Lesson 10: Non-Structural Hazards

Note: This question is intended to promote critical thinking about the situation itself (being in a gymnasium or other large room during an earthquake) and also to draw attention to the nature and limitations of decision-making processes that often occur between young friends in emergency situations. The overall goal is to empower each student to independently evaluate the situation, choose a course of action, and make the best possible decisions to ensure their survival. This includes situations wherein students are given poor advice from friends or adults. The scenario has a variety of important details that can be discussed. Below is only a summary of some of the main points regarding earthquakes and non-structural hazards. Students are likely to point out a number of things about this situation that may not be covered below. Please discuss all comments that the students suggest, emphasizing the importance of maintaining situational awareness and critical thinking throughout the earthquake emergency.

Potential answers: People are sometimes able to hear earthquakes when earthquake waves travel through the ground. P-waves are sound waves and while their tones are generally too low to be heard by humans, earthquakes can sometimes generate sound waves in the audible frequency range before any noticeable physical movement is noticed. Other indications include the shaking overhead lights and the shaking trees outside. Hanging or tall objects can be sensitive to small movements of the ground.

Reza does not seem too concerned about the earthquake. While panic is not the best reaction, and it is generally said that it is a good thing to remain calm during a potentially dangerous situation, Reza seems a little too calm for this situation. One can be in a state of readiness and alertness about the situation without being panicked.

Reza might be saying these things because he was taught to think this way by someone, or because it seems reasonable to him based on his previous experiences with earthquakes that haven't been particularly destructive. Alternatively, Reza might be saying this because he doesn't want to seem like a coward, or to cover up for the fact that he is nervous and doesn't really know what to do.

Regardless of his motivations for behaving this way, and regardless of the actions (or inactions) of the teacher, Reza's suggested course of action is not advisable. No two earthquakes are ever the same. Just because other earthquakes in the area may have seemed similar to this one (and may not have caused much destruction), this earthquake could easily unfold into a larger earthquake without warning. There is no way to tell whether this earthquake will be destructive before or during its occurrence.

There are many structural and non-structural hazards in this situation. While the earthquake does not seem powerful enough to destroy the gymnasium, there is no way to know this for sure. A small construction defect or a resonance of the gymnasium structure may induce large movements of the building or other fixtures within the room if the earthquake is producing waves near the natural frequencies of objects in the room (for definitions of natural frequency and resonance, see Lesson 9). The lights swinging back and forth are a perfect example. If the lights become detached, they could easily fall or the glass in the lights can break and fall down on students.

The trees shaking outside are also a potential hazard. They can produce falling branches, or the trees can swing over and hit the windows if they are close enough to them, causing the windows to break and showering glass inside and outside the gymnasium. Most glass windows are very brittle (for a definition of brittle, see Lesson 3) and will break free of their supports with only slight disturbances given their fragility. Glass windows can also break if the building itself begins to shift a small amount during an earthquake.

Because of these risks, it is best in general that the students leave the gymnasium as quickly as possible, taking care to avoid the large glass windows and trees outside if possible. Better to be safe, even if the earthquake is small, than to wait and see if a large earthquake is going to put the students in danger before they can react. Remind the students that during very strong earthquakes it is difficult or impossible to remain standing, let alone walk or run to safety. Even a short distance such as 30 meters to an exit or entrance may be a false comfort if the earthquake does become very strong.

Although these objects were not mentioned as part of the scenario description, there are other common objects found in a gymnasium that may cause a hazard. These may include suspended fixtures (e.g., basketball hoops, volleyball net polls) or electrical fixtures (e.g., large lights, loudspeakers).

Please reference Picture Group 1 to study actual scenes of damage within gymnasiums and other community areas in schools in Japan.

Farbod was in the library on the second floor of the school studying for his science report. He liked being in the library during the summer because it is the only room in the school with a large air conditioner mounted in the window (the air conditioner helps protect the books during the hot summers from damage due to humidity and temperature changes which affect the paper in the books). There was also a large TV on a rolling cart in the library near the door, which the librarian sometimes let Farbod use to watch interesting science videos and generally kept in the back room.

When the ground started shaking, Farbod didn't immediately know for sure what was going. He was in the reference section of the library looking through the encyclopedias and map books. The first thing he noticed was that it felt like a big truck was going by outside, so he didn't give it much thought. Then he heard strange creaking noises among the tall wooden bookshelves as though somebody was standing on top of the bookshelf in front of him and trying to move it back and forth.

Farbod went to the end of the bookshelf toward the central part of the library to see what everyone else was doing as well as find out what was happening. He saw the librarian and other students looking out the window trying to see if a big truck or airplane was causing the strange noises. They saw the trees shaking in front of the gymnasium and somebody yelled, "It's an earthquake! The ground is shaking!"

