the most exciting phrase to hear in science, the one that heralds the most discoveries, is not...
TRANSCRIPT
The most exciting phrase to hear in science, the one that heralds the most discoveries, is not "Eureka!" (I found it!) but "That's funny..." ~Isaac Asimov
The universe is full of magical things patiently waiting for our wits to grow sharper. ~Eden Phillpotts, A Shadow Passes
EARTHQUAKES
WHEN PLATES SLIP, SLIDE, AND COLLIDE.
EARTHQUAKE QUESTIONS
1. NAME THE THREE TYPES OF PLATE BOUNDARIES.
EARTHQUAKE QUESTIONS
1. NAME THE THREE TYPES OF PLATE BOUNDARIES.
DIVERGENT PLATE BOUNDARIES - WHEN PLATES MOVE APART
CONVERGENT PLATE BOUNDARIES - WHEN PLATES MOVE TOGETHER
TRANSFORM PLATE BOUNDARIES - WHEN PLATES MOVE PAST EACH OTHER
EARTHQUAKE QUESTIONS
2. VOLCANOES USUALLY OCCUR ALONG WHAT KINDS OF BOUNDARIES?
EARTHQUAKE QUESTIONS
2. VOLCANOES USUALLY OCCUR ALONG WHAT KINDS OF BOUNDARIES?
CONVERGENT AND DIVERGENT
EARTHQUAKE QUESTIONS
3. EARTHQUAKES USUALLY OCCUR ALONG WHAT KINDS OF BOUNDARIES?
EARTHQUAKE QUESTIONS
3. EARTHQUAKES USUALLY OCCUR ALONG WHAT KINDS OF BOUNDARIES?
CONVERGENT, DIVERGENT, AND TRANSFORM
EARTHQUAKE QUESTIONS
4. THE LARGEST EARTHQUAKE OF THE LAST 100 YEARS OCCURRED ALONG WHICH COAST?
- ASIA- NORTH AMERICA- SOUTH AMERICA
EARTHQUAKE QUESTIONS
4. THE LARGEST EARTHQUAKE OF THE LAST 100 YEARS OCCURRED WHERE?
- SOUTH AMERICA - ALONG THE COAST OF CHILE IN 1960
THIS WAS A 9.2 EARTHQUAKE.
IT ALSO GENERATED A TSUNAMI THAT KILLED 61 PEOPLE IN HAWAII AND HUNDREDS IN JAPAN.
THE SUMATRA-ADAMAN EARTHQUAKE OF 26 DECEMBER 2004 KILLED OVER 230,000 PEOPLE IN 11 COUNTRIES – MOSTLY AS A RESULT OF THE TSUNAMIS THAT WERE GENERATED.
EARTHQUAKE QUESTIONS
5. IF YOU FIND YOURSELF INDOORS DURING AN EARTHQUAKE, IS IT BETTER TO
- RUSH OUTDOORS- STAY INSIDE
EARTHQUAKE QUESTIONS
5. IF YOU FIND YOURSELF INDOORS DURING AN EARTHQUAKE, IS IT BETTER TO
- STAY INSIDE AND TAKE COVER UNDERNEATH SOMETHING STURDY LIKE A DESK. IF YOU RUSH OUTSIDE, YOU MAY BE HIT BY FALLING DEBRIS
EARTHQUAKE QUESTIONS
6. WHICH STATE HAS EXPERIENCED A MAJOR EARTHQUAKE (7.0 OR GREATER) IN THE LAST 200 YEARS?
MISSOURI ALASKACALIFORNIA ARKANSASWASHINGTON IDAHONEVADA MONTANAHAWAII ALL OF THE ABOVE
EARTHQUAKE QUESTIONS
6. WHICH STATE HAS EXPERIENCED A MAJOR EARTHQUAKE (7.0 OR GREATER) IN THE LAST 200 YEARS?
ALL OF THE ABOVE - ALASKA HAS HAD 12
EARTHQUAKE QUESTIONS
7. THE FIRST SEISMIC INSTRUMENTS ACCURATE ENOUGH TO BE USED TO STUDY EARTHQUAKES WERE INVENTED IN WHICH COUNTRY?
-JAPAN-UNITED STATES-ENGLAND-CHINA
EARTHQUAKE QUESTIONS
7. THE FIRST SEISMIC INSTRUMENTS ACCURATE ENOUGH TO BE USED TO STUDY EARTHQUAKES WERE INVENTED IN WHICH COUNTRY?
- JAPAN - BY THREE ENGLISHMEN IN 1880
EARTHQUAKES OCCUR ALONG PLATE BOUNDARIES WHEN THE PLATES STICK RATHER THAN SLIDING PAST EACH OTHER.
