According to Billboard.com:
The Chili Peppers' No. 1 Modern Rock debut is only the second in the chart's history, following R.E.M.'s "What's the Frequency, Kenneth?" in September 1994. It's also the Chili Peppers' ninth No. 1, a new record for the format. The quartet had previously been tied with Green Day and U2 for all-time Modern Rock chart toppers.