The Handy Geography Answer Book. Paul A Tucci

In a few million years, the two cities will be neighbors.

      Was San Francisco destroyed by earthquake or by fire in 1906?

      In 1906, a very powerful earthquake struck San Francisco, California, which sparked a fire that destroyed much of the city. In an effort to preserve San Francisco’s image with residents and would-be visitors, official policy regarding the disaster stated that it was not the earthquake but mostly the fire that destroyed the city. Official books and publications produced after the earthquake referred to both the fire and the earthquake as having caused the damage. In fact, the earthquake did considerable damage to the city and killed hundreds.

       Will California eventually fall into the ocean?

      No, it will not. The famous San Andreas Fault, which runs along the western edge of California from the San Francisco Bay area to southern California, is known as a transverse fault. This means that the western side of the fault, which includes places like Monterey, Santa Barbara, and Los Angeles, is sliding northward with respect to the rest of the state. In a few million years, the state’s two largest urban areas, San Francisco and Los Angeles, will be right next to each other. The fault is moving at about two centimeters (just under an inch) a year.

      A view of San Francisco taken from the Union Ferry Building and looking toward Market street shortly after the 1906 earthquake and fire.

      Which states are earthquake-free?

      While a twenty-year period isn’t an excellent indicator, there are four states that had no earthquakes between 1975 and 1995: Florida, Iowa, North Dakota, and Wisconsin.

      Is there a high risk of earthquakes in the Midwestern United States?

      Great earthquakes struck the New Madrid, Missouri, area in 1811 and 1812. They caused considerable damage (some areas experienced shaking at the level of XI on the Mercalli scale) and were felt as far away as the East Coast. The potential exists for future earthquakes in the region, since earthquakes have occurred there before. Planning and preparedness continues throughout the region, centered at the junction of Missouri, Arkansas, Illinois, Kentucky, Tennessee, and Mississippi.

      What should I do in the event of an earthquake?

      Duck, cover, and hold! Duck under a table, counter, or any area that can provide protection from falling objects. Cover the back of your head with your hands to help protect against flying debris. Hold on to the leg of the table or anything solid to ride out the shaking.

      Is it safe to stand in a doorway during an earthquake?

      While a doorway is a nice, structurally sound place to be during an earthquake, officials have found that many people are injured when a door swings open and closed during an earthquake, so you may want to avoid standing in a place where your fingers can become crushed.

      What is the Richter scale?

      The Richter scale measures the energy released by an earthquake. It was developed in 1935 by California seismologist Charles F. Richter. With each increase in Richter magnitude, there is an increase of thirty times the energy released by an earthquake. For example, a 7.0 earthquake has thirty times the power of a 6.0 earthquake. Each earthquake only has one Richter magnitude. The strongest earthquakes are in the 8.0–9.0 range—8.6 for Alaska’s 1964 earthquake and 8.0 for China’s 1976 earthquake in Tangshan.

      What is the Mercalli scale?

      The Mercalli scale measures the power of an earthquake as felt by humans and structures. Italian geologist Giuseppe Mercalli developed it in 1902. The Mercalli scale is written in Roman numerals, and it ranges from I (barely felt) to XII (catastrophic). The Mercalli scale can be mapped surrounding an epicenter and will vary based on the geology of an area.

       The Mercalli Scale of Earthquake Intensity

      What does an earthquake feel like?

      Smaller earthquakes or tremors feel disorienting at first. You feel a sense that the room is spinning, as if you are becoming dizzy. Usually preceding an earthquake, when the initial tremors hit, you can hear the sounds of things rattling that you have never heard before, like glasses rubbing against each other and windows vibrating. With larger earthquakes, as the earth nearby tears or opens, you can hear a very loud rumbling sound that is similar to a passing train.

      How many mini-earthquakes happen each year on our planet?

      Experts at the U.S. Geological Survey believe that if we consider earthquakes of low magnitudes of between 2 and 2.9, there are an estimated 1.3 million mini-earthquakes each year, somewhere on Earth.

      How many really big earthquakes occur each year?

      On average, there are about 134 earthquakes of a magnitude 6.0–6.9, about fifteen of a magnitude 7.0–7.9, and one huge magnitude 8.0–8.9 earthquake each year. Many of these really big earthquakes occur in the ocean, so we don’t hear much about them.

      Is a magnitude ten the top of the Richter scale?

      While the media often refers to the Richter scale as being on a scale of one to ten, there is no upper limit, even though the strongest quakes are not as high as ten.

TSUNAMIS

      What causes a tsunami?

      A tsunami, also known as a seismic sea wave, is usually caused by an earthquake that occurs under the ocean or near the coast of a landmass. The seismic energy creates a large sea wave that can cause heavy damage hundreds or even thousands of miles from its source. The state of Hawaii is frequently struck by tsunamis.

      How does Hawaii protect itself from tsunamis?

      There is a sophisticated global monitoring network that provides warnings about possible tsunamis, allowing the islands of Hawaii and other coastal areas to prepare for impending disaster. Hawaii also has a thorough evacuation system to protect lives in the face of tsunami danger.

      What caused the great Indian Ocean tsunami of December 2004?

      The great Indian Ocean tsunami of December 2004 was caused by a magnitude 9.0 earthquake in the ocean off the coast of Sumatra, Indonesia, which then caused a reverberating swell of water to move toward the countries of Indonesia, Thailand, Sri Lanka, India, and the Maldives. Its effects were felt as far away as Africa before its energy finally dissipated.

      What was the effect of the 2011 Tohoku earthquake and tsunami that occurred in Japan?

      The magnitude 9.0 earthquake that occurred off the coast of Japan in March 2011 caused a tsunami, which melted down three nuclear reactors at the Fukushima Daiichi Nuclear Power Plant. Approximately 16,000 people lost their lives, and many millions of people were without electricity and water for several weeks after the incident.

      What is the Pacific Tsunami Warning Center?

      The United States has two tsunami warning centers that are administered by the National Oceanic and Atmospheric Administration: the Pacific Tsunami Warning Center based in Hawaii and the West Coast and Alaska Tsunami Warning Center. The Pacific Tsunami Warning Center is the command center for monitoring and warning all nations that may be affected by a tsunami. With data from a network of thirty-nine detection buoys called the DART array, the center can issue alerts of real-time earthquake activity in the Pacific basin and the tsunamis that may result, giving residents affected time to head to safe ground, away from low-lying coastal areas.

      What is the DART array?

      DART stands for the Deep-Ocean Assessment and Reporting of Tsunamis, which consists of an array of thirty-nine buoys that float in critical spots in the Pacific. Each DART system consists of an anchored seafloor bottom-pressure recorder (BPR) and a companion moored surface buoy for real-time communications. An acoustic link transmits data from the BPR on