While in cruise; CRJ200 Captain reports amber 'STAB TRIM' and 'MACH TRIM' CAS messages. After complying with QRH procedures crew diverts to nearest suitable airport.

Narrative

While in cruise with the autopilot on; we received an amber Stab Trim and Mach Trim CAS message. As Pilot Flying; I assumed the radio and First Officer was directed to the QRH for the Stab Trim. After following the QRH and directions for Maintenance Control via ACARS; we elected to declare an emergency with Center. Since by this time ZZZ was the closest suitable airport with a long enough runway (per the QRH we would be performing a flaps 20 degree landing). Crash Fire Rescue was alerted and placed on standby; but did not roll from their quarters. Upon completion of the QRH; the aircraft was hand flown due to the out-of-trim condition. First Officer and I rotated these duties in order to allow each pilot to remain fresh due to the large amounts of back pressure needed to maintain altitude. During this time the Flight Attendant was notified of the situation and was given 20 minutes to prepare the cabin. I also made a cabin PA announcement to the passengers explaining the situation. The Brace command/positions were not used. The flight; approach; and landing were uneventful other than the fact that it was at flaps 20 degrees and a little faster than normal. After landing; a PA announcement was made to the passengers explaining that all was normal and that we would be taxiing to the gate.