A-seismograph works by transferring movements of the earth to a graph. (See illustration below.)-↓ ↓ frame transmits Earth's vibrations to wire frame- wire heavy weight rotating paper drum. pen seismogram tracing of vibrations horizontal Earth movements ↓ base set into the ground In-1935-Charles-F. Richter of Cal-Tech developed a-scale for measuring the magnitude of earthquakes. The Richter Scale formula-is-given-hye E MR = 108 10 E where M* is the Richter magnitude of the earthquake. E joules is the energy released-by-the- earthquake, and E =10** joules is the reference energy of a very small, imperceptible- earthquake. (See plot-below.)< a) When the energy of an earthquake is tripled, by how much does the Richter magnitude- increase? b)→In 1906, the San Francisco Bay area suffered severe damage from an earthquake estimated-to- have had a magnitude of 8.3. The largest earthquake magnitude ever measured was 8.9 for an earthquake-in-Japan-in-1933. Determine the ratio of the energy of this earthquake to that of the 1906 San Francisco earthquake.< SEISMIC EVENT ENERGY RELEASE (JOULES) 2,000,000,000,000,000,000- Seismic Event Frequency & Impact 63,000,000,000,000,000- 2,000,000,000,000,000- 9.0 Magnitude Impact 9-9.9 8-8.9 7-7.9 6-6.9 5-5.9 4-4.9 3-3.9 2-2.9 <2 Catastrophic: can cause irreparable damage and immense loss of life Great: can cause severe damage and loss of life Major: can cause serious damage over large areas Strong: can be destructive in populated areas Moderate: can cause damage to poorly constructed buildings over small regions Light: noticable shaking but significant damage is unlikely Small: often felt but rarely causes damage Minor: easily recorded at surface but not felt Micro: not felt at surface, causes no damage and can only be measured deep underground Global Frequency 2011 Japan Earthquake 1 a decade 1 per year 1 per month 2 a week 4 per day 1 per hour 15 per hour 2 per minute continual GREAT 8.0 63,000,000,000,000- 2,000,000,000,000- 63,000,000,000- 2,000,000,000- 63,000,000 Vibrations felt by a passing truck 5.0 4.0 2.0 3.0 1.0 0 -1 2,000,000- 63,000 Typical microseismic events during hydraulic fracturing are -2 2 3 6.0 MAJOR 7.0 STRONG MODERATE LIGHT SMALL MINOR NOT FELT/MICRO 5 7 8 MAGNITUDE* ON RICHTER SCALE Source: USGS