Iranian Journal of Geophysics

Iranian Journal of Geophysics

Determining apparent source time function (ASTF) of seismic events through empirical green function analysis (a case study of Khoy 2023 earthquake)

Document Type : Research Article

Authors
Khalil Bakhtiari Asl 1
Vladimir Plicka 2
Khosro Moghtased- Azar 3
1 M.Sc., Department of Geomatics Engineering, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
2 Ph.D., Department of Geophysics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
3 Associate Professor, Department of Geomatics Engineering, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
10.30499/ijg.2025.480141.1638
Abstract
The study examines the Apparent Source Time Function (ASTF) for four seismic stations (MRD, SDS1, URUN, and MAHB) in relation to the Khoy earthquake. By employing the method developed by (Plicka,  et al. 2022), we meticulously calculate the ASTFs to investigate the temporal distribution of seismic energy release during the earthquake. Our analysis reveals significant variations in ASTF duration across the different stations. Specifically, the MRD station exhibits a notably short ASTF duration of 5 seconds, whereas the URUN station shows a considerably longer ASTF duration of 18 seconds. The SDS1 and MAHB stations fall in between, with ASTF durations of 15 seconds and 12 seconds, respectively. These observed variations in ASTF durations likely indicate differences in fault properties and rupture dynamics at each station. The shorter ASTF at MRD may suggest a more abrupt energy release, while the longer ASTF at SDS1 could imply a more prolonged rupture process. The intermediate durations at URUN and MAHB further highlight the complexity and variability of seismic energy release mechanisms. Our findings contribute valuable insights into seismic hazard assessment and fault characterization in the Khoy region. By applying the ASTF calculation method to this specific case study, we demonstrate its utility in enhancing our understanding of earthquake dynamics. This innovative application underscores the importance of ASTF analysis in seismic studies and its potential to inform more accurate seismic hazard models. Furthermore, our research opens up new avenues for future investigations. We suggest that subsequent studies should focus on a broader range of seismic events and stations to validate and refine the ASTF method. Additionally, exploring the relationship between ASTF characteristics and other seismic parameters, such as fault slip and rupture velocity, could provide deeper insights into the underlying mechanisms of earthquake generation. In conclusion, this study not only advances our knowledge of the Khoy earthquake but also highlights the broader applicability of ASTF analysis in seismology. Our work underscores the need for continued research in this area to improve seismic hazard assessments and enhance our understanding of earthquake processes. By integrating ASTF analysis with other geophysical methods, we can develop a more comprehensive picture of seismic activity, ultimately contributing to better preparedness and mitigation strategies in earthquake-prone regions. This holistic approach will be crucial for advancing the field of seismology and ensuring the safety and resilience of communities affected by seismic events. The insights gained from this study can also be applied to other regions with similar seismic profiles, thereby broadening the impact and relevance of our findings.
 
Keywords
Apparent source time function, earthquake source parameter estimation, EGF

Subjects

Courboulex, F., J. Virieux, A. Deschamps, D. Gibert and A. J. G. J. I. Zollo (1996). "Source investigation of a small event using empirical Green's functions and simulated annealing."  125(3): 768-780.
Hough, S., J. Lees and F. J. B. o. t. S. S. o. A. Monastero (1999). "Attenuation and source properties at the Coso Geothermal Area, California."  89(6): 1606-1619.
Hough, S. J. J. o. G. R. S. E. (1997). "Empirical Green's function analysis: Taking the next step."  102(B3): 5369-5384.
Hutchings, L., G. J. E. R. Viegas and A.-N. F. i. Seismology (2012). "Application of empirical Green’s functions in earthquake source, wave propagation and strong ground motion studies." 87-140.
Hutchings, L. J. B. o. t. S. S. o. A. (1991). "“Prediction” of strong ground motion for the 1989 Loma Prieta earthquake using empirical Green's functions."  81(5): 1813-1837.
Irikura, K. (1984). Prediction of strong ground motions using observed seismograms from small events. Proc. 8th World Conf. on Earthq. Eng.
López‐Comino, J. Á., F. d. L. Mancilla, J. Morales and D. J. G. R. L. Stich (2012). "Rupture directivity of the 2011, Mw 5.2 Lorca earthquake (Spain)."  39(3).
Mueller, C. S. J. G. R. L. (1985). "Source pulse enhancement by deconvolution of an empirical Green's function."  12(1): 33-36.
Plicka, V., F. Gallovič, J. Zahradník, A. Serpetsidaki, E. Sokos, N. Vavlas and A. J. T. Kiratzi (2022). "The 2020 Samos Mw7 earthquake: Source model depicting complexity and rupture directivity."  843: 229591.
Salmanian, M., A. Rastbood and M. M. J. J. o. A. E. S. Hossainali (2025). "Evaluating interseismic deformation patterns in the North Tabriz Fault (Iran) using enhanced fitting of velocity field and analysis of surface deformation."  277: 106376.
Salmanian, M., A. Rastbood and M. M. J. J. o. G. S. Hossainali (2024). "Estimating the slip rate in the North Tabriz Fault using focal mechanism data and GPS velocity field."  14(1): 20220167.
Stein, S. and M. Wysession (2009). An introduction to seismology, earthquakes, and earth structure, John Wiley & Sons.
Iranian Journal of Geophysics
Volume 19, Issue 6
January and February 2026
Pages 125-138