SUBSURFACE STRUCTURE MODELING BASED ON RECEIVER FUNTION ANALYSIS AS AN INTERPRE- TATION OF TELESEISMIC EARTHQUAKE

Abstract

The Nusa Tenggara to Timor region lies within a complex tectonic zone resulting from the interaction between the Indo-Australian and Eurasian Plates, which drives significant seismic activity and crustal structural variations. This study aims to char- acterize the crustal structure across the Nusa Tenggara-Timor region through teleseismic receiver function analysis and 𝐻 − 𝜅 stacking methods. Broadband seismic station data were analyzed to extract radial receiver functions capturing P- to-S wave conversions and their multiples. Three key findings emerge: (1) System- atic crustal thickness variations ranging from 34.22 ± 1.2 km in collision zones (Ti- mor) to 41.15 ± 1.5 km in active subduction sectors (Flores), with maximum thick- ness (>39 km) observed near the plate interface; (2) Elevated 𝑉𝑝/𝑉𝑠 ratios (1.85- 1.95) correlate with volcanic arcs, suggesting mafic underplating or melt retention, while lower ratios (1.70-1.75) reflect felsic continental fragments; (3) Scatter plot analysis of crustal thickness, 𝑉𝑝/𝑉𝑠 ratio, and surface elevation reveals no signifi- cant linear correlations between these parameters. These observations indicate that crustal growth in this transitional subduction system is primarily controlled by sub- duction-related magmatism and tectonic inheritance rather than uniform thickening processes.