code: def _compute_magnitude_terms(self, rup, coeffs):
          
  
          adj_mag = rup.mag - self.CONSTS['ref_mag']
          return coeffs['c1'] + coeffs['c2']*adj_mag + coeffs['c3']*adj_mag**2
docs: First three terms of equation (8) on p. 203:
  
          ``c1 + c2*(M - 6) + c3*(M - 6)**2``