(R.J.) “I think this bone goes right here. It looks like it’s part of the tail.”
(Bianca)Wrong it’s actually part of the head.
(R.J.)O.k. This is the closest we’re going to get to a dinosaur dig.
(Bianca) Jacob is going to have so much fun looking for dino bones.
(Anthony) Excuse me, they’re called fossils.
( Starts to feel the shake)
(Bianca) Did you feel that?

(Anthony) Huh?
(R.J.) I did. What could it be?
(Second Shake)

(Anthony) I felt that one.
(Bianca) Now that you’re with us, what do you think it is?

(Anthony) It’s an earthquake!
(R.J.)Don’t jump to conclusions. Go to the NASA SCI Files web site and see if they have any information on earthquakes.
(turn to camera) Visit the research rack on the NASA SCI Files web site for resources on earthquakes. I found two places in Virginia where seismologists record earthquakes.
( Bianca) A size what?
(R.J.) A seismologist is somebody who studies and measures earthquakes.

(Tony) Look , a seismogram is located near us at the Tidewater Community College. ( Reading from screen) Let’s call
Seismologist, Michael Lyle.

Dr. D: We’ve never been there, but we think that it’s made of iron and nickel. The inner part of the core is solid and the outer part is liquid. It is so dense that if you had a gallon (showing gallon) jug full of the Earth’s core material, it would weigh over a hundred pounds!
(Anthony)Wait a minute Dr. D. You lost me. How do we know how big the core is and what it’s made of? How do we know when we’ve never been there!?
Dr. D: Well, it’s just a guess.
(Anthony)You’re kidding
Dr. D: Actually it’s a pretty good guess based upon a lot of evidence. One of the biggest clues to the Earth’s structure comes from the study of earthquakes.
(Bianca)So we’re using earthquakes to help understand earthquakes?
Dr. D: That’s right. The part of the peach that you eat is what we call the mantle of the earth. It’s not as dense as the core, but it’s denser than what is on the outside.
(Catherine)What’s the outside called?
Dr. D: It’s called the crust.
(Bianca)Just like a crust of bread.
Dr D: Very good. The Earth’s crust is very thin. The crust under the oceans is typically between 5 and 10 km thick and is made of dark dense rock called basalt. The continental crust is about 30 to 70 km thick and is made of a lighter, less dense rock like this granite.
(Anthony)Is there a reason why the Earth is layered like this?(Dr. D) It’s because of density. Watch this experiment. I’m going to put some green tinted water and some salad oil into this graduated cylinder and shake them up. Let’s see what happens.
(Anthony) Thee salad oil is on top, and then the water.
Dr. D: Now let’s add some motor oil. It turns out that the least dense, the motor oil, is on top, and the densest, water is on the bottom. That’s just what happened in the early history of the earth when it was all liquid.
(Catherine) Earth liquid? Strange, but what’s this have to do with earthquakes?
Dr. D: The crust on the outside of the earth is rigid and brittle. It is broken into about 12 segments that we call plates- like this cracked boiled egg. These plates float on the more dense but flexible mantle below- kind of like this egg white. They are in continual movement.
(Anthony) Wow, this is too weird. Why don’t we feel them moving?
Dr. D: They move about as fast as your fingernails grow, which is only a few centimeters a year. But, we have fossil evidence of that movement that we call Plate Tectonics.
Anthony: Are fossils also a clue to understanding earthquakes?
Dr. D: Well, …, yes!

