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Analysing Alpine Fault Earthquakes Through Ambient Seismic Noise

Description: 

The Alpine Fault is the primary seismic hazard in Southern New Zealand, rupturing in M7-8 earthquakes roughly every ∼300 years, with the last event in 1717 AD. Yet, empirical data on ground shaking does not exist due to the absence of recorded Alpine Fault earthquakes. Numerical models that simulate shaking from possible Alpine Fault earthquakes provide key information to assist in hazard mitigation but current state-of-the-art models are too computationally expensive, limiting their ability to compute a comprehensive range of potential earthquake source scenarios.

Our approach sidesteps these limitations by estimating ground shaking using ambient seismic noise for modelling wave propagation. Ambient noise, often seeming random and incoherent in seismograms, can reveal coherent energy travelling between two seismic stations through cross-correlation, deconvolution, and coherency analyses. We apply the Virtual Earthquake method, which uses ambient seismic noise to compute empirical Green’s functions between station pairs. These empirical Green’s functions are modified from a surface point-force source to a double-couple source at depth. This method allows us to investigate ground shaking from many rupture scenarios comprising a broad suite of possible Alpine Fault earthquakes.

We use ambient noise records of both permanent networks and the novel SALSA (Southern Alps Long Skinny Array), a network of broadband seismometers strategically deployed every ∼10 km along the Alpine Fault, which facilitates a comprehensive investigation of diverse rupture scenarios. This study showcases the potential of using ambient seismic noise to unravel seismic behaviour, offering a valuable tool for predicting and mitigating seismic hazards.

Session: 3D Wavefield Simulations: From Seismic Imaging to Ground Motion Modelling [Poster Session]

Type: Poster

Date: 5/2/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Ilma del Carmen

Student Presenter: Yes

Invited Presentation: 

Authors