PRESSURE BUILDS UP UNTIL IT IS STRONG ENOUGH TO OVERCOME THE FRICTION.
WHEN IT SLIPS, AN EARTHQUAKE OCCURS.
IN THE SAN FRANCISCO EARTHQUAKE OF 1906, IT WAS FOUND THAT ONE SIDE OF THE FAULT SLIPPED 21 FEET COMPARED TO THE OTHER SIDE OF THE FAULT.
WHERE DO EARTHQUAKES OCCUR?
ALONG PLATE BOUNDARIES AND FAULT LINES
The Richter scale is a standard scale used to compare earthquakes. It is a logarithmic scale, meaning that the numbers on the scale measure factors of 10.
So, for example, an earthquake that measures 4.0 on the Richter scale is 10 times larger than one that measures 3.0.
On the Richter scale, anything below 2.0 is undetectable to a normal person and is called a microquake. Microquakes occur constantly.
Moderate earthquakes measure less than 6.0 or so on the Richter scale. Earthquakes measuring more than 6.0 can cause significant damage. The maximum quake rating ever measured is about 9.2.
HOW COMMON ARE EARTHQUAKES?
Magnitude (Richter Scale) Number per Year
0 – 3.4 >800,000
4.9 – 5.4 1400
5.5 – 6.1 500
7.0 – 7.3 15
>8 1 every 10 years
EARTHQUAKES OCCUR UNDER THE SURFACE OF THE EARTH.
THE POINT ON THE SURFACE ABOVE WHERE THE EARTHQUAKE OCCURRED IS CALLED THE EPICENTER. THIS WILL ALSO BE THE PLACE WHERE THE MOST DAMAGE OCCURRED.
THE POINT UNDERGROUND WHERE THE EARTHQUAKE OCCURRED IS CALLED THE FOCUS.
A SEISMOGRAPH CAN BE USED TO LOCATE THE EPICENTER.
THERE ARE TWO KINDS OF PRESSURE WAVES FROM AN EARTHQUAKE – P WAVES AND S WAVES.
A P WAVE IS A COMPRESION WAVE, AND THEY TRAVEL THE FASTEST.
AN S WAVE IS AN UP AND DOWN WAVE, AND THEY TRAVEL THE SLOWEST.
THE DIFFERENCE IN ARIVAL TIMES AT A SEISMPGRAPH STATION CAN BE USED TO DETERMINE HOW FAR AWAY AN EARTHQUAKE IS.
THIS IS AN EXAMPLE OF A SEISMOGRAPH SIGNAL. THE DIFFERENCE IN THE ARRIVAL TIME OF THE P WAVE TO THE ARRIVAL TIME OF THE S WAVE IS 24 SECONDS.
TABLES CAN BE USED TO ESTIMATE DISTANCE.
IF YOU HAVE 3 STATIONS, YOU CAN MEASURE THE DISTANCE FROM THE EPICENTER TO EACH STATION, DRAW CIRCLES FOR THAT DISTANCE AROUND EACH STATION.WHERE THEY INTERSECT WILL BE THE EPICENTER.
MORE ON P WAVES AND S WAVES.
ALTHOUGH P WAVES ARE THE FASTEST, S WAVES ARE MORE DESTRUCTIVE BECAUSE THE SURFACE OF THE EARTH IS MOVING UP AND DOWN.
SECONDARY EFFECTS OF EARTHQUAKES
[It is these phenomena that actually kill people, i.e., ground-shaking does not usually harm an individual (maybe their pants!), it is what the shaking does to the surrounding environment that results in bodily harm!]
-Ground shaking (structural collapse, large fissures, etc.)
-Fires (in urban settings; broken gas lines, etc.)
-Landslides
-Ground liquefaction
-Seismic sea waves (Tsunami’s)
FACTORS EFFECTING THE DESTRUCTIVENESS OF AN EARTHQUAKE
MagnitudeThe more energy released, the greater potential for damage, regardless of all other factors (and greater areal extent).
DistanceShaking decays with distance
Local soils and bedrock geology
Soil characteristics may amplify the shaking.
(seasonal climatic variations can impact this)
Complex geology tends to dampen waves
Building codes and materials