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Insights on the upper mantle beneath the Eastern Alps.

Bianchi I, Miller MS, Bokelmann G - Earth Planet. Sci. Lett. (2014)

Bottom Line: Analyses of Ps and Sp receiver functions from datasets collected by permanent and temporary seismic stations, image a seismic discontinuity, due to a negative velocity contrast across the entire Eastern Alps.The receiver functions show the presence of the discontinuity within the upper mantle with a resolution of tens of kilometers laterally.Comparison with previous studies renders it likely that the observed discontinuity coincides with the lithosphere-asthenosphere boundary (LAB) east of 15°E longitude, while it could be associated with a low velocity zone west of 15°E.

View Article: PubMed Central - PubMed

Affiliation: Institut für Meteorologie und Geophysik, Universität Wien, Althanstraße 14 (UZA II), 1090 Vienna, Austria.

ABSTRACT

Analyses of Ps and Sp receiver functions from datasets collected by permanent and temporary seismic stations, image a seismic discontinuity, due to a negative velocity contrast across the entire Eastern Alps. The receiver functions show the presence of the discontinuity within the upper mantle with a resolution of tens of kilometers laterally. It is deeper (100-130 km) below the central portion of the Eastern Alps, and shallower (70-80 km) towards the Pannonian Basin and in the Central Alps. Comparison with previous studies renders it likely that the observed discontinuity coincides with the lithosphere-asthenosphere boundary (LAB) east of 15°E longitude, while it could be associated with a low velocity zone west of 15°E.

No MeSH data available.


Related in: MedlinePlus

PRF common-conversion-point (CCP) profiles migrated at 100 km depth along profiles AA′, BB′ and CC′, PRF are computed with a frequency cut off of 0.2 Hz (see Figs. 1 and 9 for locations). The discontinuity contribution is highlighted thanks to the depth migration: green stars for depth from the SRFs at adjacent stations. Yellow stars indicate the interpreted discontinuity depths from the PRFs. Blue and red dashed lines mark the arrival times of the Moho phase (Psm) and its multiples (PpPs and PsPs + PpSs), black dashed lines mark the arrival times of the intracrustal phase and its multiples, as in Fig. 3. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
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fg0070: PRF common-conversion-point (CCP) profiles migrated at 100 km depth along profiles AA′, BB′ and CC′, PRF are computed with a frequency cut off of 0.2 Hz (see Figs. 1 and 9 for locations). The discontinuity contribution is highlighted thanks to the depth migration: green stars for depth from the SRFs at adjacent stations. Yellow stars indicate the interpreted discontinuity depths from the PRFs. Blue and red dashed lines mark the arrival times of the Moho phase (Psm) and its multiples (PpPs and PsPs + PpSs), black dashed lines mark the arrival times of the intracrustal phase and its multiples, as in Fig. 3. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Mentions: Using both SRF and PRF analyses, we detect a negative impedance contrast generated by a discontinuity in the upper mantle. Results from the PRFs are analyzed along three CCP profiles migrated at 100 km depth (Fig. 7). The closely located TRANSALP RF profile, at longitude (Kummerow et al., 2004) suggests the Moho multiples obliterate the shallow part of the mantle, not allowing the detection of the LAB or low velocities layers. We display arrival times of the Moho phase and its multiples in Fig. 7. The marked phases and multiples predicted arrival times have been extracted from profiles AA′, BB′ and CC′ migrated at 40 km depth (Fig. 3). The negative phase that we interpret in this study is marked in Fig. 7 with yellow stars and arrives with a delay time in between the Psm and its multiples. At 200–240 km within AA′, 150–200 km within BB′ and 100–120 km within CC′, the negative multiples (PsPs + PpSs) merge with the converted phase, broadening the phase due to the velocity decrease. The discontinuity retrieved depths from single stations SRF analysis are strongly coincident with depths estimated from the PRFs although some scattering in the results is observed at the crossing between AA′ and BB′. This may be due to the location of the piercing points of the events used to compute the SRF. Indeed the conversions do not happen beneath the stations but at some distance away, therefore the rays might sample different structures. In the Southern Alps, stations MYKA, ACOM, VINO detect the discontinuity at a depth of which are comparable to the depths estimated by the PRFs for the southern part of the AA′ transect (see Fig. 7a). The discontinuity depth estimates based on the SRFs at the stations MYKA, ACOM, KBA, MOA and KRUC also correspond to the estimated depths from PRFs along profile BB′ (Fig. 7b). Strong agreement among the results is observed for the easternmost area, where the discontinuity depth values for station ARSA and CONA are also extremely consistent to the shallow depth estimates from the PRFs obtained for the south-eastern part of the CC′ profile (Fig. 7c). In the SRF profiles shown in Fig. 4 there is a deepening of the discontinuity signal in the central part of profile DD′ (ABTA to OBKA), and a nearly flat ( deep) discontinuity in the western part of the EE′ profile, followed by an abrupt shallowing at the easternmost edge (stations PERS-GROS).


