Paleoseismology

Paleoseismology is the scientific study of prehistoric earthquakes. It seeks to reconstruct the history of earthquakes on faults by examining geological and geomorphic evidence preserved in rocks, sediments, and landforms. By extending the earthquake record beyond the instrumental era, paleoseismology helps characterize fault behavior over timescales of thousands to tens of thousands of years.

The primary method involves trenching across active faults to expose and log stratigraphic layers that record sudden ground disruption. Seismically induced features, such as ground ruptures, liquefaction structures, and seismites in sedimentary sequences, provide physical markers of past events. Dating techniques, including radiocarbon dating, luminescence dating, and dendrochronology, establish approximate event ages. Correlating contemporaneous deposits along a fault and using geomorphic landforms allows reconstruction of event sequences and estimates of slip per event and recurrence intervals.

Results from paleoseismology feed into seismic hazard assessments by providing long-term statistics on fault behavior, maximum magnitudes, and earthquake frequency. They also help identify fault segments with potential for earthquakes and inform land-use planning and building codes in seismically active regions. Tsunami paleoseismology, based on offshore cores and coastal stratigraphy, extends hazard assessment to tsunami potential as well.

Limitations include preservation bias, incomplete records, dating uncertainties, and lateral variability along a fault. Interpretations often require multiple trenches, cross-cutting evidence, and integration with other geological data to build a robust earthquake history.