Detailed velocity ratio mapping during the aftershock sequence as a tool to monitor the fluid activity within the fault plane

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985530%3A_____%2F16%3A00464264" target="_blank" >RIV/67985530:_____/16:00464264 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216208:11310/16:10331721

Výsledek na webu

<a href="http://dx.doi.org/10.1016/j.epsl.2016.08.017" target="_blank" >http://dx.doi.org/10.1016/j.epsl.2016.08.017</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.epsl.2016.08.017" target="_blank" >10.1016/j.epsl.2016.08.017</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Detailed velocity ratio mapping during the aftershock sequence as a tool to monitor the fluid activity within the fault plane

Popis výsledku v původním jazyce

The rheological properties of Earth materials are expressed by their seismic velocities and V-P/V-S ratio, which is easily obtained by the Wadati method. Its double-difference version based on cross-correlated waveforms enables focusing on very local structures and allows tracking, monitoring and analysing the fluid activity along faults. We applied the method to three 2014 mainshock-aftershock sequences in the West Bohemia/Vogtland (Czech Republic) earthquake swarm area and found pronounced V-P/V-S variations in time and space for different clusters of events located on a steeply dipping fault zone at depths ranging from 7 to 11 km. Each cluster reflects the spatial distribution of earthquakes along the fault plane but also the temporal evolution of the activity. Low values of V-P/V-S ratio down to 1.59 +/- 0.02 were identified in the deeper part of the fault zone whereas higher values up to 1.73 +/- 0.01 were estimated for clusters located on a shallower segment of the fault. Temporally the low V-P/V-S values are associated with the early aftershocks, while the higher V-P/V-S ratios are related only to later aftershocks. We interpret this behaviour as a result of saturation of the focal zone by compressible fluids: in the beginning the mainshock and early aftershocks driven by over-pressured fluids increased the porosity due to opening the fluid pathways. This process was associated with a decrease of the velocity ratio. In later stages the pressure and porosity decreased and the velocity ratio recovered to levels of 1.73, typical for a Poissonian medium and Earth's crust.

Název v anglickém jazyce

Detailed velocity ratio mapping during the aftershock sequence as a tool to monitor the fluid activity within the fault plane

Popis výsledku anglicky

The rheological properties of Earth materials are expressed by their seismic velocities and V-P/V-S ratio, which is easily obtained by the Wadati method. Its double-difference version based on cross-correlated waveforms enables focusing on very local structures and allows tracking, monitoring and analysing the fluid activity along faults. We applied the method to three 2014 mainshock-aftershock sequences in the West Bohemia/Vogtland (Czech Republic) earthquake swarm area and found pronounced V-P/V-S variations in time and space for different clusters of events located on a steeply dipping fault zone at depths ranging from 7 to 11 km. Each cluster reflects the spatial distribution of earthquakes along the fault plane but also the temporal evolution of the activity. Low values of V-P/V-S ratio down to 1.59 +/- 0.02 were identified in the deeper part of the fault zone whereas higher values up to 1.73 +/- 0.01 were estimated for clusters located on a shallower segment of the fault. Temporally the low V-P/V-S values are associated with the early aftershocks, while the higher V-P/V-S ratios are related only to later aftershocks. We interpret this behaviour as a result of saturation of the focal zone by compressible fluids: in the beginning the mainshock and early aftershocks driven by over-pressured fluids increased the porosity due to opening the fluid pathways. This process was associated with a decrease of the velocity ratio. In later stages the pressure and porosity decreased and the velocity ratio recovered to levels of 1.73, typical for a Poissonian medium and Earth's crust.

Druh

J_x - Nezařazeno - Článek v odborném periodiku (Jimp, Jsc a Jost)

CEP obor

DC - Seismologie, vulkanologie a struktura Země

OECD FORD obor

—

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2016

Kód důvěrnosti údajů

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

Název periodika

Earth and Planetary Science Letters

ISSN

0012-821X

e-ISSN

—

Svazek periodika

453

Číslo periodika v rámci svazku

November

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

8

Strana od-do

215-222

Kód UT WoS článku

000383932300021

EID výsledku v databázi Scopus

2-s2.0-84991255923