AMEC seismic experts tapped for Haiti earthquake investigation

15/02/2010


Oakland, Calif. USA (16 February 2010) AMEC, the international engineering and project management company, announces today that two of its seismic experts are assisting in the development of a scientific report on the Haiti earthquake's geotechnical effects following a journey to that country earlier this month.

Senior Geologist Donald Wells and Senior Geotechnical Engineer Jim French, both from the AMEC Geomatrix office in Oakland, Calif., are members of a Geo-engineering Extreme Events Reconnaissance (GEER) team that conducted a six-day investigation of the Jan. 12 earthquake.

The 11-member team, supported by the National Science Foundation and led by University of Texas at Austin Prof. Ellen Rathje, performed reconnaissance investigations of the earthquake's ground-movement effects for a report to the professional community. The GEER team seeks to further engineers' understanding of what happens during an earthquake as part of the U.S. National Earthquake Hazards Reduction Program (NEHRP).

"We worked in the port area to document the damage, in Port-au-Prince to catalog building damage, and further west from Leogane along the coast and inland area near the fault that ruptured," said Wells. "We've mapped and observed many locations where road damage has occurred due to settlement of road fill in soft ground or to slumping of embankments around culverts."

"Along the coast, acres of ground have disappeared into the ocean in several locations due to extensive liquefaction and lateral spreading," Wells added. Liquefaction occurs when ground shaking reduces the strength of sand or sediment, causing it to become saturated with water. Lateral spreading is the result of differential lateral and vertical movement in overlying soil and is a principle cause of liquefaction-related earthquake damage. Wells noted that at several areas where liquefaction occurred, the team performed cone-penetration testing and spectral analysis of surface waves testing, both of which are used in evaluating liquefaction hazard.

One surprising result of investigations by the GEER team and other reconnaissance teams is that the fault that is presumed to have caused the earthquake "- the Enriquillo Plantain Garden fault "- did not rupture to the ground surface. "We traversed the fault in numerous locations and confirmed it did not move at the ground surface," Wells said. Newly exposed coral reefs were observed along the coast, indicating the fault rupture may have uplifted portions of the coast north of the fault.

"The devastation to structures and lives clearly was a result of poor-quality design and construction," French said. "We have the knowledge to design structures to survive the levels of ground shaking experienced in Haiti, but this knowledge was not put into practice in most of the collapsed buildings."

Extreme events engineering is an experience-driven field where immediately following an earthquake, tsunami, hurricane, landslide or flood, perishable data that can be used to advance our understanding is systematically collected. Field observations are particularly important in the area of geo-engineering since it is difficult to replicate in the laboratory soil deposits build over thousands of years. Detailed mapping and surveying of damaged areas provide the data for case histories that drive the development of many design procedures used by engineers.

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