Previous evaluations of regional liquefaction hazards identify several geologic and hydrologic factors that influence the susceptibility of a deposit to liquefaction, including (1) the age and depositional environment of the deposit; (2) the relative consolidation of sands and silts; and (3) the local depth to ground water
Can you outline these procedures in preparation of liquefaction hazard map? If you have developed relationship in each stage stated clearly?
What are the procedure for preparation of liquefaction susceptibility map?.
Hi!
Normally, the terrain with liquefaction should have a high degree/layers of clay interposed with other geological layers. Firstly, is important the behavior of these clay layers to the groundwater. So, you need the hydrogeological map and some piezometers to see the water table level. Secondly, you need to determine the main factors which may trigger the liquefaction in your area: could be an earthquake or a landslide, massive constructions, tunnel perforations etc.
For the mapping, the ArcGIS software is undoubted the best tool, but you don't know where the shear stress will be in your critical area.
So, to incorporate a problematic layer/risk layer into GIS to generate a Spatial Hazard Map, I suggest to you to use a modelling program to complete a preliminary analysis of the possible landslide, 'open-fracture' or earthquake. The lab tests of the rock/soil samples from the site could be an alternative to identify the shear strength in different location and further you can try to do a geo-statistical analysis for whole interested area.
Many thanks!
Margarit
The section of this report that deals with the liquefaction hazard map has a step by step description of the process. If you explore the publications at the same website, you will find subsequent reports applying the same basic approach, but with increasing reliance on GIS and other computer automation.
http://www.oregongeology.org/pubs/gms/GMS-079.pdf
To prepare a susceptibility map to liquefaction you need Geological, hydrogeological and geotechnical data: (1) You need a detailed (1/5000- 1/1000) geological map where non compacted recent geological units should appear on the map (ancient compacted deposits are not liquefiable, (2) You need a detailed geotechnical map based on in situ and laboratory tests, mainly the granulometry of the deposits (liquefiable deposits should be fine sand with less 20% of clay), (3) You need the hydrogeological map of the area (liquefaction occurs only if the table water is at depth of less than 12m). See also the following references: Youd and Perkins (1978), Youd (1998).
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