Special Seminar - Lucia Gualtieri
|March 21st, 2017
Lamont-Doherty Earth Observatory
Studying environmental processes through seismic signals
The last decade has witnessed a renaissance in the breadth of applications of seismology, which extended into non-traditional areas with the aim of studying environmental processes. Non-traditional seismology is a rapidly growing, relatively new, and inherently multidisciplinary research field. In this talk, I will present new findings on two applications of seismology for studying environmental processes: 1) seismic ambient noise and 2) seismic signals generated by mass-wasting events.
Seismic ambient noise is the continuous vibration of the Earth recorded worldwide, in response to the interaction between the atmosphere, the ocean, and the solid Earth. The strongest signal is called secondary microseismic noise and it is generated by the non-linear interaction between ocean gravity waves. Seismic noise source location and amplitude can be assessed by using a realistic ocean wave model and described as a pressure distribution at the ocean surface. Employing these sources, I modelled the amplitude of noise spectra in a variety of environments, accounting for the resonance effect that the ocean produces on the amplitude of ambient noise sources. Possible applications of this modelling approach include the estimate of the contribution of the different ocean basins on seismic noise amplitude in various seasons and the location of seismic sources associated with strong atmospheric events.
The study of mass-wasting events through seismic signals is another recent application of seismology. A mass-wasting event, like a rockfall or a landslide, involves forces that load and unload the Earth as the mass moves. These forces generate seismic waves. Seismic data analysis and numerical modelling provide a way to infer the dynamics and the main characteristics of such events, particularly in the absence of direct observations. Two events, different in nature, are discussed in this talk: a) a large rockfall that occurred along the west side of the Hudson River Palisades (NY), on May 13, 2012 and b) a massive landslide that occurred near Icy Bay (Alaska), on October 17, 2015. By using the seismic data recorded at nearby stations and simulating the propagation of seismic waves in realistic Earth models, I reconstruct time-varying point forces associated with these events. From these force histories, it is possible to deduce the mass, the runout trajectory, and the main characteristics associated with the center of mass of rockfalls and landslides.
Room 54-209, Reception to Follow
All are welcome to attend