(Catherine) But, Dr. D, are there other things that can cause vibrations?
(Dr. D) That’s a good question. Anything that makes a very loud sound can make things shake a little.
(Bianca) I watched fireworks on the Fourth and some were so big, I did feel a vibration.
Dr. D: Oh no! I’m late for an appointment. Why don’t you stay here awhile and discuss this some more.
(Bianca) Ok. Bye Dr. D. What about a sonic boom? We learned from the Case of the Barking dogs that sonic booms create a noise because the plane travels faster than the speed of sound.
(Catherine) That’s it! We have our hypothesis. If Airplanes were flying faster than the speed of sound, then it would cause the ground to vibrate.
(Bianca) I don’t think a sonic boom is our hypothesis because I forgot that my dad says the military never flies faster than the speed of sound over land anymore.
(Catherine) Oh, I thought we had it.
(Anthony) I’m glad R.J. and Jacob are going to California for the Science Fair. Maybe they can research earthquakes for us.
(Bianca) Wait a minute. Jacob is in Utah looking for fossils. Dr. D said that there was fossil evidence of plate tectonics.
(Anthony). I wonder if that’s the same thing as the Continental Drift Theory my teacher talked about.
(Catherine) Maybe, but, I don’t understand what fossils and Plate Tectonics have to do with earthquakes?
(Bianca) Let’s E- mail Jacob and ask him to find the answers.
(Catherine) Okay. I’ll do it.
(Anthony) We need to do some investigating on our own. Let’s go back to the tree house and find out if anyone else has felt the vibration.

(Anthony) Done. Do you know what kind of dinosaur this is?
(Kali) Yes a ------.
(Anthony) Not bad. (Another tremor, dinosaur breaks)
(Bianca) What’s going on?
(Kali) I don’t know. But, I don’t like it!
(Anthony) Now, that was an earthquake!

(Bianca) How do you know?

(Anthony) It just felt like one.

(Kali) Maybe this is another construction blast. I’ll call KSNN again. ( Actor goes to make call)
(Anthony) Look. The dinosaur is destroyed. This will never get built.
(Bianca) Listen. We have bigger problems right now.

(Kali) KSNN just confirmed there were no reports of a construction blast. What could it be?
(Anthony) I don’t know. But, we really need to organize our thoughts. Let’s go to the problem board.

Lyle: I think Dr. D is down the hall building a seismograph.
Bianca: Dr. D. A seismograph! We’re there!

Dr. D: Because it gives an electrical signal, it is easy to amplify the signal so that even a small shaking can show up on the computer. Why don’t you take this seismograph back to the tree house and see if you can record another tremor.
Bianca: That’s great Dr. D. We’ll be prepared now.
Dr. D: I have a friend at NASA’s Jet Propulsion Lab in Pasadena, California who uses satellites to measure the movement of the earth’s crust from space. You might want to talk to her in your quest to be earthquake experts.

What’s Up?
What is GPS and how is it used?
What are P and S waves and how do they differ?
What are two types of scales used to measure earthquakes? We’ll find out next in the Case of the Shaky Quake

(Catherine) Cool! I can’t believe the GPS can detect 3 millimeters of movement from space!
(Catherine) Check this out. Come closer.
3 milimeters is only this big.
(Anthony walks in)

(Bianca) Hi Tony. We’re talking about GPS In the future, it might help us predict earthquakes.
(Anthony) Yeah that’s great, BUT, what about problem right now!
(Kali) Dr. Donnellan told us if there was an earthquake in Virginia seismographs would pick it up.
(Bianca) But, we looked at seismograms and we still don’t have a definite answer.
Let’s do some problem solving.
(Tony) I have an idea. Let’s call R.J. and Jacob.
(Catherine) Tell them Hi , I’ve got to go.
I have soccer practice today.
( All) Bye

(Tony) Hi guys! How’s California?

