ALBERT

Description: P-to-S converted teleseismic waves recorded by temporary broadband networks across Tibet show a north-dipping interface that begins 50 kilometers north of the Zangbo suture at the depth of the Moho (80 kilometers) and extends to a depth of 200 kilometers beneath the Bangong suture. Under northern Tibet a segmented south-dipping structure was imaged. These observations suggest a different form of detachment of the Indian and Asian lithospheric mantles caused by differences in their composition and buoyancy.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kosarev -- Kind -- Sobolev -- Yuan -- Hanka -- Oreshin -- New York, N.Y. -- Science. 1999 Feb 26;283(5406):1306-1309.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of the Physics of the Earth, Russian Academy of Sciences, B. Gruzinskaya 10, 128810 Moscow, Russia. GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany. Freie Universitat Berlin, Geophysik, Malteser Strasse 74-100, 12249 Berlin, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10037597" target="_blank"〉PubMed〈/a〉

Description: Seismic data from central Tibet have been combined to image the subsurface structure and understand the evolution of the collision of India and Eurasia. The 410- and 660-kilometer mantle discontinuities are sharply defined, implying a lack of a subducting slab beneath the plateau. The discontinuities appear slightly deeper beneath northern Tibet, implying that the average temperature of the mantle above the transition zone is about 300 degrees C hotter in the north than in the south. There is a prominent south-dipping converter in the uppermost mantle beneath northern Tibet that might represent the top of the Eurasian mantle lithosphere underthrusting the northern margin of the plateau.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kind, R -- Yuan, X -- Saul, J -- Nelson, D -- Sobolev, S V -- Mechie, J -- Zhao, W -- Kosarev, G -- Ni, J -- Achauer, U -- Jiang, M -- New York, N.Y. -- Science. 2002 Nov 8;298(5596):1219-21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany. kind@gfz-potsdam.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12424374" target="_blank"〉PubMed〈/a〉

Description: Earthquake data collected by the INDEPTH-II Passive-Source Experiment show that there is a substantial south to north variation in the velocity structure of the crust beneath southern Tibet. North of the Zangbo suture, beneath the southern Lhasa block, a midcrustal low-velocity zone is revealed by inversion of receiver functions, Rayleigh-wave phase velocities, and modeling of the radial component of teleseismic P-waveforms. Conversely, to the south beneath the Tethyan Himalaya, no low-velocity zone was observed. The presence of the midcrustal low-velocity zone in the north implies that a partially molten layer is in the middle crust beneath the northern Yadong-Gulu rift and possibly much of southern Tibet.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kind -- Ni -- Zhao -- Wu -- Yuan -- Sandvol -- Reese -- Nabelek -- Hearn -- New York, N.Y. -- Science. 1996 Dec 6;274(5293):1692-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉R. Kind and Xiaohui Yuan, GeoForschungsZentrum Potsdam, 14473 Potsdam, Germany. James Ni, Jianxin Wu, C. Reese, T. Hearn, Department of Physics, New Mexico State University, Las Cruces, NM 88003, USA. Wenjin Zhao, Chinese Academy of Geological Sciences, Beijing, China Lianshe Zhao, Institute for Geophysics, University of Texas at Austin, Austin, TX 78759, USA. E. Sandvol, Department of Geological Sciences, Cornell University, Ithaca, NY 14853, USA. J. Nabelek, College of Oceanography, Oregon State University, Corvalis, OR 97331, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8939854" target="_blank"〉PubMed〈/a〉

