Ingeniare. Revista chilena de ingeniería, vol. 18 Nº 1, 2010, pp. 154-155

EDITORIAL

IT IS TREMBLING... 

The dawn of Saturday February 27th, was passing by as a typical summer weekend night (in this case, the last weekend of my vacations). We had recently returned from Algarrobo and we were re-adapting to the life of Santiago. Suddenly, at 3:34am, it began the strongest earthquake in many decades. My wife awoke me, but we had some problems in understanding what was going on and where exactly we were. I believe we spent a couple of minutes just sitting on our bed observing how different objects were noisily falling down. The electric power was interrupted within a few seconds after the earthquake started, and the earthquake still had some energy left when we were trying to get out of the house. Of course, the lanterns we have for these situations were not within our reach, so in the middle of the darkness we managed to find a few candles and so got some light in order to find our lanterns.

All our fixed wireless phones, certainly, had turned instantaneously into paperweight, for the lack of electricity. Luckily, my knowledge of telephony reminded me that the wired old traditional telephones worked, and still do, using energy provided by batteries located at the switching exchanges, which can support the wired telephone system operating normally for more than 24 hours.

Therefore, as a precaution, we have stored somewhere in our house an old standard telephone (of those which connects to the telephone network through a couple of wires). So, after extracting this antiquated wired telephone, from its coffin, we connected it to a telephonic terminal and, certainly, it worked flawlessly. Meanwhile, our cellular phones were desperately and uselessly trying to connect to the ones of our family. This was a useless enough effort, since also my knowledge of telephony reminded me that the degree of service of a cellular system, it is based on a normal behavior pattern of the users and a typical geographical distribution of those. So, the cellular system (and also the wired telephony system) is designed for the traffic conditions occurring in the rush hour (i.e. in the period between 10:15am and 11:15am, for example). In such a period, the users of the cellular system are in their works, schools, etc., and not at their bedrooms. It should be noted that the grade of service of a cellular service is designed with an objective of 2% (that is, 2 over 100 calls are not completed). Furthermore, the cell area is defined in terms of the expected number of wireless phones which will be, at a given time, within the cell area. Of course, that cell area in residential zones is clearly larger than the cell area required in zones such as downtown Santiago, due to the larger number of cellular phones offering traffic to the system. The expected and obvious result was that the cellular system collapsed at once, due to the sudden increase on the offered traffic which clearly surpassed the design capacity of the residential area cell. Not so obvious, but equally notable, is the fact that the wired telephone systems, which use the infrastructure of cable television systems, also fell down irremediably, in this case for the lack of electric power.

We were worried by our children, which live in the tenth floor of an apartment building. However, only 10 minutes after the earthquake stopped, we felt quite relieved, when our faithful old wired telephone ringed and my eldest daughter (again, calling from a wired telephone) told us they were all fine (since they had spent the night an a party in the house of a friend, and at the floor level, instead of the 10th floor).

Old traditional radio stations, again, faithfully complied with their assignment and, just minutes after the earthquake, went into the air with the first news of the catastrophe. It was observed, again, the importance of having a cheap battery feed AM/FM radio receiver, condition which, by the way, we did not comply so we had to use the radio of our car.

Of course, for several days in Santiago, it was difficult to be communicated through the wireless telephone system.  It was clear that the cellular telephone system did not have energy supply backup to the same level of that of the large batteries banks on the switching offices of the wired telephone system and, therefore, they were very dependent on the availability of electricity.  Even so, some cellular telephone operators had fewer problems than others and the analysis of those experienced problems will be fundamental to prevent them occurring again in future catastrophes.

Is it reasonable that these communications problems had occurred?  Well, in the given context it was something to be expected, since these communications systems are designed for normal operation conditions, and those conditions do not include special situations, such as the ones presented each new year’s eve and, much less, those occurring after a strong earthquake occurring once every 25 years. A little more debatable is the observed collapse in the operation of the cellular telephone system and the unexpected long time period that it took to recover its normal operation.  Knowing the very broad coverage of this cellular telephone system, it is justified to study ways to improve its reliability in those emergency situations.

It has been suggested, by some of the cellular operators, that a possible better scenario would be, in these emergencies, to degrade the voice service in favor of giving better support to the sending of text messages through the cellular system. However, it shoud be studied the percentage of users of the cellular system which actually use the cellular message service and, probably, to make a public campain in order to teach how to use these text messages in an emergency situation.

After some six hours without electric power at our home, it was restored and we could return to a certain degree of normality, including Internet availability.  Amazingly, and paradoxically, we received on the same Saturday a pair of calls (through Skype) of some friends in the US and Saudi Arabia, and many more e-mail messages, expressing the concern that this catastrophe generated everywhere while, at the same time, it was only after three days that we had telephone contact with my brother, who happens to live only a few kilometers away here in Santiago.

It was also put in clear evidence, the need that all the agencies, that should respond in these emergency situations, should have communications devices independent of the availability of electric power or a connection network, as the satellite telephones provide.  We believe that it is necessary to study all the different catastrophe scenarios, regarding the communication needs and to make all the required investments, so that those emergency agencies can get the relevant information the same instant the catastrophe happens.  It was an unacceptable situation that, after a tsunami had occurred in a large city as Talcahuano just 15 minutes after the earthquake, the information of that event was known in Santiago only several hours later, with the by all already known results.

PhD. Miguel Ríos Ojeda
Departamento de Ingeniería Eléctrica
Escuela de Ingeniería
Pontificia Universidad Católica de Chile
Valparaíso, Chile
mrios@ing.puc.cl