There are 144 blocks found on average each day so for one day the standard deviation error is 100 / sqrt(144) or about 8%. Two deviations are 16%
Keep in mind that on bitcoin wisdom, even the shortest period trend line (the grey one) is based on 504 blocks. It seems highly unlikely the current spike is just a statistical anomaly (or normality if you prefer
).It could be previously turned off hardware being turned on again, but more likely IMO is that a next gen asic has arrived. Bitfury was supposed to bring their 28nm 0.2W/GH online by the end of last year. AFAIK, that didnt happen, maybe it did now. Asicminer and SP with very similar specs shouldnt be very far behind.