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What Core Samples from New Zealand’s Largest Fault Revealed Adapted from Information by The University of Texas at Austin A paper describing the latest discovery to emerge from two scientific drilling expeditions in New Zealand led by scientists at The University of Texas at Austin and colleagues at institutions in New Zealand, indicates the area’s largest fault is a mix- ture of rocks of all shapes, sizes, compositions, and origins. This odd assortment of rocks from half a mile beneath the seafloor, indicates a mixture of weak and strong points in the planet’s crust which scientists believe may influence the occur- rence of earthquakes. It could even help explain why the fault generates slow-motion earthquakes known as “slow slip events” in addition to destructive, tsunami-generating tremors. “One thing that really surprised us was the sheer diversity of rock types,” said Laura Wallace, a research scientist at the University of Texas Institute for Geophysics (UTIG) and cochief scientist on the expedition which retrieved rock samples from the fault. “These rocks that are being mashed up together, all behave very differently in terms of their earthquake generating potential.” Subduction zones are located where one tectonic plate goes beneath another. These zones are where the largest and most damag- ing earthquakes occur. Scientists have long contemplated why quakes are more powerful or more frequent in certain subduction zones, and whether there is a connection with the slow slip events, which can take weeks or months to unfold. Although they are not felt by people on the surface, the energy they release is comparable to powerful earth- quakes. The team drilled into the remains of a buried, ancient sea mountain where they found pieces of volcanic rock, hard, chalky, carbonate rocks, clay-like mudrocks, and layers of sediments eroded from the mountain’s surface. Kelin Wang, an expert in earthquake physics and slow slip events at the Geological Survey of Canada, said the paper was effectively a breakthrough in understanding how the same fault can generate different types of earthquakes. “In addition to helping us understand the geology of slow slip events, this paper also helps explain how the same fault can exhibit complex slip behav- ior, including tsunami-generating earthquakes,” said Wang, who was not part of the study. 257 Caroline Street Punxsutawney, PA 15767 800-927-0560 • 814-427-2555 Fax: 814-427-5164 SERVING THE WATER WELL INDUSTRY Serving the Drilling Industry 16 AUGUST 2020 WorldWide Drilling Resource ® Photo of the core samples courtesy of the International Ocean Discovery Program’s JOIDES Resolution Science Operator. ENV