The regional moment tensor of the 5 May 2014 Chiang Rai earthquake (Mw = 6.5), Northern Thailand, with its aftershocks and its implication to the stress and the instability of the Phayao Fault Zone

•30 FMS of 5 May 2014 event and aftershocks are derived from RMT inversion.•The main event has Mw 6.5 recorded as the largest earthquake in Thailand.•Maximum compression (σ1) axis in Northern Thailand is in N18E direction.•A high shear stress Mae Lao segment was likely to initiate the slip.•The 11 September 1994 event was likely a strike – slip, not normal motion.