| Popis: |
Two subsidence phenomena occurred in February 2007 and May 2010 in the urban area of Guatemala City. Both episodes were located over the western drainage main collector. The first one presented 25 m diameter and 60 m depth; the second 27 m and 48 m respectively; human casualties and urban damages resulted from these incidents. An Electric Resistivity Tomography was carried out along the collector trace with three different arrays (dipole-dipole, Wenner-Schlumberger, and Wenner). A total of 1,777 m were measured and distributed into six different profiles, ranging between 110 and 960 m, with an investigation depth ranging between 30 and 100 m. It is possible to observe several areas that could represent a risk to urban facilities. There are high resistivity anomalies related to a poor volcanic consolidated material, with presence of gas or high probability of irregular caves. Also highly water saturated zones suggested from the observed anomaly geometry. The water flow seems to follow the direction of natural topography which decreases from West to East. In case that the interstitial water flows away, it would leave an empty porous media, triggering a liquefaction process and a probable subsidence process. |
