Richter Scale

A logarithmic Richter scale measures energy release during plate movements—an increase of 1 in magnitude corresponds to a 10-fold increase in the amplitude of shaking.

From: Earthquake-Resistant Structures , 2013

Post-Tsunami Engineering Forensics

Ioan Nistor , Dan Palermo , in Handbook of Coastal Disaster Mitigation for Engineers and Planners, 2015

3.2 The 2010 Chilean Tsunami Engineering Forensic Survey

A major 8.8 magnitude (Richter scale) earthquake struck along the Pacific coast of Chile on 27 February 2010. The earthquake focal depth for this event was approximately 30  km and the epicenter was located 95   km NW of the town of Chillán. The seismic rupture had a width of over 100   km and a length of approximately 500   km and was parallel to the Chilean central coastline. The first tsunami wave was observed in Valparaiso 30   min after the earthquake (Dunbar et al., 2010). The largest wave height noted during a field survey by Lagos et al. (2010) was 11.2   m in the town of Constitución, while 8.6   m high waves were measured in Dichato and Tomé. Fritz et al. (2011) noted that the tsunami reached a localized runup of 29   m on a coastal bluff at Constitución. The maximum inundation distance of approximately 1032   m was observed in Playa Purema. While many coastal communities suffered widespread damage, the number of casualties attributed to the tsunami was low (see Chapter 6). According to the International Tsunami Information Center, approximately 124 deaths were attributed to the tsunami. This was a direct result of two factors. First, Chile had experienced a major tsunami in 1960, which remains engrained in the memory of the local population (see Chapter 11). The 1960 event was triggered by a 9.5 magnitude earthquake, and approximately 1000 deaths were directly attributed to the tsunami. The largest wave height was 25   m at Isla Mocha (Dunbar et al., 2010). For the 2010 tsunami, in general, those living along the coast immediately searched for higher ground upon experiencing the ground shaking caused by the earthquake. Second, the central coastline of Chile is in close proximity to higher ground providing a natural vertical evacuation (see also Chapter 11).

The second tsunami field reconnaissance survey was conducted in March 2010 along the central coastline of Chile, following the February 27, 2010 earthquake and tsunami by a multidisciplinary Canadian research team. The team investigated damage caused by both the earthquake and the ensuing tsunami. A reconnaissance team organized under the auspices of the Canadian Association of Earthquake Engineering (Palermo et al., 2013) surveyed the damage induced by the tsunami along a 400   km stretch along the Chilean coastline stretching from Talcahuano in the south to Pichilemu in the north. Figure 4 illustrates typical damage sustained by residential structures that were surveyed during this tsunami field investigation.

Figure 4. Tsunami damage due to the February 2010 Chile Tsunami.

The survey results indicated that robust, modern engineered structures performed well during this tsunami and, generally, damage only to non-structural components, such as glazing units, were evident. The survival of these structures provided an opportunity to establish the depth of inundation at the location of these structures. The majority of damage was sustained by non-engineered residential homes located within the inundation zone near the coastline. These dwellings were, for the most part, either light timber frame construction or concrete frame construction with brick masonry infill walls. It was not uncommon for many of the dwelling structures to incorporate sheet metal as exterior cladding or roofing. The hydrodynamic (drag) forces, impulsive loading from the leading edge of the inland advancing tsunami, hydrostatic forces, and debris impact loading, were the probable mechanisms during the tsunami that caused the observed damage. Failures included punching of brick masonry infill walls, partial and complete collapse of load bearing elements such as columns, and sliding and unseating failures of second storey levels and roofs. Critical infrastructure, such as roads and reinforced concrete hydro poles were also heavily damaged and in many cases failed. Small debris impacts caused by timber from collapsed dwellings and large debris impact in the form of automobiles, fishing vessels, and shipping containers were widespread. This reconnaissance investigation provided evidence that the location of a structure dictates the type of debris to consider in design. At a minimum, timber debris should be considered. Structures located near ports should take into account debris impact from shipping containers, while structures situated in fishing communities should consider the effects of fishing vessels.

Although damage was extensive in the coastal communities, an interesting observation made during the reconnaissance trip was that emergency preparedness was very evident in the form of tsunami evacuation route signs and tsunami warning signs. Interviews with local residents revealed that the population was well educated regarding tsunami evacuation procedures. This was a major contributing factor for the low number of casualties (See also Chapter 11).

