The expression of fear, sympathy and solidarity in relation to geo-distance, social ties and personal visits. (a-c) are scatterplots of the fear correlation (with square root transformation for normality) with Boston against geographic proximity (inverse distance in kilometers), number of replies, and number of personal visit, respectively. (d-f) are scatterplots of #prayforboston volume (total number of tweets containing the hashtag) against the three factors. (g-i) are scatterplots of #bostonstrong against the three factors. In all plots, non-US and US cities are colored in red and blue, respectively. The correlation coefficients are reported on top of the scatterplots, where (a-c) are Pearson correlation coefficients between the variables x and , and (d-i) are Spearman’s rank correlation coefficients between the variables x and y. All coefficients are significant with . Among the 35 non-US cities, #prayforboston appeared in 25 cities, while #bostonstrong only appeared in 3 cities (Toronto, Montreal, and Melbourne). Cities with zero #prayforboston or #bostonstrong hashtags are not shown.