(St-40) Receiver Function (RF) Estimation Using Short Period Seismological Data Shantanu Pandey Department of Earth Sciences, Kurukshetra University, Kurukshetra-136119 Abstract The advent of the receiver function (RF) technique has dramatically altered the traditional concept of the composition and structure of the crust and its evolution through geologic times. The combined power of P-to-S converted signals (Ps phase) from any interface with adequate velocity contrast, and their multiply reflected and converted waves between the surface and the interface, known as multiples recorded in the RFs are used to simultaneously determine the depth to the interface and constrain the average V P /V S (related to Poisson’s ratio s) of the intervening region. This case study is an attempt to explore the power and limitations of short period (data) RFs and strategise effective ways and means to make better use of the short-period data. It is demonstrated that short-period data after restitution and application of appropriate low pass filters can indeed become useful for H- V P /V S studies. The efficacy of this simple approach is tested and demonstrated on data from the Japanese island arc setting. After restitution (de-convolving instrument effect from the data), the range of band-pass period best suited for the Japanese data varied from a minimum of 1.5 to 3s up to a maximum of 15 to 20s. The resultant filtered RFs have come out with sharper Ps and multiple arrivals. The choice of optimal filters after restitution is found region sensitive. In conclusion, we find that: a) restituted short period RFs can be used to estimate the crustal thickness (H) and Poisson ratio (s) due to improved quality in observation of the multiple phases (Pps, Pss), b) the restituted short-period data is ‘broadband’ enough to pick signals related to the first P- and S- multiples even in a complex setting such as the Japanese islands, and c) appropriate choice of the low pass filters and the band-pass range need to be tailored after careful study of the data. Introduction Knowledge about the structure of the earth’s interior used to narrow down the competing hypotheses for continental evolution has mainly emerged from seismological studies as it reveal presence of a stratified earth, based on changes in its physical and chemical properties with depth manifested as seismic velocity discontinuities. These acts as building blocks to trace the evolutionary path of the earth, since they carry in their bowels the imprints of both past and present convective regimes of the mantle, which are governed by the motion of tectonics plates, resulting in the observed diverse surface geologic expressions. Teleseismic P waveforms recorded at a three- component seismic section contains immense information about the earthquake sources, the earth’s structure in the vicinity of both source and receiver, and mantle propagation effects. If the source and mantle propagation effects are eliminated then we are able to obtained the local crustal and upper mantle structure underneath the station. Source equalized receiver function analysis is such a technique to explore crustal and upper mantle structure at the receiver site. A seismic signal that essentially contains the effects of local structure beneath a station devoid of effects due to source complexities and path effects is termed as Receiver function (Ammon, 1997). The teleseismic record is the output of convolution of seismic source, underlying structure response and the instrument effect besides some noise. Owing to the large velocity contrast at any interface (e.g. crust-mantle boundary), the incoming incident teleseismic P energy partly gets converted into P-to-S waves that transmit across the boundary besides the direct arrivals and reflections. These transmitted P and P-to-S conversions (Ps) in turn can get multiply reflected between the free surface and the interface (converter) resulting in multiples of varied nature. From these Ps conversions and Pps, Pss multiples, we get a first-order information about the crustal structure beneath a station (Zhu and Kanamori 2000). Most of the available RF images focus on use of broadband data from various networks to map the underlying crust-mantle structure. The main apprehension to use short-period data for H-V P /V s determination is based on the apparent belief that multiple (Pps, Ps s ) may be poorly registered by short period (1 Hz) sensors. This case study is intended to study the power and limitations of short period data RF’s and strategies effective ways and means to make better use of the large amount of short-period data accrued in the past and remains unutilized.