Potentional answers: Yes, Farbod is exposed to hazards in the library. He is exposed to the non-structural hazards in the library and any that might exist throughout the school along the escape route to get to a safe location. Farbod is on the second story of the school, which means he is also exposed to the structural hazards of being within a multistory building.

There are windows which can easily shatter during an earthquake, so the teacher and the children looking out the window are also exposed to hazards. In libraries, the bookshelves are often completely filled up with books, so that any slight movement of the bookshelves tend to cause books to fall off the shelves or cause the bookshelves themselves to fall over. This may have been what caused Farbod to hear the creaking sounds among the bookshelves. Students should keep in mind that if just one bookshelf falls onto another bookshelf, this may cause all the bookshelves to fall, one after the other.

There are also other hazards in the room, such as the large television on the rolling cart. The television is probably not secured very well to the cart, and the cart can easily move or fall over since it is not bolted to the ground. It is mentioned that the cart is near the door, which means that students can be harmed if the cart begins to fall over as they are leaving the room. Moreover, the fallen television may get in the way of students trying to leave if it topples onto the floor before the students are able to leave the room.

Another hazard that exists for students outside of the building is the air conditioner that is mounted in the window. Oftentimes, these units are not well-secured to the building or the window frame. They are often balanced or perched in the window frame with little or no structural support. Air conditioners like this often fall out of windows onto the building or sidewalk below during an earthquake.

Farbod should be very vocal about the hazards he sees that may endanger the teacher and students around him. In any earthquake, the best idea is to get to a safe location as soon as possible, regardless of the perceived strength of the earthquake. A slight shaking at first can very easily turn into a very powerful earthquake with little or no notice.

Please reference Picture Group 2 to study actual scenes of damage within libraries in schools in Japan.

After leaving his friends at the school entrance, Amin went to chemistry class. That day, the class was studying a chemical reaction that involved the heating of reactants. Heating reactants was always his favorite part of chemistry experiments. He also enjoyed delicately handling the reactants, which could easily burn his skin if he were not careful. He was wearing eye protection goggles and a lab jacket to protect his clothes from the chemicals used in the class. Each group of students in the class had small flame stands (a Bunsen burner) at their table that hooked up to a gas tank in the back of the room through a series of tubes and valves, the latter of which could be seen running along the pipes and electrical wiring mounted near the ceiling in the classroom.

Amin was at the back of the room washing the glassware that he was using to do the experiment when he heard a noise that sounded like a truck going by. He also heard the tinkling sounds of the chemistry glassware in the cabinets around him. He kept washing his glassware, but the sounds did not go away. His chemistry teacher then yelled, "Earthquake! Students exit the school immediately. Assemble at the street corner in front of the school." The teacher continued giving instructions as the students left: "Move quickly but remain calm, do not take anything with you from the class and do not stop elsewhere in the school on the way out."

Potential answers: The chemistry teacher needs to be aware of the numerous special hazards that are present in the classroom. If the chemistry glassware can easily fall out of the cabinets, then even a small earthquake would cause the glass to fall and break on the floor, which could slow or prevent some students from leaving the room (depending on the footwear that the students are wearing). If something falls on the gas tubes going from the gas tank to the burners throughout the room, then a leak could release gas into the classroom. This could cause a fire hazard or possibly illness or loss of consciousness to any trapped students if they are forced to breathe this gas. The teacher should have a fast means of shutting off the gas and securing the gas tank in an emergency, and the students should be educated in the location and use of these devices in case the teacher is not present or somehow unable to secure the room during an emergency. Any damage to the electrical wiring or pipes that are mounted near the ceiling could expose students to high voltage or hot, cold, or waste water from broken or leaking pipes.

The chemistry teacher seems to have been prepared to respond to an emergency situation much better than the teachers that Farbod and Reza were with. The messages that the chemistry teacher yelled were clear, concise, and in descending order of importance: the problem was identified, followed by a simple command to move to a safe destination, and finally ended with commands to make sure that the students did not stop until they reached the safe destination for any reason (e.g., gathering personal belongings). While there may be some places in the school where the safest option is to shelter-in-place, a room with gas lines, pipes, electrical wiring, and glassware is not likely to be one of those places. The important point to note is that the teacher was prepared to recognize and act in a dangerous situation with clear instructions for the students. Students and teachers in any part of the building should be prepared to make the safest decision depending on the circumstances and layout of the school.

Please reference Picture Group 3 to study actual scenes of damage within special facilities of classrooms in schools in Japan.