Critical Evaluation of Strong Ground Motions in Izmir and Implications for Future Earthquake Simulation Results
Abstract. Izmir, a major city in western Turkey, is located in a highly seismic region, subject to frequent earthquakes due to its proximity to active fault systems. This paper critically evaluates the strong ground motions recorded in Izmir, with a focus on understanding the implications for urban infrastructure and future seismic hazard mitigation. Historically available data is collected and compared with the available ground motion prediction equations (GMPE). Later, the most appropriate prediction equation is selected and used to determine the target response spectrum. 2020 Sisam earthquake is a well-documented seismic event and the data from the stations are then used to further calibrate the 1D site response model. Lastly, possible future events are generated and results are compared with the current Turkish Earthquake Code (TEC). Amplification factors prescribed by code for İzmir Bay have been surpassed by projected future events, highlighting the necessity for reassessment. Therefore, region-specific seismic zoning should be established when standard code practices fall short in accounting for significant site effects. Concrete recommendations about local site modification factors and evaluations on this topic have been provided within the article.
General Evaluation
This manuscript addresses a highly relevant and practical problem: evaluating strong ground motions in Izmir and implications for future earthquake simulations using GMPEs, site response analyses (SRA), and comparison with Turkish Earthquake Code (TEC) design spectra. The study includes an extensive dataset, thoughtful site-specific calibration, and a compelling case for re-evaluating seismic design spectra for alluvial zones in Izmir. The work is timely and important, particularly in the context of recent seismic events like the 2020 Samos Earthquake.
Although the manuscript requires several clarifications and presentation improvements, these revisions do not affect the core methodology or conclusions. Therefore, I recommend acceptance after minor revision.
General Comments:
These are not major scientific flaws, but addressing them will improve the clarity, quality, and impact of the paper:
A short paragraph clearly stating how this study builds upon or extends those provious works (e.g., broader dataset, new scenario, comparison with TEC, etc.) would be helpful.
Some plots (e.g., Figures 7–13) suffer from low resolution, small font sizes, and unclear legends. It is recommended to:
Minor grammatical errors and awkward phrasing (e.g., “data riched event”) should be corrected throughout the manuscript. A careful proofreading or light professional editing is encouraged.
While the GMPE selection and SRA analyses are rigorous, a brief paragraph discussing epistemic uncertainties (e.g., in soil properties, GMPE selection) would strengthen the credibility of the conclusions.
Since the RADIUS project dates back to 1997, it would be useful to mention whether newer seismic source models or hazard assessments (e.g., AFAD, SHARE) have been compared or considered.
Detailed comments by section
Section 1.1 (Scope and Aim):
Section 1.2 (Geological and Geotechnical Settings of İzmir Bay):
“Loosely consolidated sediments can exacerbate ground shaking” → “Loose alluvial soils with low stiffness can significantly amplify seismic waves, particularly in the 0.5–2 s period range.”
Section 2: GMPE Dataset and Model Comparison
Section 3: Site Response Validation
Section 4: Target Spectrum and Future Scenario Analysis
Section 5: Summary and Conclusions
Final Recommendation: Minor Revision
The manuscript presents a valuable, technically sound, and well-structured contribution to seismic hazard evaluation and future earthquake simulation in İzmir. With minor improvements in figure clarity, language quality, and justification of novelty, the paper will be ready for publication.