When load_usgs returns an empty DataFrame it has a RangeIndex, causing
resample("1D") to throw TypeError. Guard with an isinstance check and
fall back to a zero series so the rest of the pipeline continues.
Also aligns expected usgs-dir path with what script 06 wrote.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Scripts 01-08 implement the complete cosmic-ray/earthquake correlation
analysis from data ingestion through out-of-sample validation and
combined timeseries sinusoid fitting.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>