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128010600000204

Natural disasters and earth buildings: resistant design and construction

H.W. Morris , in Modern Earth Buildings, 2012

Earthquake magnitude

Magnitude is best known from the historic Richter Scale which gives local magnitude, M or M L, and is widely reported after earthquakes. It correlates with the amount of energy released at the hypocentre for medium-sized local events. (It is important to note that this scientific measure of magnitude may not relate to damage or felt intensity due to distance, depth and other factors.) The moment magnitude scale (Mw) is more recent than the Richter Scale and is directly related to the size of the rupture surface and length, and is a much more accurate measure of energy release for events greater than Mw 6.5. These scales of magnitude are logarithmic; the energy content increases by a factor of 32 with each complete integer on the scale as shown in Fig. 19.12.

19.12. The relative size of earthquakes at the focus, a magnitude 7 event releases 32 times the energy of a magnitude 6 on the Richter scale or the moment magnitude scale.

One magnitude 8 earthquake releases around one million times the energy of a frequently felt magnitude 4 earthquake. In the last 20   years there has been an annual average worldwide of about 140 earthquakes of magnitude 6–6.9, 14 of magnitude 7–7.9 and one of magnitude 8 or greater.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780857090263500198

Modern Earthquake Engineering

Mohiuddin Ali Khan Ph.D., P.E., C. Eng., M.I.C.E. (London) , in Earthquake-Resistant Structures, 2013

1.7 Seismic Instrumentation

The number of earthquakes being reported is greater than in the past (see Table 1.2) primarily because of increased concern and the development of modern instrumentation. The USGS National Earthquake Information Center (NEIC) receives data in real time from nearly 990 stations in 85 countries, including the 150-station Global Seismographic Network, which is jointly supported by USGS and the National Science Foundation (NSF) and operated by USGS in partnership with a consortium of universities known as Incorporated Research Institutions for Seismology (IRIS).

Modern seismic instrumentation such as seismogram, seismograph and seismoscope (described below) uses complex electronics to accurately record ground shaking. Electronics have given rise to high-precision pendulum seismometers and sensors of both weak and strong ground motion. Electronic voltages produced by the motions of a pendulum are passed through electronic circuitry to amplify the ground motion and digitize the signals for more exact measurements.

Seismograms

A seismogram shows the amplitude of body and surface waves, which indicates the amount of strain energy released. Richter magnitude is measured in energy (ergs): M=log10 (A/A0), where A=amplitude on a seismograph, and A0=1/1,000 millimeters. Each increase of 1 in Richter magnitude represents a 31-fold increase in the amount of released energy. Thus, a magnitude of scale-6 intensity=10×a magnitude of scale-5 intensity.

The amount of energy released by an earthquake is related to the Richter scale by the equation log E=11.8+1.5M, where

log=logarithm to the base 10

E=energy released, in ergs

M=Richter magnitude.

Seismographs

A seismograph records ground motions such as accelerations and displacements as a function of time using the principle of inertia. The record of ground shaking helps locate the quake's epicenter and focus. Special arrays of strong-motion seismographs have been installed in areas of high seismicity around the world, both away from and on structures. Strategically placed on structures, they provide information on structural response.

Earthquakes can be recorded up to great distances because seismic waves travel through the Earth's interior. When a vibration reaches the seismograph, the movement of the earth in relation to a stationary mass is recorded. The equivalent energy released can be comparable to that of an atomic bomb. For example, the atomic bomb dropped on Hiroshima released an amount of energy equivalent to a quake of magnitude 5.5.

Seismoscopes

Seismoscopes, usually arrayed in networks, indicate the occurrence of an earthquake. With increases in seismic literacy, the size of seismoscopic networks has increased from about 350 stations in 1931 to many thousands today. The first seismoscope was invented by the Chinese philosopher Chang Heng in 132 A.D.

Shake Maps

Correlations have been worked out between measured characteristics of seismic waves and reported Modified Mercalli intensity. A common correlation is that between the maximum ("peak") ground acceleration, A, and the MM intensity, I. Peak ground acceleration (PGA) is employed in the current USGS Shake-Maps program, which produces maps showing ground-shaking intensities that are made available online within a few minutes of an event. The geographical distribution of intensity is summarized by constructing isoseismal curves, or contour lines, that separate areas of equal intensity.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9781856175012000018

Introduction

Zihai Shi , ... Hajime Kubo , in Structural Resilience in Sewer Reconstruction, 2018

1.2.1 Fukushima Daiichi nuclear accident

On March, 11, 2011, an earthquake measuring nine on the Richter scale struck near the east coast of Honshu, Japan. The Great East Japan Earthquake was caused by multisegment failures of the Earth's crust over wide areas in the nearby Japan Trench. It was the most powerful earthquake ever recorded in Japan, and triggered powerful tsunami waves which struck a long area of the coast, including the north-eastern coast, where several waves reached heights of more than 10  m. The earthquake and tsunami caused great loss of life and widespread devastation: more than 15,000 people were killed, over 6000 were injured, and around 2500 people were still reported missing 4 years after the event (IAEA, 2015). Considerable damage was caused to buildings and infrastructure, particularly along Japan's north-eastern coast.

