In BSSA, the abstract is below. Note that the most obvious precursor was the foreshocks, whose existence is well-documented, but also documented to be not very effective.

However, for me the bottom line is that the result was never clearly proven, and in the 30 years since, with far greater instrumentation and much more scientific methods, the result has not been reproducible. Some of the results from China of that era, such as the dramatically understated death tolls of the big earthquakes, also suggest an element of wishful thinking to science in that time and place.

Predicting the 1975 Haicheng Earthquake

Kelin Wang1, Qi-Fu Chen2, Shihong Sun3 and Andong Wang4

The publicized four-stage (long-term, middle-term, short-term, and imminent) prediction of the M 7.3 1975 Haicheng, China, earthquake once generated worldwide fascination. Yet the prediction process has remained mysterious because of lack of reports on real-time documentation and details of how warnings were issued. In the present work, study of declassified Chinese documents and interviews of key witnesses have allowed us to reconstruct this important history. Our findings indicate that there were two official middle-term predictions but no official short- term prediction. On the day of the earthquake, a county government issued a specific evacuation order, and actual actions taken by provincial scientists and government officials also effectively constituted an imminent prediction. These efforts saved thousands of lives, but the local construction style and time of the earthquake also contributed to minimizing fatalities. Evacuation was extremely uneven across the disaster region, and critical decisions were often made at very local levels. The most important precursor was a foreshock sequence, but other anomalies such as geodetic deformation, changes in groundwater level, color, and chemistry, and peculiar animal behavior also played a role.