MONITORING SEISMIC DAMAGE TO BRIDGES AND HIGHWAYS WITH GPS: INSIGHTS FROM THE 1994 NORTHRIDGE EARTHQUAKE

The 1994 Northridge earthquake permanently deformed the ground surface in the Los Angeles urban region, increasing the elevation of the ground by as much as 20 in. (50 cm), and changing horizontal positions by up to 8 in. (20 cm). The network of geodetic monuments used by engineers and surveyors was thus distorted and rendered inaccurate. The monuments are used for construction and monitoring of the urban infrastructure, including dams, levees, aqueducts, and storm drains; bridges, buildings, and heavy machinery; road and rail transportation routes, communication conduits and pipelines; and property boundaries. We resurveyed the height of 979 leveling bench marks (BMs) and the positions and heights of 66 Global Positioning System (GPS) monuments; emplaced 252 new BMs where the previous monuments were lost or unrecoverable; and added 128 new GPS monuments spaced 5 km apart along critical highways for rapid damage assessment to the main traffic arteries after future earthquakes. In total, 496 monuments were added to the national network. In addition to permanent deformation, the Northridge earthquake strongly shook the ground, with peak shaking exceeding the acceleration of gravity and with peak ground velocities of 65 in./sec (165 cm/sec). Such sustained shaking and high ground velocities damaged structures and caused surface cracking, liquefaction, ground slumping, settlement, and landslides, which also contributed to damage. Because half of the existing BMs and GPS stations are located on engineered structures, their displacement records not only the permanent change in height caused by the earthquake, but also any disturbance of the structures caused by shaking. We developed a geophysical model of the permanent earthquake deformation that is consistent with the movement of the geodetic monuments. All BMs with displacements that differ from this model by more than 1.2 in. (3 cm) are identified as anomalous. Of the 40 such anomalous or disturbed BMs, those in engineered structures include railroad and highway bridge abutments and spans, tower and building foundations, catch basins, retaining walls, and culverts; the remainder are typically in engineered fill.

• Corporate Authors:

  California Department of Transportation

  1120 N Street
  Sacramento, CA  United States  95814
• Authors:
  • Stein, R S
  • Hudnut, K W
  • Satalich, J
  • Hodgkinson, K M
• Conference:
  • Second National Seismic Conference on Bridges and Highways
  • Location: Sacramento, California
  • Date: 1997-7-8 to 1997-7-11
• Publication Date: 1997

Language

• English

Media Info

• Features: Figures; Photos; References; Tables;
• Pagination: p. 347-360

Subject/Index Terms

• TRT Terms: Benchmarks; Bridges; Deformation; Earthquakes; Geodetic surveying; Global Positioning System; Highways; Monitoring; Seismicity
• Identifier Terms: Northridge Earthquake, January 17, 1994
• Uncontrolled Terms: Bridge damages; Geophysical models; Highway damage
• Subject Areas: Bridges and other structures; Design; Highways; I24: Design of Bridges and Retaining Walls;

Filing Info

• Accession Number: 00760108
• Record Type: Publication
• Files: TRIS, STATEDOT
• Created Date: Feb 2 1999 12:00AM