P-wave receiver functions are fundamental tools in seismology. They help us understand the structure of the Earth beneath seismic stations by analyzing how P-waves interact with subsurface boundaries. This technique isolates the local response from the complex seismic signals we record.
The deconvolution process is the mathematical heart of receiver function analysis. We take the radial component seismogram and deconvolve it with the vertical component. This effectively removes the earthquake source signature and the effects of wave propagation through the upper Earth, leaving us with a clean signal that represents only the local structure beneath the station.
The receiver function reveals various seismic phases generated at subsurface discontinuities. When a P-wave hits a boundary like the Moho, part of its energy converts to an S-wave, creating a Ps phase. We also see multiple reflections like PpPs and PsPs phases. These converted phases and multiples provide detailed information about the depth and properties of major boundaries like the Moho and mantle transition zone.
A typical receiver function shows distinct peaks corresponding to major Earth discontinuities. The Moho appears as a strong positive peak at 2 to 8 seconds, depending on crustal thickness. The 410 kilometer discontinuity shows up around 40 seconds, and the 660 kilometer boundary appears near 65 seconds. The timing of these peaks directly relates to the depth of the discontinuities, while their amplitude indicates the strength of the velocity contrast.
P-wave receiver functions have revolutionized our understanding of Earth's internal structure. They allow us to map crustal thickness variations across continents, study the complex structure of subduction zones, and investigate the mantle transition zone. The technique is particularly valuable because it provides high vertical resolution using data from a single seismic station, making it a cost-effective method for studying Earth's deep structure. From monitoring volcanic systems to understanding continental evolution, receiver functions continue to be an essential tool in modern seismology.