7 cm of uplift centered on the volcano's east flank, which we interpret as preeruptive inflation of a ???7-km-deep magma source (??V = 0.022 km3). Subsequent interferograms for 1995-2000, a period that included no reported eruptive activity, show no evidence of additional ground deformation. Interferometric coherence at C band is found to persist for 3 years or more on lava flow and other rocky surfaces covered with short grass and sparsely distributed tall grass and for at least 1 year on most pyroclastic deposits. On lava flow and rocky surfaces with dense tall grass and on alluvium, coherence lasts for a few months. Snow and ice surfaces lose coherence within a few days. This extended timeframe of coherence over a variety of surface materials makes C band radar interferometry an effective tool for studying volcano deformation in Alaska and other similar high-latitude regions.

Journal of Geophysical Research B: Solid Earth↗
USGS2002

Undrained poroelastic response of sandstones to deviatoric stress change

Deformation of porous crustal rock through diagenesis, tectonic loading, or other processes can change pore volume and affect fluid pressure. The largest stress-induced pore pressure changes occur when fluid is trapped in pores in an “undrained” condition. We have measured the undrained poroelastic response of two sandstones to changes in mean and deviatoric stress. Pore pressure was found to respond to mean stress σ m in the usual manner: Δ p = B Δσ m ( B ranging from 0.4 to 0.7), nearly independent of the ambient deviatoric stress state. However, variations in deviatoric stress (σ d = (σ 1 − σ 3 )/2) at constant mean stress were also found to induce a reversible (elastic) pore pressure response to stress levels up to and exceeding 80% failure stress (i.e., Δ p = = const.). The coefficient η became more negative with increasing deviatoric stress level in sandstone and Ottawa sand samples. That is, η represents a dilatant response where increased deviatoric stress causes a decrease in pore pressure. The poroelastic response to deviatoric stress is explained in terms of anisotropic matrix stiffening due to closure of crack-like pore space or flattening of grain contacts at high ambient stress levels and can be important in calculations of earthquake stress transfer.

Journal of Geophysical Research B: Solid Earth↗
USGS2002

Concordant paleolatitudes for Neoproterozoic ophiolitic rocks of the Trinity Complex, Klamath Mountains, California

New paleomagnetic results from the eastern Klamath Mountains of northern California show that Neoproterozoic rocks of the Trinity ophiolitic complex and overlying Middle Devonian volcanic rocks are latitudinally concordant with cratonal North America. Combining paleomagnetic data with regional geologic and faunal evidence suggests that the Trinity Complex and related terranes of the eastern Klamath plate were linked in some fashion to the North American craton throughout that time, but that distance between them may have varied considerably. A possible model that is consistent with our paleomagnetic results and the geologic evidence is that the Trinity Complex formed and migrated parallel to paleolatitude in the basin between Laurasia and Australia–East Antarctica as the Rodinian supercontinent began to break up. It then continued to move parallel to paleolatitude at least through Middle Devonian time. Although the eastern Klamath plate served as a nucleus against which more western components of the Klamath Mountains province amalgamated, the Klamath superterrane was not accreted to North America until Early Cretaceous time.

California↗
USGS2003

Importance of a stochastic distribution of floods and erosion thresholds in the bedrock river incision problem

Fluvial erosion of bedrock occurs during occasional flood events when boundary shear stress exceeds a critical threshold to initiate incision. Therefore efforts to model the evolution of topography over long timescales should include an erosion threshold and should be driven by a stochastic distribution of erosive events. However, most bedrock incision models ignore the threshold as a second‐order detail. In addition, climate is poorly represented in most landscape evolution models, so the quantitative relationship between erosion rate and measurable climatic variables has been elusive. Here we show that the presence of an erosion threshold, when combined with a well‐constrained, probabilistic model of storm and flood occurrence, has first‐order implications for the dynamics of river incision in tectonically active areas. First, we make a direct calculation of the critical shear stress required to pluck bedrock blocks for a field site in New York. Second, we apply a recently proposed stochastic, threshold, bedrock incision model to a series of streams in California, with known tectonic and climatic forcing. Previous work in the area has identified a weak relationship between channel gradient or relief and rock uplift rate that is not easily explained by simpler detachment‐limited models. The results with the stochastic threshold model show that even low erosion thresholds, which are exceeded in steep channels during high‐frequency flood events, fundamentally affect the predicted relationship between gradient and uplift rate in steady state rivers, in a manner consistent with the observed topography. This correspondence between theory and data is, however, nonunique; models in which a thin alluvial cover may act to inhibit channel incision in the low uplift rate zone also provide plausible explanations for the observed topography. Third, we explore the broader implications of the stochastic threshold model to the development of fluvial topography in active tectonic settings. We suggest that continued field applications of geomorphic models, including physically meaningful thresholds and stochastic climate distributions, are required to advance our knowledge of interactions among surficial, climatic, and crustal processes.

