Constraints and Uncertainties in Recognizing Active Faults for Database Compilation: Insights from Greece

In this contribution, we analyze and discuss the recently published Active Faults Greece (AFG) database highlighting how poorly constrained and inaccurate practices could impact the overall results. The analysis of the 3814 fault traces and the 892 individual faults proposed in the AFG emphasizes several critical aspects (such as lacking major geomorphological evidence, fault length exaggeration, improper reporting of blind faults, mapping of fault traces without precision, tracing and characterization of faults without field control, proposal of fault traces differing from well-mapped historical earthquake ruptures, omission and misjudgment of the literature, etc.). All these issues effectively invalidate the AFG, discredit the results presented to the public, and introduce a strong bias in any possible estimate of seismic hazard. Furthermore, we outline the criticalities caused by misleading, uncertain, or disputed data transmitted to administrators, professionals, and the public in general, who do not have the capacity or sufficient knowledge and expertise for carefully verifying the applicability of the product for seismic hazard assessment analyses. For secure fault data definition, the remote sensing/geomorphological approach at the base of the AFG could certainly be useful, but definitely not sufficient. Indeed, for the compilation of internationally recognized databases of seismogenic sources and active fault traces, the systematic and critical analysis of historical and/or instrumental seismicity, palaeoseismological, morphotectonic, geodetic, remote sensing, shallow geophysical techniques, and structural investigations would be required.