Most earthquake location programs provide the user with some estimate of the error in the calculated hypocentral solution. Because the criteria used in estimating these errors differ, a cross-reference guide of error estimates is provided herein for some of the more widely used programs (HYPOELLIPSE, FASTHYPO, HYPO71, and HYPOINVERSE).
In all the programs considered, an individual confidence interval is given for the depth error. For the epicentral error, HYPO71 and HYPOINVERSE provide only individual confidence estimates, while the other programs provide epicentral joint confidence regions. The programs differ in the type of statistic used: a x2 statistic (HYPOELLIPSE), or no explicitly assumed statistic (HYPO71, HYPOINVERSE, FASTHYPO). There are also differences in confidence levels: 83% (HYPOELLIPSE epicentral region), 94% (HYPOELLIPSE depth interval), 39% (FASTHYPO epicentral region assuming a x2, value of 1.0), and 68% (FASTHYPO, HYPO71, and HYPOINVERSE depth intervals assuming a x2 value of 1.0). In almost all cases, confidence intervals and regions can be rescaled to a common reference.