Passage Summary: Every time a big earthquake happens, small shakes come first; since we just had small shakes, a big one must be coming.

Conclusion: A major earthquake will occur in the region soon.

Reasoning: Every major earthquake in the past was preceded by minor tremors, and minor tremors have just occurred.

Analysis: This argument commits a classic formal logic error: confusing a necessary condition for a sufficient one. The author establishes that tremors are a necessary precursor to a big quake, but then incorrectly assumes they are sufficient to guarantee one. When looking for a match, find an argument that says 'If A happens, B must have happened before it; B just happened, so A is about to happen.' You are looking for that specific 'backwards' logic where the presence of a requirement is treated as a guarantee of the outcome.