Lloyd S. Cluff

Representative Styles of Deformation along the Chelungpu Fault from the 1999 Chi-Chi (Taiwan) Earthquake: Geomorphic Characteristics and Responses of Man-Made Structures

The Chi-Chi earthquake provides dramatic evidence of the damaging effects of surface ground deformation to buildings, lifelines, and other facilities. Much of the building damage is associated with surface faulting and folding along the Chelungpu thrust fault. Our detailed surveying at representative sites along the fault shows that the rupture commonly is a relatively simple 1- to 4-m-high scarp with minor hanging-wall deformation and localized (but severe) uplift, folding, and graben formation along the scarp crest. For individual scarps, the width of deformation is about 10 to 20 times the net vertical displacement. Distributed secondary faulting and folding on the hanging wall occurred as much as 350 m from the primary fault. Near the northern end of the rupture, growth of a pre-existing 1-km-wide late Quaternary anticline produced severe ground rupture along multiple thrusts and backthrusts but only minor tilting between fault strands.nnThe pattern of building damage coincides with the pattern of geologic deformation, with severe damage along large fault scarps and lesser but still significant damage attributable to distributed secondary surface deformation on the hanging wall. Rupture-related building damage on the footwall occurred next to the prerupture fault trace, where the hanging wall bulldozed onto the footwall. The width of this damage zone is related to the local horizontal shortening along the fault and generally is less than 10 m. Building zonation along reverse faults should account for this pattern of surface deformation. In addition, buildings with massive foundations locally influenced the style and location of near-surface deformation, producing variations in fault strike or accentuated secondary deformation on the hanging wall.nnManuscript received 15 January 2001.

Surface Rupture on the Denali Fault Interpreted from Tree Damage during the 1912 Delta River Mw 7.2–7.4 Earthquake: Implications for the 2002 Denali Fault Earthquake Slip Distribution

During the 3 November 2002 Denali fault earthquake, surface rupture propagated through a small, old-growth forest in the Delta River valley and damaged many trees growing on the fault. Damage was principally the result of fault offset of tree roots and tilting of trees. Some trees were split by surface faults that intersected the base of their trunks or large taproots. A few trees appear to have been damaged by strong shaking. Many of the older trees damaged in 2002 were deformed and scarred. Some of these scarred trees exhibit past damage indicative of surface faulting and have abrupt changes in their annual ring patterns that coincide with the past damage. Annual ring counts from several of these older scarred trees indicate the damage was caused by surface rupture on the Denali fault in 1912. The only earthquake of sufficient magnitude that fits the requirements for timing and general location as recorded by the damaged trees is a widely felt M s 7.2–7.4 earthquake on 6 July 1912 informally referred to as the 1912 Delta River earthquake. Seismologic data and intensity distribution for the 1912 Delta River earthquake indicate that its epicenter was within 60–90 km of the Delta River and that rupture probably propagated toward the west. Inferred fault length, displacement, and rupture direction suggest the 1912 rupture was probably largely coincident with the western, lower slip section of the 2002 rupture.

Trans-Alaska Pipeline System Performance in the 2002 Denali Fault, Alaska, Earthquake

The Trans-Alaska Pipeline System is one of the most significant engineering achievements of the 20th century and the first major pipeline system for which considerable attention was focused on the identification and quantification of potential seismic hazards and the implementation of design and operational features to address those hazards. One of these special design features included the concept for an above-ground supporting system for the pipeline crossing of the Denali fault. The 2002 M7.9 Denali fault earthquake represents the first successful test of a structure specifically designed for fault displacement. The earthquake also demonstrated the benefits of the multi-tiered earthquake preparedness and response strategy in place at the time of the earthquake.

Active Faults and Nuclear Power Plants

The destruction of the Fukushima Daiichi Nuclear Power Plant (NPP) following the March 2011 Tohoku earthquake and tsunami brought into sharp focus the susceptibility of NPPs to natural hazards. This is not a new issue—seismic hazard has affected the development of plants in the United States, and volcanic hazard was among the reasons for not commissioning the Bataan NPP in the Philippines [Connor et al., 2009].

Geoengineering and Seismological Aspects of the Niigata-Ken Chuetsu-Oki Earthquake of 16 July 2007

The M6.6 Niigata-Ken Chuetsu-Oki earthquake of 16 July 2007 occurred off the west coast of Japan with a focal depth of 10 km, immediately west of Kashiwazaki City and Kariwa Village in southern Niigata Prefecture. Peak horizontal ground accelerations of 0.68 g were measured in Kashiwazaki City, as well as at the reactor floor level of the world’s largest nuclear reactor, located on the coast at Kariwa Village. Liquefaction of historic and modern river deposits, aeolian dune sand, and manmade fill was widespread in the coastal region nearest the epicenter and caused ground deformations that damaged bridges, embankments, roadways, buildings, ports, railways and utilities. Landslides along the coast of southern Niigata Prefecture and in mountainous regions inland of Kashiwazaki were also widespread affecting transportation infrastructure. Liquefaction and a landslide also damaged the nuclear power plant sites. This paper, along with a companion digital map database available at http://walrus.wr.usgs.gov/infobank/n/nii07jp/html/n-ii-07-jp.sites.kmz, describes the seismological and geo-engineering aspects of the event.