Ammianus Marcellinus

Ammianus Marcellinus (c. 330 - c. 391-400 CE), also known as Ammian, was
an officer and soldier in the Roman armies of
Constantius II (r. 337- 361 CE)
and
Julian the Apostate (r. 361-363 CE where he served in Gaul and the East
(
wikipedia). Ammianus was born in Syria
and likely was fluent in Greek, Latin, and his native language (
wikipedia).
After retiring from the military, he moved to Rome where he wrote wrote Res Gestae - a history of Rome from 96-378 CE
(
wikipedia).
Ammianus was a Pagan but modern scholarship describes him as
tolerant of Christianity
(
wikipedia). In Res Gestae,
Ammianus wrote a brief account of events surrounding the Cyril Quakes.
Although he does not mention the earthquakes, he does mention the effort to rebuild the Temple and fire bursting forth from the foundations.