A vector triangle solution near the Solomons Trench-Woodlark Rift triple point gives underthrusting of the Solomons Plate beneath the northern Solomon Trench in a northeasterly direction at about 11 centimeters per year.
2.
Multiple editors including myself have tried walking David through the derivation, but he adopts some rather strange limitations to the derivation ( his vector triangle argument ) and uses very nonstandard terminology ( like what he calls radial acceleration ).