They were NOT convicted of failing to predict a quake. Here's the nutshell version of what happened, to the best of my recollection:
A medieval stone city sits in an area that has a long history of earthquake swarms. Since the 1300's the residents of the city have had a standard way of responding to them...when the first quake hits, they evacuate some of the more dangerous parts of town, camp outside of their homes, etc. This is perfectly normal to them, and has a long local history. Sometimes this go on for months, and sometimes just days. Instead of living in their dangerous homes, they get our of them until the "danger passes".
In 2009 two small quakes hit, and many of the people in the town quickly began preparations to evacuate or began moving outside of their homes. The government official, along with several seismologists, went to a town hall meeting and on TV to tell the people in the town that there was no need to evacuate or worry, that earthquakes couldn't be predicted, and that they were perfectly safe in their homes. The towns traditional response to the swarms was to get to safety, but the local government and these seismologists told them to stay in their homes. Documents showed that the seismologists were actually aware of the towns history of earthquake swarms, but the overriding concern at a meeting between them and the local government was to pacify the town and "keep things normal".
When the quake struck 7 days later, over 300 people were killed as the old stone buildings collapsed on them. If the townspeople had evacuated or moved outside, a substantial percentage of them may have lived.