Banca de DEFESA: JOSÉ RICHARLES ALMEIDA GOMES

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : JOSÉ RICHARLES ALMEIDA GOMES
DATE: 18/12/2020
TIME: 10:30
LOCAL: https://www.youtube.com/channel/UCTGgqsUdEvXATvUqtAwyxPg
TITLE:

Monitoring velocity changes in the Saint Peter Saint Paul Archipelago using ambient noise interferometry

KEY WORDS:

Ambient Noise Interferometry; Auto-correlation, Saint Peter and Saint Paul, Monitoring, mid-Atlantic Ridge

PAGES: 66
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

The Saint Paul Transform System (SPTS) is located in th MId-Atlantic Ridge (MAR), Equatorial Atlantic and is formed by a multi-fault complex system, where many faults are interacting and small-to-moderate events are routinely located in the area using global seismic networks. This seismicity is challenging to charecterize since no permanent seismic stations near this area is available. As a result, the effect of the seismic events on the rock mass and the inter-play between seismicity, faulting and fluid in the MAR is poorly constrained. In this dissertation, we quantify the seismic velocity pertubations due to small-to-moderate magnitude earthquakes in the Saint Peter Saint Paul Archipelago (SPSPA) using one seismographic station installed in the region. We calculate noise auto-correlation functions using the data recorded by this station. The auto- correlograms were obtained by two different approaches: classical auto-correlation geometrically normalized (ACGN) and phase autocorrelation (PAC). We found that both approaches give very similar results and we are able to estimate velocity changes due to small earthquakes (between 3.0 and 4.7 ML). The changes in the medium were investigated through the joint analysis of decorrelation curves and velocity changes obtained by Moving Window Cross Spectral (MWCS) method. Our analysys show that the velocity changes are possibly associated with a hydromechanical coupling in which the observed velocity increase is driven by static stress changes and fluid-rock interaction is responsible for the observed velocit drop. This behavious is qualitatively explained by the multi-fault complex system nature of the SPTS, where fluid-rock interaction plays an important role in the observed velocity variation

BANKING MEMBERS:
Presidente - 1451214 - ADERSON FARIAS DO NASCIMENTO
Interno - 1863578 - JORDI JULIA CASAS
Externo à Instituição - MARCELO PERES ROCHA - UnB