Description: INDEPTH geophysical and geological observations imply that a partially molten midcrustal layer exists beneath southern Tibet. This partially molten layer has been produced by crustal thickening and behaves as a fluid on the time scale of Himalayan deformation. It is confined on the south by the structurally imbricated Indian crust underlying the Tethyan and High Himalaya and is underlain, apparently, by a stiff Indian mantle lid. The results suggest that during Neogene time the underthrusting Indian crust has acted as a plunger, displacing the molten middle crust to the north while at the same time contributing to this layer by melting and ductile flow. Viewed broadly, the Neogene evolution of the Himalaya is essentially a record of the southward extrusion of the partially molten middle crust underlying southern Tibet.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nelson -- Zhao -- Brown -- Kuo -- Che -- Liu -- Klemperer -- Makovsky -- Meissner -- Mechie -- Kind -- Wenzel -- Ni -- Nabelek -- Leshou -- Tan -- Wei -- Jones -- Booker -- Unsworth -- Kidd -- Hauck -- Alsdorf -- Ross -- Cogan -- Wu -- Sandvol -- Edwards -- New York, N.Y. -- Science. 1996 Dec 6;274(5293):1684-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉K. D. Nelson, M. Cogan, C. Wu, Department of Earth Sciences, Syracuse University, Syracuse, NY 13244, USA. W. Zhao, J. Che, X. Liu, Chinese Academy of Geological Sciences, Beijing 100037, China. L. D. Brown, M. Hauck, D. Alsdorf, A. Ross, Institute for the Study of the Continents, Cornell University, Ithaca, NY 14853, USA. J. Kuo, Lamont Doherty Geological Observatory, Palisades, NY, 10964, USA. S. L. Klemperer and Y. Makovsky, Department of Geophysics, Stanford University, Stanford, CA 94305, USA. R. Meissner, Institut fur Geophysik, Christian-Albrechts-Universitaet zu Kiel, 24098 Kiel, Germany. J. Mechie and R. Kind, GeoForschungsZentrum Potsdam (GFZ), 14473 Potsdam, Germany. F. Wenzel, Geophysikalisches Institut, Universitaet Karlsruhe, 76187 Karlsruhe, Germany. J. Ni and E. Sandvol, Department of Physics, New Mexico State University, Las Cruces, NM 88003, USA. J. Nabelek, College of Oceanography, Oregon State University, Corvallis, OR 97331, USA. L. Chen, H. Tan, W. Wei, China University of Geosciences, Beijing, China. A. G. Jones, Geological Survey of Canada, 1 Observatory Crescent, Ottawa, Ontario, Canada. J. Booker and M. Unsworth, Geophysics Program, University of Washington, Seattle, WA 98195, USA. W. S. F. Kidd and M. Edwards, Department of Geosciences, SUNY-Albany, Albany, NY 12222, USA〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8939851" target="_blank"〉PubMed〈/a〉

Description: Global Seismic Network data were used to image upper-mantle seismic discontinuities. Stacks of phases that precede the PP phase, thought to be underside reflections from the upper-mantle discontinuities at depths of 410 and 660 kilometers, show that the reflection from 410 kilometers is present, but the reflection from 660 kilometers is not observed. A continuous Lame's constant lambda and seismic parameter at the 660-kilometer discontinuity explain the missing underside P reflections and lead to a P-wave velocity jump of only 2 percent, whereas the S-wave velocity and density remain unchanged with respect to previous global models. The model deemphasizes the role of Lame's constant lambda with regard to the shear modulus and constrains the mineralogical composition across the discontinuity.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Estabrook -- Kind -- New York, N.Y. -- Science. 1996 Nov 15;274(5290):1179-82.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉GeoForschungsZentrum Potsdam, Telegrafenberg, D- 14473 Potsdam, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8895464" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kind, Rainer -- Yuan, Xiaohui -- New York, N.Y. -- Science. 2010 Sep 17;329(5998):1479-80. doi: 10.1126/science.1191620.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Deutsches GeoForschungsZentrum, Telegrafenberg, 14473 Potsdam, Germany. kind@gfz-potsdam.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20847259" target="_blank"〉PubMed〈/a〉

Description: We used more than 40 000 S-receiver functions recorded by the USArray project to study the structure of the upper mantle between the Moho and the 410 km discontinuity from the Phanerozoic western United States to the cratonic central US. We obtained clear observations of downward velocity reductions in the uppermost mantle which are commonly interpreted as the lithosphere-asthenosphere boundary (LAB) in the western US and as the mid-lithospheric discontinuity (MLD) in the cratonic US. We observe the western LAB reaching partly to the mid-continental rift system underneath the cratonic crust. The MLD is surprisingly plunging steeply towards the west from the Rocky Mountains Front to about 200 km depth near the Sevier Thrust Belt. There is a significant break in the lithosphere at the Sevier Thrust Belt. We also observe a velocity reduction about 30 km above the 410 km discontinuity in the same region where in the western US the LAB is observed, but not in the cratonic US.

