Sleep tracking is one of the best features of the Jawbone Up fitness tracker, but it could serve a purpose beyond helping you feel less groggy in the morning. Jawbone's data science team has collated the sleep information from last night in northern California — which was hit by its biggest earthquake in 25 years — and used it to show what percentage of Up wearers in each city were woken up at 3:20AM PT. Napa was among the worst affected areas, whereas Santa Cruz barely registered a tremor, according to the sleep data.