Summary of the discussion on the use of fault zone maps
Fault zone map:
The fault zone map of Tehran, as well as the cities of Tabriz, Mashhad, Karaj, Kerman, and Zanjan, has been approved by the Supreme Council for Urban Planning and has been notified to the municipalities, but the maps, their scientific reports, and clear practical definitions of fault zones are not available to the public. Preparation of maps for 33 other cities is under study.
Introduction to zones:
In the fault zone map of Tehran, the types of fault zones are divided into 3 categories of main, medium, and minor fault zones. In the construction instructions in fault areas, zones are divided into 4 types of zones with very high risk, high risk, medium risk, and low risk based on the calculation of fault deformation with a very approximate relationship. Documentation for this division is not available.
Definitions:
According to international literature, the setback is a zone on the sides of a fault or rupture zone where any significant construction is prohibited (for example, about 20 meters). The fault rupture zone is a possible zone for surface faulting (for example, 300 meters). The near-field is a zone where the vertical acceleration of an earthquake is also considered (for example, at a distance of 5 to 15 km from the fault). Clear definitions need to be included in future editions of the guidelines.
Restrictions on fault zones in Iran:
The construction of buildings of great importance (such as hospitals) in the entire fault zone and buildings of great importance (such as schools) in parts of the fault zone has been declared prohibited. Buildings of medium importance (such as residential) can be constructed by applying the following measures:
(a) Respecting the maximum number of floors according to the hazard level (6 or 8 or 12).
(b) Respecting the maximum dimensions (40 meters).
(c) Respecting the large rupture joint or distance from the adjacent building or soil.
(d) Use of wide foundation.
(e) Observe a distance of 5 meters from the fault.
This type of restriction is unprecedented in the world for fault zones and lacks research support.
Practical suggestions:
If the land is in fault zones, site-specific studies should be carried out according to the methods included in the appendix to the guidelines to carefully examine the risk of faulting. Approved fault zones are wide enough to be safe, but on the other hand, even a 12-story building can be built in them and the non-construction zone is only 5 meters on each side of the fault. This guideline may not have any advantage in terms of improving fault safety and only imposes a number of unnecessary restrictions such as large discontinuity joints and wide foundations in a large area. An urgent revision of this guideline seems necessary. Reference to it in the new edition of 2800 should be made only after amendments.
Construction on a fault:
Research on building on faults should continue within the country and the results of global research in this field should be followed, because the results of this type of research can be used to retrofit buildings built on faults. Also, perhaps replacing the fault boundary method with other methods can be considered in future editions of the guideline. The structure can be effective in faulting depending on the fault angle, type and depth of sediments, so it is necessary to pay attention to this point of view.
Dr. Ali Fakher,
Professor, Faculty of Civil Engineering, University of Tehran
October 1403
P.N.: This summary is the result of the participation of various friends on his channel from August 17 to mid-October 1403.
@AliFakherChannel
@Earthquake_Engineering1
This post is written by Alireza_MoghadamNejad