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Chapter 7:Hazard Analysis—Earthquakes <br /> Historically, the largest earthquakes in Hawaii have occurred at shallower depths, beneath <br /> the flanks of Kilauea, Mauna Loa and Hualalai Volcanoes. The flanks of these volcanoes <br /> adjust to the intrusions of magma into their adjacent rift zones by storing compressive <br /> stresses and occasionally releasing it in crustal earthquakes. The active fault surfaces for <br /> these large earthquakes is associated with a near-horizontal basal decollement separating the <br /> ancient oceanic crust from the emplaced volcanic pile, lying approximately 10 km beneath <br /> the Earth's surface. (A decollement is a tectonic surface that acts as a plane of detachment <br /> between two masses.) Examples of such crustal or decollement earthquakes occurred in <br /> 1975, the M7.2 (or greater) Kalapana earthquake beneath Kilauea's south flank, and in 1868, <br /> the largest earthquake in recorded Hawaiian history beneath the Ka`u district on Mauna <br /> Loa's southeast flank, estimated as a M7.9 earthquake. (Figure 7-2 by Klein, et al,2001). <br /> l HAWAII HISTORICAL EARTHQUAKES <br /> CRUSTAL <br /> 10/15/2006 • EARTHQUAKES <br /> M6.0 Z=18 r <br /> ' • M 7.0-7.9 <br /> 1 /1885 <br /> PaClflC �� I�t. �Y�"",�. 8M6.1 <br /> 18ti1 y M 6.5-6.9 <br /> OCBaIl MRA ,•4 ' /' <br /> 11/18/41- t • M 6.0-6.4 <br /> .M61 MA ,. <br /> 10/15/2006 n� r M62 Z MANTLE EARTHQUAKES <br /> M6.7 Z=39 , Ms2 =3s <br /> r< <br /> (Z>15) <br /> A <br /> HUALALAI ' �,1 ,®Hilo <br /> :one <br /> MAUNALOA <br /> NE P <br /> �•�" ;` : ', KILAUEAaStPkklooe <br /> r <br /> Q • � -Old <br /> 8155 <br /> 3/28/1868 • . M s.a <br /> M 6.1,7U D . 5/31116771 /29175 <br /> M 6.3; M 7.2 <br /> 4/22151 <br /> M 6.2 <br /> of 4/2/1868 <br /> 0 30 km <br /> M7.9 Pacific <br /> Ocean <br /> Figure 7-2. Hawaii Historical Earthquakes and Inferred Rupture Zones of the Larger Events <br /> 7-2 Hawaii County Multi-Hazard Mitigation Plan <br />