Description: We analyze S-receiver functions to investigate the variations of lithospheric thickness below the entire region of Turkey and surroundings. The teleseismic data used here have been compiled combining all permanent seismic stations which are open to public access. We obtained almost 12 000 S-receiver function traces characterizing the seismic discontinuities between the Moho and the discontinuity at 410 km depth. Common-conversion-points stacks yield well-constrained images of the Moho and of the lithosphere–asthenosphere boundary (LAB). Results from previous studies suggesting shallow LAB depths between 80 and 100 km are confirmed in the entire region outside the subduction zones. We did not observe changes of LAB depths across the North and East Anatolian Faults. To the east of Cyprus, we see indications of the Arabian LAB. The African plate is observed down to about 150 km depth subducting to the north and east between the Aegean and Cyprus with a tear at Cyprus. We also observed the discontinuity at 410 km depth and a negative discontinuity above the 410, which might indicate a zone of partial melt above this discontinuity.

Description: We used more than 40 000 S-receiver functions recorded by the USArray project to study the structure of the upper mantle between the Moho and the 410 km discontinuity from the Phanerozoic western United States to the cratonic central US. In the western United States we observed the lithosphere–asthenosphere boundary (LAB), and in the cratonic United States we observed both the mid-lithospheric discontinuity (MLD) and the LAB of the craton. In the northern and southern United States the western LAB almost reaches the mid-continental rift system. In between these two regions the cratonic MLD is surprisingly plunging towards the west from the Rocky Mountain Front to about 200 km depth near the Sevier thrust belt. We interpret these complex structures of the seismic discontinuities in the mantle lithosphere as an indication of interfingering of the colliding Farallon and Laurentia plates. Unfiltered S-receiver function data reveal that the LAB and MLD are not single discontinuities but consist of many small-scale laminated discontinuities, which only appear as single discontinuities after longer period filtering. We also observe the Lehmann discontinuity below the LAB and a velocity reduction about 30 km above the 410 km discontinuity.

Description: New combined P receiver functions and seismicity data obtained from the EGELADOS network employing 65 seismological stations within the Aegean constrained new information on the geometry of the Hellenic subduction zone. The dense network and large data set enabled us to estimate the Moho depth of the continental Aegean plate across the whole area. Presence of a negative contrast at the Moho boundary indicating the serpentinized mantle wedge above the subducting African plate was seen along the entire forearc. Furthermore, low seismicity was observed within the serpentinized mantle wedge. We found a relatively thick continental crust (30–43 km) with a maximum thickness of about 48 km beneath the Peloponnese Peninsula, whereas a thinner crust of about 27–30 km was observed beneath western Turkey. The crust of the overriding plate is thinning beneath the southern and central Aegean and reaches 23–27 km. Unusual low Vp / Vs ratios were estimated beneath the central Aegean, which most likely represent indications on the pronounced felsic character of the extended continental Aegean crust. Moreover, P receiver functions imaged the subducted African Moho as a strong converted phase down to a depth of about 100 km. However, the converted Moho phase appears to be weak for the deeper parts of the African plate suggesting nearly complete phase transitions of crustal material into denser phases. We show the subducting African crust along eight profiles covering the whole southern and central Aegean. Seismicity of the western Hellenic subduction zone was taken from the relocated EHB-ISC catalogue, whereas for the eastern Hellenic subduction zone, we used the catalogues of manually picked hypocentre locations of temporary networks within the Aegean. Accurate hypocentre locations reveal a significant change in the dip angle of the Wadati–Benioff zone (WBZ) from west (~ 25°) to the eastern part (~ 35°) of the Hellenic subduction zone. Furthermore, a zone of high deformation can be characterized by a vertical offset of about 40 km of the WBZ beneath the eastern Cretan Sea. This deformation zone may separate a shallower N-ward dipping slab in the west from a steeper NW-ward dipping slab in the east. In contrast to hypocentre locations, we found very weak evidence for the presence of the slab at larger depths in the P receiver functions, which may result from the strong appearance of the Moho multiples as well as eclogitization of the oceanic crust. The presence of the top of a strong low-velocity zone at about 60 km depth in the central Aegean may be related to the asthenosphere below the Aegean continental lithosphere and above the subducting slab. Thus, the Aegean mantle lithosphere seems to be 30–40 km thick, which means that its thickness increased again since the removal of the mantle lithosphere about 15 to 35 Ma ago.