Fig 3. Linear relationship between time of arrival T_a and effective distance D_eff.

(a and b) Linear relationship between time of arrival T_a and geographical distance D_geo at 1^st epidemic wave from Kanagawa (a) and at 2^nd epidemic wave from Tokyo (b). (c and d) Linear relationship between time of arrival T_a and effective distance D_eff at 1^st epidemic wave from Kanagawa (c) and at 2^nd epidemic wave from Tokyo (d). HKD: Hokkaido, CBA: Chiba, TKY: Tokyo, KGW: Kanagawa, ACH: Aichi, OSK: Osaka, FKK: Fukuoka, OKW: Okinawa, STM: Saitama. The size of the bubble represents the sum of the number of cases in each prefecture.