Small fast-moving flow-like landslides in volcanic deposits: The 2001 Las Colinas Landslide (El Salvador)

Abstract Fast-moving landslides are one of the most significant dangers deriving from slope instabilities. Landslides involving large volumes can develop in rock or debris avalanches with extreme mobility and enormous destructiveness. Nevertheless, a relevant number of casualties and damages derive from small, fast-moving landslides with flow-like behaviour. The Las Colinas landslide occurred at Santa Tecla (El Salvador, Central America) during a strong earthquake. It slid off the northern flank of the Balsamo ridge, and resulted in almost 500 casualties and can be considered one of the most destructive landslides ever known. Earthquake shaking was amplified by the rock mass and the steep ridge topography. We collected original geological, geomorphological and geophysical data in the Cordillera del Balsamo area. The involved materials, ranging from lapilli to tuff layers of different strength, have been mapped and characterized. Slope stability analyses have been performed both under static and dynamic conditions through limit equilibrium and finite element methods. Hazard zonation for this type of landslides requires the forecast of the movement velocity and final deposition area. We used a fully two-dimensional FEM model to simulate landslide spreading downslope. The developed code allows the use of different constitutive models and yield rules with the possibility to model and study internal deformation of the landslide mass, as well material entrainment and deposition.

[1]  J. Bommer,et al.  Geologic and engineering characterization of Tierra Blanca pyroclastic ash deposits , 2004 .

[2]  The San Salvador Earthquake of October 10, 1986—Seismological Aspects and Other Recent Local Seismicity , 1987 .

[3]  H Chen,et al.  Numerical simulation of debris flows , 2000 .

[4]  Oldrich Hungr,et al.  A model for the runout analysis of rapid flow slides, debris flows, and avalanches , 1995 .

[5]  Giovanni B. Crosta,et al.  Replay of the 1987 Val Pola Landslide, Italian Alps , 2004 .

[6]  B. Voight.  Rockslides and avalanches , 1978 .

[7]  S. Self,et al.  A comparison of pyroclastic flow and debris avalanche mobility , 1992 .

[8]  Y Nakamura,et al.  A METHOD FOR DYNAMIC CHARACTERISTICS ESTIMATION OF SUBSURFACE USING MICROTREMOR ON THE GROUND SURFACE , 1989 .

[9]  Julian J. Bommer,et al.  A New Digital Accelerograph Network for El Salvador , 1997 .

[10]  Tetsuro Yamamoto,et al.  LAS COLINAS LANDSLIDE CAUSED BY THE JANUARY 13, 2001 OFF THE COAST OF EL SALVADOR EARTHQUAKE , 2002 .

[11]  Christopher R. J. Kilburn,et al.  Runout lengths of sturzstroms: The control of initial conditions and of fragment dynamics , 1998 .

[12]  Richard M. Iverson,et al.  Flow of variably fluidized granular masses across three‐dimensional terrain: 2. Numerical predictions and experimental tests , 2001 .

[13]  R. L. Shreve,et al.  Leakage and Fluidization in Air-Layer Lubricated Avalanches , 1968 .

[14]  F. Legros.  The mobility of long-runout landslides , 2002 .

[15]  S. Evans,et al.  The Las Colinas landslide, Santa Tecla: A highly destructive flowslide triggered by the January 13, 2001, El Salvador earthquake , 2004 .

[16]  H. J. Melosh,et al.  The physics of very large landslides , 1986 .

[17]  Richard M. Iverson,et al.  Flow of variably fluidized granular masses across three‐dimensional terrain: 1. Coulomb mixture theory , 2001 .

[18]  D. M. Cruden,et al.  Chapter 2 - Frank Rockslide, Alberta, Canada , 1978 .

[19]  W. Salazar,et al.  Earthquake Disasters of 13 January and 13 February 2001, El Salvador , 2003 .

[20]  P. Habib,et al.  Production of gaseous pore pressure during rock slides , 1975 .

[21]  Theodor H. Erismann,et al.  Dynamics of rockslides and rockfalls , 2001 .

[22]  Adrian E. Scheidegger,et al.  On the prediction of the reach and velocity of catastrophic landslides , 1973 .

[23]  Giovanni B. Crosta,et al.  Numerical Modeling of Large Landslide Stability and Runout , 2003 .

[24]  B. Voight,et al.  Continuum simulation of flow failures , 1991 .

[25]  A J Hendron,et al.  The Vaiont Slide: A Geotechnical Analysis Based on New Geologic Observations of the Failure Surface, Volume 1: Main Text , 1985 .

[26]  Charles S. Campbell,et al.  Self-Lubrication for Long Runout Landslides , 1989, The Journal of Geology.

[27]  Giovanni B. Crosta,et al.  CONTINUUM NUMERICAL MODELLING OF FLOW-LIKE LANDSLIDES , 2006 .

[28]  Analysis of the spatial and temporal distribution of the 2001 earthquakes in El Salvador , 2004 .

[29]  G. Crosta,et al.  Numerical simulation of dry granular flows: From the reproduction of small-scale experiments to the prediction of rock avalanches , 2000 .

[30]  T. H. Erismann,et al.  Flowing, rolling, bouncing, sliding: Synopsis of basic mechanisms , 1986 .

[31]  Pierre-Yves Bard,et al.  Numerical and Theoretical Investigations on the Possibilities and Limitations of Nakamura's Technique , 1994 .

[32]  Julian J. Bommer,et al.  Earthquake-induced landslides in Central America , 2002 .

[33]  J. N. Hutchinson,et al.  A review of the classification of landslides of the flow type , 2001 .

[34]  Oldrich Hungr,et al.  The debris of the Frank Slide and theories of rockslide–avalanche mobility , 1986 .

[35]  Timothy R. H. Davies,et al.  Spreading of rock avalanche debris by mechanical fluidization , 1982 .

[36]  R. White,et al.  Destructive upper-crustal earthquakes of Central America since 1900 , 1993, Bulletin of the Seismological Society of America.

[37]  Timothy R. H. Davies,et al.  A fragmentation-spreading model for long-runout rock avalanches , 1999 .

[38]  J. Bommer,et al.  The El Salvador earthquakes of January and February 2001: context, characteristics and implications for seismic risk , 2002 .

[39]  W. D. Pennington,et al.  Seismicity and tectonics of the subducted Cocos Plate , 1984 .

[40]  Francesca Pacor,et al.  S-Wave Site-Response Estimates Using Horizontal-to-Vertical Spectral Ratios , 1997 .

[41]  Kenneth J. Hsü,et al.  Catastrophic Debris Streams (Sturzstroms) Generated by Rockfalls , 1975 .

[42]  J. Cepeda,et al.  Strong-motion characteristics of January and February 2001 earthquakes in El Salvador , 2004 .

[43]  G. Plafker,et al.  Chapter 8 - Nevados Huascarán Avalanches, Peru , 1978 .