1 Geologic and geomorphic controls on rockfall hazard: how well do past rockfalls predict 2 future distributions? 3 4 Josh Borella 1,2, Mark Quigley 3,2, Zoe Krauss 4,1, Krystina Lincoln 5,1, Januka Attanayake 3, 5 Laura Stamp 5,1, Henry Lanman 6,1, Stephanie Levine 7,1, Sam Hampton 1,2, Darren Gravley 1,2 6 7 1 Frontiers Abroad, 3 Harbour View Terrace, Christchurch, 8082, New Zealand 8 2 Department of Geological Sciences, University of Canterbury, Christchurch, 8041, New Zealand 9 3 School of Earth Sciences, The University of Melbourne, Victoria, 3010, Australia 10 4 Department of Geology, Colorado College, Colorado Springs, CO, 80903, USA 11 5 Department of Geosciences, Williams College, Williamstown, MA, 01267, USA 12 6 Department of Geology, Whitman College, Walla Walla, WA, 99362, USA 13 7 Department of Geology, Carleton College, Northfield, MN, 55057, USA 14 15 Correspondence: Josh Borella (
[email protected]) 16 17 KEYWORDS: Rockfall hazard, boulder spatial distributions, frequency-volume distributions, 18 Canterbury Earthquake Sequence, prehistoric rockfall boulders, deforestation, rockfall 19 source characteristics, rockfall physical properties, rockfall numerical modelling, 20 Christchurch 21 22 Abstract 23 24 To evaluate the geospatial hazard relationships between recent (contemporary) rockfalls and 25 their prehistoric predecessors, we compare the locations, physical characteristics, and 26 lithologies of rockfall boulders deposited during the 2010-2011 Canterbury earthquake 27 sequence (CES) (n=185) with those deposited prior to the CES (n=1093). Population ratios of 28 pre-CES to CES boulders at two study sites vary spatially from ~5:1 to 8.5:1. This is interpreted 29 to reflect (i) variations in CES rockfall flux due to intra- and inter-event spatial differences in 30 ground motions (e.g.