Yield estimation of small explosions at local distances represents a challenge for the nuclear explosion monitoring community. We have examined the feasibility of using short‐period surface‐wave magnitudes, called , to estimate explosion yields at local distances (<100 km). We have modified the Russell (2006)Ms formula, which was derived for periods of 8–25 s for distances beyond 50 km, for application at local distances and 1 s period. We have studied short‐period surface‐wave attenuation in diverse lithologies in order to incorporate an attenuation term in the magnitude scale, which is suitable for . We have also incorporated multiple excitation corrections for based on the near‐source seismic velocities, which greatly affect the source‐region amplitudes for . It is important to note that in the formula the excitation is estimated from the measured group velocity. We have also derived a new Butterworth filter cutout definition for filtering near 1 s period at distances between 2 and 100 km. We used the new formula to estimate for 39 small (37≤Y≤12,270 kg TNT equivalent) and shallow (<120 m) explosions detonated in North America in lithologies ranging from alluvium to granite. Regressions of the magnitudes with yield result in the equation for chemical explosions with Y<12,270 kg. An F factor with 95% confidence was determined to be 2.25, giving lower and upper bounds on the yield estimates of Y/2.25 and Y×2.25, respectively. We applied the relationship (assuming factor of 2 equivalence between chemical and nuclear) to nuclear explosions detonated at the Degelen and Shagan, Kazakhstan, test sites. The estimated yields based on magnitudes were often within 20% of the true yield and had smaller F factor than the estimated yields for United States chemical explosions.
Online Material: Tables of event information and estimates.