Observations of guided waves from the Pamir seismic zone provide additional evidence for the existence of subducted continental lower crust

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985530%3A_____%2F19%3A00507752" target="_blank" >RIV/67985530:_____/19:00507752 - isvavai.cz</a>

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/abs/pii/S0040195119301180?via%3Dihub" target="_blank" >https://www.sciencedirect.com/science/article/abs/pii/S0040195119301180?via%3Dihub</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.tecto.2019.04.007" target="_blank" >10.1016/j.tecto.2019.04.007</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Observations of guided waves from the Pamir seismic zone provide additional evidence for the existence of subducted continental lower crust

Popis výsledku v původním jazyce

As part of the TIPAGE (Tien shan - PAmir GEodynamic program) project, passive seismological observations were made along an approximately N-S profile crossing the Pamir seismic zone for about one year. From these observations guided waves were recognized. These guided waves occur as a single, continuous, secondary, compressional (P) wave phase behind the first P-wave arrivals. An equivalent phase in the shear (S) wavefield is hardly recognizable. Modelling of the phase shows that an approximately 10 km thick low velocity zone (LVZ) between the Moho and about 160 km depth reproduces the guided waves as a single, continuous phase much better than a 15-20 km thick LVZ. Modelling of the arrival times of the guided waves reveals that a model with a P-wave velocity of 6.3 km/s above about 100 km depth, and a velocity of 7.6 km/s between this depth and the deep cluster of earthquakes at about 150 km depth provides the best fit to the observed travel-time data. One plausible way to explain the low velocity of 6.3 km/s is to invoke the presence of melts in the LVZ. Then, taking a velocity of 6.9 km/s for the lower crust being subducted, about 10-13% melt is required to obtain a velocity of about 6.3 km/s in the LVZ between the Moho and about 100 km depth. This would be in keeping with the estimated burial depths from xenoliths of Gondwana terrane affinity brought to the surface in the southeastern Pamir around 11 million yr. ago. The present-day LVZ is interpreted to comprise continental lower crust. Although guided waves are known to exist associated with subducted oceanic crust or fault zones, this is the first time to the knowledge of the authors that guided waves have been observed resulting from a LVZ associated with subducted continental lower crust.

Název v anglickém jazyce

Observations of guided waves from the Pamir seismic zone provide additional evidence for the existence of subducted continental lower crust

Popis výsledku anglicky

As part of the TIPAGE (Tien shan - PAmir GEodynamic program) project, passive seismological observations were made along an approximately N-S profile crossing the Pamir seismic zone for about one year. From these observations guided waves were recognized. These guided waves occur as a single, continuous, secondary, compressional (P) wave phase behind the first P-wave arrivals. An equivalent phase in the shear (S) wavefield is hardly recognizable. Modelling of the phase shows that an approximately 10 km thick low velocity zone (LVZ) between the Moho and about 160 km depth reproduces the guided waves as a single, continuous phase much better than a 15-20 km thick LVZ. Modelling of the arrival times of the guided waves reveals that a model with a P-wave velocity of 6.3 km/s above about 100 km depth, and a velocity of 7.6 km/s between this depth and the deep cluster of earthquakes at about 150 km depth provides the best fit to the observed travel-time data. One plausible way to explain the low velocity of 6.3 km/s is to invoke the presence of melts in the LVZ. Then, taking a velocity of 6.9 km/s for the lower crust being subducted, about 10-13% melt is required to obtain a velocity of about 6.3 km/s in the LVZ between the Moho and about 100 km depth. This would be in keeping with the estimated burial depths from xenoliths of Gondwana terrane affinity brought to the surface in the southeastern Pamir around 11 million yr. ago. The present-day LVZ is interpreted to comprise continental lower crust. Although guided waves are known to exist associated with subducted oceanic crust or fault zones, this is the first time to the knowledge of the authors that guided waves have been observed resulting from a LVZ associated with subducted continental lower crust.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10507 - Volcanology

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2019

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Tectonophysics

ISSN

0040-1951

e-ISSN

—

Svazek periodika

762

Číslo periodika v rámci svazku

July

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

16

Strana od-do

1-16

Kód UT WoS článku

000470940400001

EID výsledku v databázi Scopus

2-s2.0-85064693613