code: def _compute_mean(self, C, mag, rrup):
          
          mean = np.zeros_like(rrup)
  
          mean += C['c1'] + C['c2'] * mag + C['c3'] * (8.5 - mag) ** 2
  
          idx = rrup > 70.
          mean[idx] += C['c7'] * (np.log(rrup[idx]) - np.log(70.))
  
          idx = rrup > 130.
          mean[idx] += C['c8'] * (np.log(rrup[idx]) - np.log(130.))
  
          R = np.sqrt(
              rrup ** 2 + (C['c5'] * np.exp(C['c6'] * mag)) ** 2
          )
          mean += C['c4'] * np.log(R) + (C['c9'] + C['c10'] * mag) * rrup
  
          return mean
docs: Compute mean value (Equation 30 in USGS report)