(R.J.) It’s great! Nice, Sunny and we’re also learning a lot at the science fair.
(Jacob) So you’re still trying to solve the tremor problem?
(Bianca) Yes, but, we need your help with the problem board.
(Jacob) Okay, let’s go to it.
(Kali) We know the second set of tremors was not related to the first set.
(R.J.) We know the plate’s movements can cause earthquakes and there are a lot of faults.
(Tony) We know there are faults in Virginia.
(Bianca) We also know other things can cause movement on the seismograph.
(Jacob) Like what?
(Bianca) The seismologist told us that quarry blasts, sonic booms, and thunderstorms can be mistaken for earthquakes.
(Jacob) Thunderstorms? Did you guys have storms that day?
(Anthony) It was cloudy and stormy that day. But, I don’t remember seeing any lightning.
(Kali) But, it did sound like a clap of thunder.
(Bianca) And that would register on the seismograms.
(Kali) Earthquakes don’t make noise so it must have been thunder. Maybe this is our new hypothesis? If there was thunder, then it would cause vibrations on earth.
(R.J.) Don’t throw away the earthquake hypothesis too fast. During my vacation, I’ve been researching earthquakes, and look I just happened to find these accounts of an earthquake in Oklahoma.
( reading accounts)
“I heard something like a loud clap of thunder or something exploding.
Here’s another one. “It sounded like a big truck and it rattled things in my house. .
(Anthony) Great job, Bud. Our competing earthquake hypothesis still survives.
(Jacob) I still think that we need to know if there was lightning and thunder that day
I’ll check with the Weather Service.
(Anthony) We never checked out what the seismologist told us about the p and s waves. I think we should; it might be a clue.
(R.J.) We can help you. We’re supposed to meet Dr. D and his friend, Dr. Tang at the California Academy of Science Museum to see the earthquake room. We can ask him.
(Jacob) Neat. I hope it’s not as real as the hurricane room.
(R.J) I’m sure that we can find out more about earthquake waves at the Museum.
(R.J.) Well. Let’s not just sit here. Let’s get to work.

Jacob: I hope that it’s not like the hurricane room that Bianca and Catherine went through. That must be Dr. Tang over there.

R.J. Dr Tang?
Tang : Tree house detectives?
Jacob: That’s us. Nice to meet you Dr. Tang
Tang: I understand you are interested in experiencing an earthquake.
Jacob; Well, I’m not sure about that. But, we do need to learn more about how experts measure the power of an earthquake.
Tang : One scale that scientists use is called a Richter Scale. It tells us the strength of an earthquake.
R.J. Are there other scales that scientists use?
Tang : Yes, scientists now prefer a more precise scale that’s called the moment magnitude scale. It gives a number to an Earthquake that tells us its total energy released. Jacob: What’s the number of “our earthquake”?
Tang Well, if it was an earthquake, people could feel , it would have to be at least a 2, A moderate earthquake would be about a “5”.
Jacob Wasn’t there a major earthquake here in San Francisco in 1906? What was its number?
Tang: Well, it was a 7.7, but to see what that means, you really ought to experience the earthquake.
R.J. I’m not sure I want to do that.
Tang :Don’t worry, it’s quite safe. We’re going to do it in our earthquake room here at the California Academy of Sciences.
Experience Quake Montage
R.J. Cool! It seemed so real. How do scientists know so much about it?
Tang:Well, we studied people’s diaries and looked at how different houses and churches were damaged and where the earthquake ruptured the ground around San Francisco during this time period.
Jacob I guess observations are important?
( Turn to camera) Your science journal might be valuable evidence one day.
Tang : Yes. Even today, with sophisticated instruments, scientists still want to hear what people experienced. Here take a look at this earthquake questionnaire.
Jacob: Wow! Look at this . They want to know was it difficult to stand or walk?
R.J And did objects rattle or fall off the shelf.
Jacob: Here’s a simple question. What’s your zip code?
R.J. Does it make a difference where you live?
Tang: The effects of an earthquake depend greatly on how far away you are from the source.
Jacob: You mean, the farther away, the less shaking you feel during a quake?
Tang : Yes, but it also depends on what the ground is like.
R.J.: What does the ground have to do with it?
Tang: Let’s look at this gelatin. If I push it even a little bit, it jiggles a lot. Now look at this rock. I can push it, but it doesn’t jiggle at all.
Jacob: I know where I would want to stand during an earthquake—on solid rock!
Tang: Yes, a house built on sand or mud would not do well in an earthquake. Jacob: Thanks so much Dr. Tang. You’ve given us a lot of good information.
(Tang) You’re welcome. Good luck solving your mysterious quake.
What’s Up?
Could a thunderstorm have caused the tremor?
Will P and S waves help solve the mystery?
What should the tree house detectives investigate next?
Don’t miss the conclusion of the case of the Shaky Quake!

