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University of Missouri-Columbia
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- PublicationRestrictedDeep crustal roots beneath the northern Apennines inferred from teleseismic receiver functions(2003)
; ; ;Mele, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Sandvol, E.; University of Missouri-Columbia; Teleseismic waveforms recorded by a regional array crossing the northern Italian peninsula and northern Corsica are analyzed using the receiver function technique, to determine the first order crustal structure. The receiver function approach is used to isolate receiver-side PS conversions generated at the crust-mantle boundary and any major velocity discontinuity beneath the stations. We used the time delay between the direct P wave and the PS wave converted at the Moho discontinuity to infer crustal thickness beneath the stations. The crust-mantle boundary is estimated at 25 ± 1 km of depth in northern Corsica, 20 ± 2 km beneath the Elba island and 20 to 24 ± 2 km beneath Tuscany. In the eastern portion of the array, Moho depth increases from 28 ± 2 km beneath the Adriatic coast to 49 ± 3 km beneath the Apennine chain, in a distance of about 100 km. A double PS conversion produced beneath the Val Tiberina graben, to the west of the Apennines, corresponds to interfaces as deep as 20 ± 2 and 52 ± 2 km. This observation supports the hypothesis of partial overlapping between the shallow Tuscan Moho and the deeper Adriatic Moho. The westward deepening of the Adriatic Moho beneath the northern Apennines can be explained by lithosphere delamination that has dragged downward the Adriatic lower crust. The deep crustal root estimated beneath the northern Apennines indicates that this portion of the chain is isostatically overcompensated.459 67 - PublicationRestrictedEvidence of crustal thickening beneath the central Apennines (Italy) from teleseismic receiver functions(2006)
; ; ; ;Mele, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Sandvol, E.; Department of Geological Sciences, University of Missouri-Columbia, Columbia, MO 65201, USA ;Cavinato, G. P.; CNR-Istituto di Geologia Ambientale e Geoingegneria, Dipartimento di Scienze della Terra, Università di Roma “La Sapienza”; ; We computed receiver functions of teleseismic events that occurred within a distance of 35–90° and were recorded in central Italy by 15 temporary stations and 1 permanent station. In the receiver functions we identified the P-to-S phase converted at the Moho discontinuity beneath each station and estimated crustal thickness from the time delay of this phase with respect to the direct P arrival. For the temporary stations this relatively simple approach is justified given their limited recording period. To the permanent station we also applied the slant stacking technique to try to constrain the bulk crustal Vp/Vs and validate our estimate of crustal thickness. Our results show that, in central Italy, the Moho is shallow (∼22 km) beneath the Tyrrhenian margin of the peninsula and deepens toward the east. Beneath the central Apennines, Moho depth ranges from 39 to 47 km. The thickest crust matches the highest topography. At the Tremiti islands, in the Adriatic Sea, crustal thickness is 33 km. While our Moho depths beneath the Tyrrhenian side of the peninsula and the Adriatic Sea are in agreement with previous results, a new result of this study is the crustal thickening beneath the central Apennines. This leads to the conclusion that the central Apennine topography is supported by a significant crustal root.280 24 - PublicationOpen AccessCrustal and uppermost mantle shear wave velocity structure beneath the Middle East from surface wave tomography(2020-05)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; We have constructed a 3-D shear wave velocity (Vs) model for the crust and uppermost mantle beneath the Middle East using Rayleigh wave records obtained from ambient-noise cross-correlations and regional earthquakes. We combined one decade of data collected from 852 permanent and temporary broad-band stations in the region to calculate group-velocity dispersion curves. A compilation of >54 000 ray paths provides reliable group-velocity measurements for periods between 2 and 150 s. Path-averaged group velocities calculated at different periods were inverted for 2-D group-velocity maps. To overcome the problem of heterogeneous ray coverage, we used an adaptive grid parametrization for the group-velocity tomographic inversion. We then sample the period-dependent group-velocity field at each cell of a predefined grid to generate 1-D group-velocity dispersion curves, which are subsequently inverted for 1-D Vs models beneath each cell and combined to approximate the 3-D Vs structure of the area. The Vs model shows low velocities at shallow depths (5–10 km) beneath the Mesopotamian foredeep, South Caspian Basin, eastern Mediterranean and the Black Sea, in coincidence with deep sedimentary basins. Shallow high-velocity anomalies are observed in regions such as the Arabian Shield, Anatolian Plateau and Central Iran, which are dominated by widespread magmatic exposures. In the 10–20 km depth range, we find evidence for a band of high velocities (>4.0 km s–1) along the southern Red Sea and Arabian Shield, indicating the presence of upper mantle rocks. Our 3-D velocity model exhibits high velocities in the depth range of 30–50 km beneath western Arabia, eastern Mediterranean, Central Iranian Block, South Caspian Basin and the Black Sea, possibly indicating a relatively thin crust. In contrast, the Zagros mountain range, the Sanandaj-Sirjan metamorphic zone in western central Iran, the easternmost Anatolian plateau and Lesser Caucasus are characterized by low velocities at these depths. Some of these anomalies may be related to thick crustal roots that support the high topography of these regions. In the upper mantle depth range, high-velocity anomalies are obtained beneath the Arabian Platform, southern Zagros, Persian Gulf and the eastern Mediterranean, in contrast to low velocities beneath the Red Sea, Arabian Shield, Afar depression, eastern Turkey and Lut Block in eastern Iran. Our Vs model may be used as a new reference crustal model for the Middle East in a broad range of future studies.73 42