At the Fukushima Daiichi nuclear power plant, operated by Tokyo Electric Power Company (TEPCO), the earthquake damaged the electric lines supplying power to the site, and the subsequent tsunami caused substantial damage to the operational and safety infrastructure on the site. All on-site and off-site power was completely lost, but most importantly, flooding of the electric equipment room cut the supply of electricity to components and devices. This resulted in the failure of the cooling systems in the three operating reactor units as well as the spent fuel pools.

Despite the efforts of the reactor operators to maintain control, the reactor cores in Units 1, 2, and 3 overheated, the nuclear fuel melted, and the three containment vessels were breached. Hydrogen was released from the reactor pressure vessels, leading to explosions inside the reactor buildings in Units 1, 3, and 4 that damaged structures and equipment and injured personnel. Radionuclides were released into the atmosphere and then deposited onto the land and ocean. There were also direct releases into the sea. People within a radius of 20   km of the site and in other designated areas were evacuated, and those within a radius of 20–30   km were instructed to take shelter before later being advised to voluntarily evacuate. The Fukushima Daiichi nuclear accident, which was rated Level 7 on the International Nuclear and Radiological Event Scale (INES) by the Japanese government's nuclear safety agency, was the worst accident at a nuclear power plant since the first Level-7 major disaster at Chernobyl in 1986.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128115527000018

Examples of Risks Having the Potential for Catastrophic Consequences

B. John Garrick , in Quantifying and Controlling Catastrophic Risks, 2008

7.12 Super Earthquakes

What is a super earthquake? The most common measure of earthquake strength is the Richter scale, which measures the "moment magnitude" and describes horizontal movement. It is a logarithmic scale. A magnitude 6 earthquake has ten times more energy intensity or movement than a magnitude 5 on the Richter scale. The Richter scale has its limitations, as it does not reflect the impact of vertical movement, which can be the wave movement causing the greatest amount of damage. However, for most earthquakes the Richter scale has provided reasonably well correlation with the resulting damage. Other measures of earthquakes could be number of fatalities or injuries, the peak value of the shaking intensity, or the area of intense shaking. As to a formal definition of a super earthquake, there does not appear to be one. So we will loosely take a super earthquake to mean one that has a Richter value of 8 or more or results in thousands of fatalities or billions of dollars of property loss and damage. This is in keeping with the theme of this book to target high consequence, low probability events. a

History would suggest that earthquakes have been one of the more serious risks to societies. The U.S. Geological Survey has cataloged the ten most deadly earthquakes since the 9th century. The number of fatalities is staggering and varies from 830,000 in Shansi, China, in 1556 to 100,000 in Messina, Italy, in 1908. The most recent on this top ten list occurred in Tangshan, China, in 1976 and killed 242,000 people. The total number of fatalities for the ten is a staggering 4,810,000. Of course, this is just the top ten over that period, not the total earthquake fatalities, which has to be a much larger number. Four of the top ten were in China, two in Iran, and the rest were in Syria, Japan, Turkmenistan, and Italy. None were in the Americas. While the magnitudes of many of these earthquakes were not known from direct measurements, as there was no such capability to do so for most of them, earthquake experts have been able to reconstruct estimates by analyzing the descriptions of the damage incurred.

Earthquake damage (fatalities and property damage), like hurricane damage, is strongly dependent on where it occurs, the resistance of buildings and services to damage, and emergency preparedness. For example, the earthquake that took place in Bam, Iran, on December 26, 2003, having a magnitude of 6.6, resulted in killing over 26,000 people, injuring 20,000, leaving 60,000 homeless, and destroying most of the city. Meanwhile, a similar magnitude earthquake, which took place in central California about the same time, did not cause any dramatic damage or loss of life. It has been estimated that half of the 6 million people in the capital cities of the five central Asian republics occupy buildings that are extremely vulnerable to collapse during earthquakes with death tolls up to 135,000 people and at least 500,000 injuries. The difference appears to be in the vulnerability of structures and infrastructure; in California they were ready for such earthquakes and in Bam, Iran, and apparently many other places, they were not. The good news is there is strong evidence that it is possible to greatly reduce the risk of super earthquakes with better information on where they are likely to occur, better building codes, improvements in design and construction of housing and facilities, emergency preparedness, and greater government involvement.

