La Spezia earthquake, June 23 2016

On 23 June at 16:37 (14:37 UTC), an earthquake of magnitude Mw = 3.7 occurred a few kilometers from La Spezia, in the town of Santo Stefano di Magra. The earthquake has been strongly felt all along the northern Tuscan coast up to Livorno. Safety checks on public buildings and on the railway lines have been disposed by the mayors of the municipalities concerned.

The quake was recorded by the seismometer SEP, producing the beautiful track in the figure below. The arrival of the P and S waves is well defined. The difference in arrival times between the S and P waves is 9 s and indicates that the epicenter is located about 65-70 km from our seismic station.

We applied a high pass filter with 1 Hz frequency since the SEP is a suitable instrument to record long-term signals typical of earthquakes that occur at great distance. In the case of local earthquakes, such as that of La Spezia, the waves that reach the instrument have instead a higher frequency. The filtered trace is shown in red in the figure below.