Question: when did san francisco last have an earthquake
[{'answer': 'The 1989 Loma Prieta earthquake', 'provenance': [{'wikipedia_id': '261671', 'title': '1989 Loma Prieta earthquake', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 31, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '261671', 'title': '1989 Loma Prieta earthquake', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 738, 'bleu_score': 0.85947691930636, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8902676200384047735}, 'section': 'Section::::Abstract.'}]}]