Perhaps the greatest risk of earthquakes, given the increased ability to lessen their impact, is not the earthquake itself, but its ability to trigger other catastrophic events such as volcano eruptions, landslides, and tsunamis. A case in point is the 9.0 earthquake in the Indian Ocean near Sumatra on December 26, 2004, that created a tsunami resulting in almost 300,000 people dead and thousands missing. This same earthquake is believed to have resulted in a flurry of events in the Mount Wrangell volcano in Alaska 7000 miles away. The 7.9 Denali Fault earthquake in 2002 triggered similar volcanic activity at Yellowstone and northern Mexico. Fortunately, neither of the flurry of events resulted in any serious damage to property or life.

Methods for quantifying the risk of earthquakes have greatly advanced primarily because of the need to quantify their occurrence at nuclear facility sites. There is great opportunity for the risk sciences to reduce the risk of earthquakes as triggering events for tsunamis and volcano eruptions.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780123746016000078

Case study

A. Pipinato , in Innovative Bridge Design Handbook, 2016

2.4 Seismic devices

The Russky Bridge could experience an earthquake with a magnitude of up to 8.1 on the Richter scale. This represents a safety margin comparable to the very high requirements of other bridges (e.g., the Akashi Kaikyo Bridge's resistance is 8.5). The designed system of two-hinged stiffening girders was conceived in order to allow seismic loads up to 8.1 points, along with strong sea currents. Pendulum-type bearing structures were introduced to reduce the active loads, ensuring the seismic isolation of the span deck. Movement joints have endured large axial displacements of the span deck, and lead-cored rubberized metal bearings have been adopted to dissipate energy under large stresses.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128000588000256

Nuclear Energy

Brian F. Towler , in The Future of Energy, 2014

The Fukushima-Daiichi Incident

The Fukushima-Daiichi nuclear incident was caused by a huge earthquake (9.0 on the Richter scale) off the northeast coast of the main Japanese Island of Honshu on March 11, 2011. The earthquake spawned a giant tsunami that created waves up to 128  ft tall in some areas adjacent to the earthquake. The waves were estimated at 45   ft tall when it swamped the Fukushima-Daiichi nuclear power plant, 120 miles away, about 1   h after the earthquake. The power plant is on the northeast coast of Honshu island about 120 miles southwest of the epicenter of the earthquake, which was located about 80 miles offshore from the city of Sendai.

There are 6 reactors at the Fukushima-Daiichi nuclear power plant, but at the time of the quake, reactors 4, 5 and 6 had been shut down for maintenance. Reactors 1, 2 and 3 were operating, but they shut down automatically after the earthquake, with emergency electrical generators starting up to run the water pumps needed to cool the reactor cores. The plant was protected by a seawall designed to withstand a 19-ft tsunami, but when the 45-ft wave arrived the entire plant was flooded, knocking out the generators and the cooling water pumps. This caused a partial core meltdown in the operating reactors 1, 2 and 3. Explosions and severe damage occurred, and radiation leaked out into the surrounding countryside. The entire area, which had been badly damaged by the earthquake and tsunami, had to be evacuated to within 30   km of the plant. Figure 7.9 shows the cumulative radiation contamination as of April 29, 2011. No deaths or severe illnesses can be attributed to the accident, but the incident is ongoing at the time of publication.

Figure 7.9. Map of deposition of Radio-Cesium (sum of Cs-134 and Cs-137) for the land area Within 80   km of the Fukushima-Daiichi Plant, as reported by the Japanese Authorities.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128010273000075

Fukushima: The current situation and future plans

O. Farid , ... H. Yamana , in Radioactive Waste Management and Contaminated Site Clean-Up, 2013

24.1.2 Tsunami damage to the reactors

The sequences of events in the reactor accident were as follows:

1.

Fukushima was shaken by an earthquake measuring magnitude 9.0 on the Richter scale; however, the six NPPs were designed on the basis of an earthquake equivalent to magnitude 8.2.

2.

The three units in operation, units 1, 2 and 3, automatically went into SCRAM (sudden shutting down of a nuclear reactor, usually by rapid insertion of control rods), which was triggered by detecting the high earthquake acceleration. Following the total loss of off-site power, emergency power generators automatically started to supply electricity.

