Over the past week, multiple sources have reported that Japan's Internet services are still working, despite the damage suffered by some underwater communication cables during the Sendai earthquake and tsunami. To capture the extent of the impact from the perspective of our users, we looked at the number of online users before and after the event.
To see how BitTorrent usage was affected relative to typical activity patterns, we compared data from the week of the earthquake with data from the same time in the previous week. In the graph on the right, the yellow line represents the number of peers found between Wednesday March 2nd and Sunday March 6th, while the blue line represents the number of peers online between Wednesday March 9th and Sunday the 13th -- the week of the earthquake. For the most part, the number of BitTorrent peers that we see in Japan is similar between the two weeks.
The exception can be seen in the 24-hour period immediately following the earthquake, which occurred at 2:46PM local time on Friday, March 11th. As the graph shows, the number of BitTorrent peers found online differed by as much as 25% in this period compared to the previous week at the same time. Surprisingly, we still see a large number of peers online and activity returns to normal on Saturday morning.
We are carrying on additional analysis to better understand how these events affected not only Internet connectivity and performance for people in Japan, but also for users in other countries, as a result of the damaged communication cables and rerouting of network paths.