The identification of true and quasi 'anti-repeating' earthquakes, neighboring events characterized by anti-correlated waveforms, indicates that nearly opposite fault slips can occur sequentially within the same or adjacent structures. Although documented in only a few regions to date, their occurrence across diverse tectonic, volcanic, and induced settings suggests that anti-repeaters may be a more prevalent seismic phenomenon than currently recognized. A systematic global analysis of large to moderate earthquakes by scanning 48 years of the Global CMT catalog for neighboring pairs with nearly opposite moment tensors reveals a surprising abundance of such events. We identified 3,431 earthquake pairs organized into more than 300 spatial clusters. Their presence across diverse seismogenic environments, including subduction zones, ridges, active volcanoes, and the upper mantle, is reflected in the high variability of their depths, magnitudes, and focal mechanisms. These findings establish a global phenomenon, but further studies are required to determine whether individual cases represent specific rupture processes, such as volcanic inflation-deflation, reversed ridge ruptures or the activation of intersecting fault networks and to distinguishing between true and quasi-anti-repeating mechanisms, i.e. those affecting the same fault segments or neighboring ones.
