In the early hours of 11 January 1962 little town of Makarska on the eastern shores of the Adriatic Sea was shaken by a magnitude ML = 6.1 earthquake. A couple of days prior, on 7 January, there was a strong foreshock (ML = 5.9) that foreshadowed the event to come. These earthquakes caused extensive damage to Makarska and surrounding villages. Also, the mainshock possibly induced a small water column disturbance recorded at the city of Split harbour tide-gauge as a 3 cm wave 40 min after the mainshock’s occurrence time. Modelling of this disturbance estimated that the maximum vertical motion of the sea-bottom was about 15 cm. Apart from this, little is known about this earthquake. Epicentre location and faulting mechanism have been estimated although with large uncertainty due to a low number of seismic stations operating at the time.
One of the aims of the CRONOS project is to look for active seismic structures in this region and to map it – and what immediately stands out is the 1962 Makarska earthquake and many unknowns connected to this event. Therefore, we decided to further investigate this event by locating the source fault. The best estimate for the surface expression of this fault was below the Adriatic Sea, in the channel between the islands of Brač and Hvar and the mainland. To map any possible surface deformation of the active fault responsible for the Makarska earthquake, we decided to do the shallow seismic sounding of the topmost seabed sedimentary layers around the estimated source location of the 1962 earthquake.
In the two-day cruise, on 30 and 31 January 2024, we aimed to locate a possible activated fault and the source of the 1962 tsunami through the surface expression of the earthquake either in the bathymetry or in the topmost sedimentary layers under the seafloor. Measurement were performed by the Hydrographic Institute of the Republic of Croatia from Split and they were accompanied by geologist Igor Vlahović (RGNF) and seismologists Josip Stipčević (PMF) form the Component 1 of the CRONOS project. In those two days, ten intersecting profiles were recorded and interesting results were obtained, but their detailed analysis and interpretation will follow.
Prepared by Josip Stipčević and Iva Dasović
