英訳：

Dear Prof. Otani, it was a surprise to hear from you. Up to know we have no more information that this you have, but I will try to get some more information and send it to you as soon as possible. This is the (my?) translation.

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It was a pleasure to hear from you again. I will make a brief resume of the earthquake.

Location:

The epicenter was located about 20 km from Armenia City, the earthquake was generated due to the rupture of one branch of Romeral fault, the same fault that provoked the Popayan earthquake on 1983. The focal depth was between 25 and 30 km, this data is yet to be confirmed based on the study of the aftershocks taken by the local instrumentation network, which was installed just after the occurrence of the earthquake.

Magnitude and intensity:

The average magnitude (?) in a similar scale to the ML, can be considered around 6. The local intensity has been taken very high in some places, specially in the upper part of the mountains where regular quality constructions were built. I estimate or assume that the local intensity there could be something between VIII and IX on Mercalli scale. In other parts of Armenia City, the intensity was under VIII. As always, if there were not enough care on the evaluation process, somebody could have said that in some zones the intensity reached XII because all around was destroyed. But we should be conscious that all the edification in that zone was really weak, and probably a more detailed study could change the initial opinion obtained from eagle view. In Pereira City the maximum intensity could have reached VIII in zones where the subsoil was made by material fill, in which always had occurred severe earthquake damage. Some small towns where the edification are made principally with adobe, were almost totally destroyed. The main earthquake displacement registered was horizontal-left with a very small transversal component, which indicates that there is a NS displacement of the Andino-block (plate?) with respect to the east plain. I think that we already had postulated this phenomenon 25 years ago.

Consequences:

Up to now there are more than 1000 counted cadaver, but what I saw yesterday in Armenia City showed that even now there are more cadaver under the rest of entire house settlement that were destroyed. In Armenia City multistory buildings of structural reinforced concrete were also severely damaged. Some of them collapsed and trapped their occupants. There were so many damaged buildings that it is required the demolition of large zones with old RC buildings with very bad and inadequate reinforcing details, that is to say lack of confinement (lateral reinforcement) and deficient materials. This can give you an idea of the situation. Yesterday, during an inspection that we (various from the Andes) made, we ordered the demolition of 92 edification over 120 revised. The most affected are located in the vicinity of a small canyon, which flow is controlled by a tube structure covered with earth-fill. I estimate that the damage can reach approximately 1,000,000,000 US dollars, but it is still too early to try to be precise.

Accelerations:

There are ground motion records that I am sure Julio will bring with him for you. I saw some of them in field. In Pereira City, in natural field there were registered accelerations of about 0.3g, while in rock could be of around 0.1g. I could not see the total records because our mission was to help defining which edification could be used, which of them should be left while the retrofitting process is going on, and also which of the edification should be demolished. But there will be more information and we will send it to you.

From my point of view, the most serious task in consequence of this earthquake, is that in Colombia there are more than one million of refugees due to the internal war, which has become bigger in the last days. Most of these refugees will go to the disaster zone waiting for the big investment that the government has to do. Maybe it will appear a big social problem which could make more complicated the situation of the Country.

Conclusions:

The edification built with the building code behaves very good. The code is good, I think, as a lot of people think and the earthquake demonstrated it. Bad construction fell down or were severely damaged as it has occurred everywhere.

Mete A. Sozen

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Best regards to you and all the people from your lab.

Oscar Lobez

CENAPRED