3.

The standard post-shutdown cooling modes started up to remove the decay heat. This residual heat must be removed to prevent the nuclear fuel, mainly UO2, cladding metal, and supporting structural elements from melting in the core of the reactor. The melting point of UO2 is approximately 2,900   °C, while those of cladding and supporting parts are in the range of 1,300–1800   °C.

4.

About 45   minutes after the earthquake, tsunami waves variously hit the units, destroying seawater pumps for the residual heat removal system and many of the emergency generators. Eventually, this lead to the total loss of the electricity that powered the water pumps used to maintain cooling water circulation around the reactor cores. The spent fuel (SF) storage pools suffered the same problem.

5.

In spite of the performance of various emergency core cooling systems, as well as trials to vent the reactor vessel enabling water injection from outside, the core eventually became uncovered by cooling water. Along with the increase in temperature of the uncovered fuel, the reaction of cladding material with steam to generate hydrogen proceeded rapidly, and the fuel started melting leading to core destruction through meltdown.

6.

According to the results of the simulation calculation conducted even with insufficient records of the instrumentation, most of the core is believed to have melted in unit 1. In units 2 and 3, much of the fuel apparently melted but to a lesser extent than in unit 1 and dropped to the bottom of the pressure vessel. It is considered that a certain part of the fused fuels and structural materials flowed out from the reactor pressure vessels (RPVs) into the primary containment vessels (PCVs).

7.

During the severe accident process, appreciable amounts of volatile radionuclides (typically these are noble gases, cesium and iodine) are considered to have evaporated. They must have escaped from the RPV into the PCVs, and finally escaped via cracks or openings made under the severe conditions.

8.

Hydrogen explosions occurred in units 1, 3 and 4, and these seriously damaged their operation floors at the top of the reactor building, and also the upper side walls of unit 4.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780857094353500240

Reconstruction of Informality

Mojgan Taheri Tafti , in Urban Planning for Disaster Recovery, 2017

Bam Earthquake and Reconstruction

Two years after the Bhuj earthquake, on December 26, 2003, the historic city of Bam (Fig. 8.2 ) in Iran was affected by an earthquake registering 6.6 on the Richter scale. With a population of 104,469, Bam lost 23,503 people—almost one-fourth of its population. More than 80% of buildings in the city and around 24,598 urban housing units were severely damaged ( World Bank, 2010). Before the earthquake, around 18.8% of the people were renters (Ghafory-Ashtiany & Mousavi, 2005).

Figure 8.2. Location of Bam in Iran.

Postearthquake policy responses were formulated by the central government. Financing the recovery program relied primarily on public funds and a US $220   million loan from the World Bank. The new development plan of Bam suggested an in situ reconstruction for the city. Unlike the recovery programs in Bhuj, which focused on economic growth, in Bam the economic recovery of the city was almost totally overlooked (World Bank, 2010), and officials narrowly interpreted recovery as the reconstruction of damaged buildings. Like Bhuj, policies of assistance distribution to households were mainly concerned with housing reconstruction for homeowners. According to these policies, property owners were eligible to receive a maximum of US $17,647 for building an 80   m2 house, for each damaged house they owned. Two years after the earthquake, renters—in addition to new couples—became eligible for receiving a grant, provided that they bought a plot or could build a second unit in their extended household's plot.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128042762000086

Safety in Rock Engineering

Zong-Xian Zhang , in Rock Fracture and Blasting, 2016

23.3.4 Consequence of Seismic Events

A strong seismic event may cause spalling, rock fall, and collapse in underground structures such as production drifts. For example, a seismic event that happened at a place 1100 m below the ground surface in the Kiruna mine reached 2.1 on the Richter scale. This event resulted in a total of 170 m 3 rock fall; most of the rock fall appeared on the level at 1045 m below the surface and less on levels at 1020 m and 964 m. Figs. 23.12 and 23.13 show the rock fall on levels at 1045 m and 1020 m, respectively.

Figure 23.12. Spalling and rock fall on level 1045 m due to a seismic event.

Figure 23.13. Spalling and rock fall on level 1020 m due to a seismic event.

A seismic event can also give rise to rock mass damage in a mine because the stress field is suddenly changed. For the production blastholes that are particularly empty, a large deformation may be caused due to the seismic event. As a result, some blastholes may be broken or seriously deformed. This is one of the reasons that many blastholes in sublevel rings fail to charge either partly or wholly. This problem has been discussed in the chapter: Rock Blasting in Underground Mining.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128026885000233