California↗
USGS2002

Waveform inversion of oscillatory signatures in long-period events beneath volcanoes

The source mechanism of long-period (LP) events is examined using synthetic waveforms generated by the acoustic resonance of a fluid-filled crack. We perform a series of numerical tests in which the oscillatory signatures of synthetic LP waveforms are used to determine the source time functions of the six moment tensor components from waveform inversions assuming a point source. The results indicate that the moment tensor representation is valid for the odd modes of crack resonance with wavelengths 2 L / n , 2 W / n , n = 3, 5, 7, …, where L and W are the crack length and width, respectively. For the even modes with wavelengths 2 L / n , 2 W / n , n = 2, 4, 6, …, a generalized source representation using higher-order tensors is required, although the efficiency of seismic waves radiated by the even modes is expected to be small. We apply the moment tensor inversion to the oscillatory signatures of an LP event observed at Kusatsu-Shirane Volcano, central Japan. Our results point to the resonance of a subhorizontal crack located a few hundred meters beneath the summit crater lakes. The present approach may be useful to quantify the source location, geometry, and force system of LP events, and opens the way for moment tensor inversions of tremor.

Journal of Geophysical Research B: Solid Earth↗
USGS2003

Slip history and dynamic implications of the 1999 Chi-Chi, Taiwan, earthquake

[1] We investigate the rupture process of the 1999 Chi‐Chi, Taiwan, earthquake using extensive near‐source observations, including three‐component velocity waveforms at 36 strong motion stations and 119 GPS measurements. A three‐plane fault geometry derived from our previous inversion using only static data [ Ji et al. , 2001 ] is applied. The slip amplitude, rake angle, rupture initiation time, and risetime function are inverted simultaneously with a recently developed finite fault inverse method that combines a wavelet transform approach with a simulated annealing algorithm [ Ji et al. , 2002b ]. The inversion results are validated by the forward prediction of an independent data set, the teleseismic P and SH ground velocities, with notable agreement. The results show that the total seismic moment release of this earthquake is 2.7 × 10 20 N m and that most of the slip occurred in a triangular‐shaped asperity involving two fault segments, which is consistent with our previous static inversion. The rupture front propagates with an average rupture velocity of ∼2.0 km s −1 , and the average slip duration (risetime) is 7.2 s. Several interesting observations related to the temporal evolution of the Chi‐Chi earthquake are also investigated, including (1) the strong effect of the sinuous fault plane of the Chelungpu fault on spatial and temporal variations in slip history, (2) the intersection of fault 1 and fault 2 not being a strong impediment to the rupture propagation, and (3) the observation that the peak slip velocity near the surface is, in general, higher than on the deeper portion of the fault plane, as predicted by dynamic modeling.

Journal of Geophysical Research B: Solid Earth↗
USGS2003

Three-dimensional velocity structure of crust and upper mantle in southwestern China and its tectonic implications

Using P and S arrival times from 4625 local and regional earthquakes recorded at 174 seismic stations and associated geophysical investigations, this paper presents a three‐dimensional crustal and upper mantle velocity structure of southwestern China (21°–34°N, 97°–105°E). Southwestern China lies in the transition zone between the uplifted Tibetan plateau to the west and the Yangtze continental platform to the east. In the upper crust a positive velocity anomaly exists in the Sichuan Basin, whereas a large‐scale negative velocity anomaly exists in the western Sichuan Plateau, consistent with the upper crustal structure under the southern Tibetan plateau. The boundary between these two anomaly zones is the Longmen Shan Fault. The negative velocity anomalies at 50‐km depth in the Tengchong volcanic area and the Panxi tectonic zone appear to be associated with temperature and composition variations in the upper mantle. The Red River Fault is the boundary between the positive and negative velocity anomalies at 50‐km depth. The overall features of the crustal and the upper mantle structures in southwestern China are a low average velocity, large crustal thickness variations, the existence of a high‐conductivity layer in the crust or/and upper mantle, and a high heat flow value. All these features are closely related to the collision between the Indian and the Asian plates.

Journal of Geophysical Research B: Solid Earth↗