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Abstract The crustal structure in south‐central Alaska has been influenced by terrane accretion, flat slab subduction, and a modern strike‐slip fault system. Within the active subduction system, the presence of the Denali Volcanic Gap (DVG), a ∼400 km region separating the active volcanism of the Aleutian Arc to the west and the Wrangell volcanoes to the east, remains enigmatic. To better understand the regional tectonics and the nature of the volcanic gap, we deployed a month‐long north‐south linear geophone array of 306 stations with an interstation distance of 1 km across the Alaska Range. By calculating multi‐component noise cross‐correlation and jointly inverting Rayleigh wave phase velocity and ellipticity across the array, we construct a 2‐D shear wave velocity model along the transect down to ∼16 km depth. In the shallow crust, we observe low‐velocity structures associated with sedimentary basins and image the Denali fault as a narrow localized low‐velocity anomaly extending to at least 12 km depth. About 12 km, below the fold and thrust fault system in the northern flank of the Alaska Range, we observe a prominent low‐velocity zone with more than 15% velocity reduction. Our velocity model is consistent with known geological features and reveals a previously unknown low‐velocity zone that we interpret as a magmatic feature. Based on this feature's spatial relationship to the Buzzard Creek and Jumbo Dome volcanoes and the location above the subducting Pacific Plate, we interpret the low‐velocity zone as a previously unknown subduction‐related crustal magma reservoir located beneath the DVG.
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Crustal structure variations in south-central Mexico from receiver functions
Summary Mexico has a complex geological history that is typified by the distinctive terranes that are found in the south-central region. Crustal thickness variations often correlate with geological terranes that have been altered by several processes in the past, for example aerial or subduction erosion, underplating volcanic material or rifting but few geophysical studies have locally imaged the entire continental crust in Mexico. In this paper, the thickness of three layers of the crust in south-central Mexico is determined. To do this, we use P- and S-wave receiver functions (RF) from 159 seismological broad-band stations. Thanks to its adaptive nature, we use an empirical mode decomposition (EMD) algorithm to reconstruct the RFs into intrinsic mode functions (IMF) in order to enhance the pulses related to internal discontinuities within the crust. To inspect possible lateral variations, the RFs are grouped into quadrants of 90°, and their amplitudes are mapped into the thickness assuming a three-layer model. Using this approach, we identify a shallow sedimentary layer with a thickness in the range of 1–4 km. The upper-crust was estimated to be of a few kilometers (<10 km) thick near the Pacific coast, and thicker, approximately 15 km in central Oaxaca and under the Trans-Mexican Volcanic Belt (TMVB). Close to the Pacific coast, we infer a thin crust of approximately 16 ± 0.9 km, while in central Oaxaca and beneath the TMVB, we observe a thicker crust ranging between 30 and 50 km ± 2.0 km. We observe a crustal thinning, of approximately 6 km, from central Oaxaca (37 ± 1.9 km) towards the Gulf of Mexico, under the Veracruz Basin, where we estimate a crustal thickness of 31.6 ± 1.9 km. The boundary between the upper and lower crust in comparison with the surface of the Moho do not show significant variations other than the depth difference. We observe small crustal variations across the different terranes on the study area, with the thinnest crust located at the Pacific coast and Gulf of Mexico coast. The thickest crust is estimated to be in central Oaxaca and beneath the TMVB.
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- Award ID(s):
- 1645063
- PAR ID:
- 10121955
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Geophysical Journal International
- Volume:
- 219
- Issue:
- 3
- ISSN:
- 0956-540X
- Page Range / eLocation ID:
- p. 2174-2186
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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