 |
| Titel |
Project TIPAGE wide-angle seismic data reveals the crustal structure along a profile across the Pamir and southern Tien Shan. |
| VerfasserIn |
James Mechie, Xiaohui Yuan, Bernd Schurr, Felix Schneider, Christian Sippl, Vlad Minaev, Mustafo Gadoev, Ilhomjon Oimahmadov, Ulan Abdybachaev, Bolot Moldobekov |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047581
|
|
|
|
|
|
| Zusammenfassung |
| Utilizing seismic refraction / wide-angle reflection data from six approximately
in-line earthquakes, two-dimensional P and S velocity models and a Poisson’s ratio
model of the crust and uppermost mantle have been derived along the 400 km long
main profile of the TIPAGE (TIen shan – PAmir GEodynamic program) project.
These models show that the crustal thickness varies from about 65.5 km close to the
southern end of the profile beneath the South Pamir through about 73.5 km under
Lake Karakul in the North Pamir, to about 59.5 km, 60 km S of the northern end of
the profile in the southern Tien Shan. Average crustal P velocities are low with
respect to the global average, varying from 6.22-6.32 km s-1. The average crustal
S velocity is 3.60-3.65 km s-1 along the whole profile and thus average crustal
Poisson’s ratio (Ïă) varies from 0.245 in the south to 0.255 in the north. The main
layer of the upper crust extending from about 2 km below the Earth’s surface to 26
km depth below sea level (b.s.l.) has P velocities which increase from 5.93 km
s-1 in the south to 6.07 km s-1 in the north. This is in contrast to the S velocities
which decrease from 3.50 km s-1 in the south to 3.44 km s-1 in the north with a
corresponding increase in Ïă from 0.23 to 0.26. The low value of 0.23 for Ïă at the
southern end of the profile is similar to that within the corresponding layer beneath
central Tibet and is indicative of felsic rocks rich in quartz in the α state. The lower
crust below 31 km b.s.l. has P velocities ranging from 6.2-6.3 km s-1 at the top to
7.2 km s-1 at the base. Ïă for this layer is low at about 0.25 which is similar to
values found in the northeast Tibetan plateau. Within the uppermost mantle, the
average P velocity is about 8.10 km s-1 and Ïă is about 0.26. Assuming an isotropic
situation, then a relatively cool (650-750Ë C) uppermost mantle beneath the profile
is indicated. This would in turn indicate an intact mantle lid beneath the profile. |
|
|
|
|
|
|