During the past few decades, it has become clear that the Earth's components - atmosphere, ocean and solid Earth - interact in complex ways on various time scales. Seismograms reveal such interactions, mainly on days without large earthquakes. One example is the continuous background oscillations that were first reported in 1998, whose cause is actually still unknown. The goal of this proposed study is to understand the cause and mechanism of these ubiquitous seismic oscillations and to learn the implications for mechanical couplings between the ocean and the solid earth. Thus, it represents a scientific pursuit for understanding a novel enigmatic phenomenon. While the detection of this phenomenon was achieved by solid earth scientists, the phenomenon is relevant to the state of the atmosphere and oceans and thus could be of interest to a broader range of earth scientists. This is a global phenomenon for the entire Earth system.
As with any other scientific pursuit of new knowledge, it can have some future benefits. For example, in solid earth science, it may be critical for detection of slow earthquakes in the future, within the frequency band 2-15 mHz, because the continuous oscillations are the principal source of noise in this frequency band. There is some hint that previous seismological slow-earthquake studies have been hampered by these oscillations. Understanding the nature of this phenomenon will give us insight into how to reduce noise and enhance other signals in the same frequency band.
This study takes advantage of seismic and satellite ocean data whose complementary use have not been examined before. It may be a good example of what can be done with accumulation of large amount of data, happening in geosciences as well as in broader scientific disciplines. Truly surprising discoveries will be made beyond the walls of small disciplines that have been categorized in modern sciences. In order to advance our understanding of the Earth as a dynamically connected system, there is no question that conscious efforts toward connecting data in different disciplines will be required. In addition, this project will educate a graduate student working for a Ph.D. degree.