JPL Interview

Kali: We got an e-mail back from Dr. Peter Brown. He says that it probably would take a meteoroid of at least several hundred kilograms, which is the size of a small chair, to produce a sonic boom strong enough to be recorded by a seismograph.
Bianca: Look at this. He also says that if large meteoroid has enough energy and gets deep enough into the atmosphere, it can produce a very substantial shaking of the ground or windows.
Bianca: This must be it (Turn to camera) I think we have the answer!
R.J. I wonder what Dr. D would think about this.
Let’s go see him.

DR D’S LAB Kali: I’ll send Dr. Brown an E mail.

R.J. Wow, I didn’t know there really could be sonic booms from meteors.

Bianca: We talked about sonic booms being the answer.
Anthony: But, not sonic booms from a meteor

Kali: We got an e-mail back from Dr. Peter Brown. He says that it probably would take a meteoroid of at least several hundred kilograms, which is the size of a small chair, to produce a sonic boom strong enough to be recorded by a seismograph.
Bianca: Look at this. He also says that if large meteoroid has enough energy and gets deep enough into the atmosphere, it can produce a very substantial shaking of the ground or windows.
Bianca: This must be it (Turn to camera) I think we have the answer!
R.J. I wonder what Dr. D would think about this.
Let’s go see him

(R.J.): Hi, Dr. D. We think we have solved our problem.
DR D: Great. Was it an earthquake?

R.J.: We’re pretty sure that it wasn’t an earthquake. We think that we have proof it was a sonic boom produced by a meteor.
Dr D: A meteor? How did you come to that conclusion?

(Catherine looking at Anthony): It wasn’t easy. Anthony kept insisting it was an earthquake.
I knew it was a sonic boom all along.

Jacob: Not really. We dismissed the sonic boom hypothesis in the beginning because planes don’t generally fly that fast any more over land.

Anthony: Eventually, we came back to the idea of a sonic boom when KSNN reported that a fireball had been seen at the same time the vibrations were felt.

Catherine: When we heard that the people at Virginia Tech saw a fireball, heard a sonic boom, and recorded a seismic reading just a few minutes before we did, it still didn’t register with us that a meteor could be the answer.
Anthony: That’s because it was overcast that day and we didn’t see a fireball.
Jacob: Who would have thought that it would be a fast moving chunk of rock? (Turn to camera) Would you think?Catherine: Then we checked with some experts who told us that meteors can cause sonic booms.
Dr. D: Well, it sounds like you have learned several important things. You’ve learned not to dismiss a hypothesis too quickly as you did with the sonic boom hypothesis.Anthony: Yes, and VA Tech practically gave us the answer, but we didn’t even consider it.
Dr. D: Sometimes the answer is right in front of you, but you can’t always see it. The problem is that you have not completely solved your mystery.
R.J.: We haven’t? What do you mean? We have lots of evidence.
Jacob: We know that it wasn’t a construction blast.
Anthony: We even ruled out an earthquake for a number of reasons.
Catherine: We also eliminated thunder since there weren’t any lightning strikes that day.
Jacob: So Dr. D isn’t the fireball explanation the best one?
Dr. D: Well, to quote the greatest detective of all time, Sherlock Holmes, “Eliminate all other factors, and the one which remains must be the truth."

R.J.: Isn’t that what we did?
Anthony: Well, I guess we also didn’t completely rule out earthquakes..
Dr. D: You have shown that a fireball can cause a sonic boom and that a fireball was seen elsewhere, but you don’t yet have enough evidence to prove that the fireball caused the vibrations that you felt.
Dr. D: In science, you quite often go with the best explanation, even though it is not proven beyond question. Anthony: All who agree that this is the best explanation that we can find say aye.
AYE
Dr. D: Even though you had a lot of dead ends, Along the way, you’ve learned a lot about earthquakes. Sometimes the journey is just as important as the destination.
R.J.: You mean, what we learn along the way is as important as reaching a conclusion.
DR. D: Something like that. Congratulations
Vibration
Jacob: Oh no! It’s happening again!
Anthony: Yes!
(Credit Roll)