Testing the new INQUA intensity scale in Greek earthquakes

Testing the new INQUA seismic intensity scale is an important challenge in the fields of macroseismology and earthquake geology. In order to calibrate and compare the new scale with conventional scales, intensities were tested for two Greek earthquakes: Elia, NW Peloponnese, 16 October 1988 (Ms=5.9) and Athens, central Greece, 7 September 1999 (Ms=5.9). The selected earthquakes were strong, and their macroseismic effects included not only damage to buildings and other structures but also ground failures such as local landslides, rockfalls, ground fissures and liquefaction. The macroseismic fields of the selected earthquakes were studied and intensities in Modified-Mercalli (MM) scale were assessed. An inventory of macroseismic effects was created. Intensities in the MM and INQUA scales were assessed for several observation points as regards the two earthquakes. INQUA scale intensities assessed for the Elia 1988 earthquake are as high as those resulting from the MM scale. This is because the intensity assessment in INQUA scale is based on ground damages, and many ground cracks, rock falls and liquefaction in sediment, were extensively associated with the Elia earthquake. The case of the Athens 1999 earthquake is significantly different from that of the Elia earthquake. MM intensities as high as IX were assessed due to the extensive structural damage. However, INQUA intensities fail to approach adequately the MM intensities because there were only a few ground failures, with only sporadic rockfalls and/or landslides. Because of this, INQUA intensities underestimate the overall impact of the Athens earthquake.