Morse code is an on/off pulse pattern, where the "on" pulses are either short or long.
At another layer, when "on" what is sent is a stable tone of a fixed frequency. When "off" there is nothing sent, just quiet.
I think the seismic event was like a single "on" pulse (no short and long components, just an ongoing ringing tone) with a tone that can be described as each cycle lasting 17 seconds in duration (very low frequency tone.)
The absence of any on/off pattern, or variation in the tone during the event, doesn't sound like morse code. But things like this are good to look for in the seismic signature.