Thesis: Image-Domain Ambient Recording Tomography
Active-source seismic recording and imaging is a robust and highly used method for imaging 3D Earth structure. However, under certain circumstances active-source methods may be unusable in the real world. Utilising ambient seismic energy that naturally propagates in the Earth is an alternative method that has begun to garner interest in the scientific community. Herein, I propose to extend the method of 3D ambient seismic data processing and imaging to adjoint-state inversion methods to utilise the ambient energy in the Earth, not only to create images but also to estimate and verify subsurface models with unknown energy sources. To do this I will investigate methods for extracting weak body-wave signals present in ambient seismic recordings and using them to create subsurface images. I will further explore the sensitivity of these images to subsurface velocity model errors, expressed as image misfocussing, and then extend existing adjoint-state methods to inverting these misfocussing errors for velocity model updates.
Why my research is important
As seismic recording technology has improved, there are many places where recording ambient seismic energy in the Earth has been done without the need to do so, and this data is generally stored away and not used in exploration. This data has information about the subsurface embedded in it that can be used to improve the imaging methods used in exploration or even replace the current methods under the proper circumstances. Because there are many sources of ambient data and it occurs at all places and locations in the Earth, it is very important to develop methods to use and model this data for exploration.