Insights on the upper mantle beneath the Eastern Alps.

Bianchi I, Miller MS, Bokelmann G - Earth Planet. Sci. Lett. (2014)

PRF common-conversion-point (CCP) profiles migrated at 100 km depth along profiles AA′, BB′ and CC′, PRF are computed with a frequency cut off of 0.2 Hz (see Figs. 1 and 9 for locations). The discontinuity contribution is highlighted thanks to the depth migration: green stars for depth from the SRFs at adjacent stations. Yellow stars indicate the interpreted discontinuity depths from the PRFs. Blue and red dashed lines mark the arrival times of the Moho phase (Psm) and its multiples (PpPs and PsPs + PpSs), black dashed lines mark the arrival times of the intracrustal phase and its multiples, as in Fig. 3. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4375711&req=5

fg0070: PRF common-conversion-point (CCP) profiles migrated at 100 km depth along profiles AA′, BB′ and CC′, PRF are computed with a frequency cut off of 0.2 Hz (see Figs. 1 and 9 for locations). The discontinuity contribution is highlighted thanks to the depth migration: green stars for depth from the SRFs at adjacent stations. Yellow stars indicate the interpreted discontinuity depths from the PRFs. Blue and red dashed lines mark the arrival times of the Moho phase (Psm) and its multiples (PpPs and PsPs + PpSs), black dashed lines mark the arrival times of the intracrustal phase and its multiples, as in Fig. 3. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Mentions: Using both SRF and PRF analyses, we detect a negative impedance contrast generated by a discontinuity in the upper mantle. Results from the PRFs are analyzed along three CCP profiles migrated at 100 km depth (Fig. 7). The closely located TRANSALP RF profile, at longitude (Kummerow et al., 2004) suggests the Moho multiples obliterate the shallow part of the mantle, not allowing the detection of the LAB or low velocities layers. We display arrival times of the Moho phase and its multiples in Fig. 7. The marked phases and multiples predicted arrival times have been extracted from profiles AA′, BB′ and CC′ migrated at 40 km depth (Fig. 3). The negative phase that we interpret in this study is marked in Fig. 7 with yellow stars and arrives with a delay time in between the Psm and its multiples. At 200–240 km within AA′, 150–200 km within BB′ and 100–120 km within CC′, the negative multiples (PsPs + PpSs) merge with the converted phase, broadening the phase due to the velocity decrease. The discontinuity retrieved depths from single stations SRF analysis are strongly coincident with depths estimated from the PRFs although some scattering in the results is observed at the crossing between AA′ and BB′. This may be due to the location of the piercing points of the events used to compute the SRF. Indeed the conversions do not happen beneath the stations but at some distance away, therefore the rays might sample different structures. In the Southern Alps, stations MYKA, ACOM, VINO detect the discontinuity at a depth of which are comparable to the depths estimated by the PRFs for the southern part of the AA′ transect (see Fig. 7a). The discontinuity depth estimates based on the SRFs at the stations MYKA, ACOM, KBA, MOA and KRUC also correspond to the estimated depths from PRFs along profile BB′ (Fig. 7b). Strong agreement among the results is observed for the easternmost area, where the discontinuity depth values for station ARSA and CONA are also extremely consistent to the shallow depth estimates from the PRFs obtained for the south-eastern part of the CC′ profile (Fig. 7c). In the SRF profiles shown in Fig. 4 there is a deepening of the discontinuity signal in the central part of profile DD′ (ABTA to OBKA), and a nearly flat ( deep) discontinuity in the western part of the EE′ profile, followed by an abrupt shallowing at the easternmost edge (stations PERS-GROS).

Bottom Line: Analyses of Ps and Sp receiver functions from datasets collected by permanent and temporary seismic stations, image a seismic discontinuity, due to a negative velocity contrast across the entire Eastern Alps.The receiver functions show the presence of the discontinuity within the upper mantle with a resolution of tens of kilometers laterally.Comparison with previous studies renders it likely that the observed discontinuity coincides with the lithosphere-asthenosphere boundary (LAB) east of 15°E longitude, while it could be associated with a low velocity zone west of 15°E.

View Article: PubMed Central - PubMed

Affiliation: Institut für Meteorologie und Geophysik, Universität Wien, Althanstraße 14 (UZA II), 1090 Vienna, Austria.

ABSTRACT

Analyses of Ps and Sp receiver functions from datasets collected by permanent and temporary seismic stations, image a seismic discontinuity, due to a negative velocity contrast across the entire Eastern Alps. The receiver functions show the presence of the discontinuity within the upper mantle with a resolution of tens of kilometers laterally. It is deeper (100-130 km) below the central portion of the Eastern Alps, and shallower (70-80 km) towards the Pannonian Basin and in the Central Alps. Comparison with previous studies renders it likely that the observed discontinuity coincides with the lithosphere-asthenosphere boundary (LAB) east of 15°E longitude, while it could be associated with a low velocity zone west of 15°E.

No MeSH data available.


Related in: MedlinePlus