engleski

Tsunami excitation and propagation in the central Adriatic archipelago - the case of Makarska earthquake

The Makarska earthquakes of 1962 represent the most important seismic sequence in Croatia in the last 50 years. The mainshock (ML = 6.1) occurred in the area between the mainland and the islands of Hvar and Brac on 11 January at 05:05. Fault plane solutions for the three largest events indicate reverse faulting on a steeply dipping, WNW-ESE striking fault, which also agrees with the position of the relocated hypocentres. The dip-slip component of the motion on the fault was large enough to cause vertical sea-bottom displacement of about 15 cm, which in turn could have generated a small tsunami. The horizontal dimensions of the source area are estimated by empirical formulas to be of the order of 10 km. As the bottom depth in the area ranges between 10 and 100 m, a linear shallow-water model could be used to simulate the tsunami. The model equations have been solved using a finite-difference numerical scheme (resolution 500 m/10 s). The modelled tsunami reveals some interesting features: short waves are detained in the source area, probably due to scattering caused by the irregularities of the coastline; long waves propagate outwards, through the Brac, Hvar and Neretva Channels; and the tsunami is somewhat amplified near the coasts, primarily as a result of refraction. The simulated tsunami is compared to the corresponding tide-gauge record from Split. The observed arrival time and amplitudes agree well with those of the synthetic tsunami, if it is assumed that initial disturbance was due to the subsidence of the foot wall of the seismo-genetic fault - in agreement with tectonic motions in the area.

tsunami; central Adriatic archipelago; the case of Makarska earthquake

nije evidentirano