The wikipedia page gives references for the terms of the predictability debate.

"Despite the confident announcement four decades ago that seismology was "on the verge" of making reliable predictions,[247] there may yet be an underestimation of the difficulties. As early as 1978 it was reported that earthquake rupture might be complicated by "heterogeneous distribution of mechanical properties along the fault",[248] and in 1986 that geometrical irregularities in the fault surface "appear to exert major controls on the starting and stopping of ruptures".[249] Another study attributed significant differences in fault behavior to the maturity of the fault.[250] These kinds of complexities are not reflected in current prediction methods.[251]

Seismology may even yet lack an adequate grasp of its most central concept, elastic rebound theory. A simulation that explored assumptions regarding the distribution of slip found results "not in agreement with the classical view of the elastic rebound theory". (This was attributed to details of fault heterogeneity not accounted for in the theory.[252])

Earthquake prediction may be intrinsically impossible. It has been argued that the Earth is in a state of self-organized criticality "where any small earthquake has some probability of cascading into a large event".[253] It has also been argued on decision-theoretic grounds that "prediction of major earthquakes is, in any practical sense, impossible."[254]

That earthquake prediction might be intrinsically impossible has been strongly disputed[255] But the best disproof of impossibility – effective earthquake prediction – has yet to be demonstrated.[256]"

I had to dig out working links to the refs.

[253] Geller, Robert J.; Jackson, David D.; Kagan, Yan Y.; Mulargia, Francesco (14 March 1997), "Earthquakes Cannot Be Predicted", Science, 275 (5306): 1616, doi:10.1126/science.275.5306.1616.

[254] Matthews, Robert A. J. (December 1997), "Decision-theoretic limits on earthquake prediction", Geophysical Journal International, 131 (3): 526–529, Bibcode:1997GeoJI.131..526M, doi:10.1111/j.1365-246X.1997.tb06596.x.](

[255] Sykes, Lynn R.; Shaw, Bruce E.; Scholz, Christopher H. (1999), "Rethinking Earthquake Prediction" Pure and Applied Geophysics, 155 (2–4): 207–232, Bibcode:1999PApGe.155..207S, doi:10.1007/s000240050263.

[255] Evison, Frank (October 1999), "On the existence of earthquake precursors", Annali di Geofisica, 42 (5): 763–770.