Tuesday, January 19, 2010

What Does the Richter Scale Really Mean?

What Does the Richter Scale Really Mean?

Earthquakes are measured using the Richter Scale. Here's a breakdown of what the numbers really mean:

Less than 2.0: Micro
Microearthquakes, not felt.
About 8,000 per day

2.0-2.9: Very minor
Generally not felt, but recorded.
About 1,000 per day

3.0-3.9: Minor
Often felt, but rarely causes damage.
49,000 per year (est.)

4.0-4.9: Light
Noticeable shaking of indoor items, rattling noises. Significant damage unlikely.
6,200 per year (est.)

5.0-5.9: Moderate
Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings.
800 per year

6.0-6.9: Strong
Can be destructive in areas up to about 100 miles across in populated areas.
120 per year

7.0-7.9: Major
Can cause serious damage over larger areas.
18 per year

8.0-8.9: Great
Can cause serious damage in areas several hundred miles across.
1 per year

9.0 or greater: Rare, Very Great
Devastating in areas several thousand miles across.
1 per 20 years

12.0:
Would be strong enough to split the earth in half.

When (Not If, When) Will the Big Earthquake Hit the Midwest?

When the next "big one" will hit is the million-dollar question among earthquake enthusiasts. But perhaps an even more appropriate question isn't when the next big one will hit, but where.

Though California is often regarded as the earthquake epicenter of the nation, there is another major fault line that most people are not aware of. It runs right through the heart of the "American breadbasket," and when it has its (next) big break, experts say the impact could be far worse than anything the West Coast has experienced in modern times.

Comparable earthquakes in the New Madrid Zone and the West Coast. Red indicates area of structural damage, yellow indicates area where shaking was felt.

The New Madrid Fault System spans a 120-mile stretch from Charleston, Missouri and Cairo, Illinois, down Interstate 55 to end up in Marked Tree, Arkansas. The massive zone crosses five state lines and cuts across the Mississippi River in three places and the Ohio River in two.

It's true that the greatest risk of earthquakes in the United States is definitely along the West Coast ... but, although the tremors may not be as frequent, when they do occur along the New Madrid Fault Line, the damage covers more than 20 times the area.

When Will the Next "Big One" Hit the Midwest?

We say the "next" big one because a major earthquake event did hit this region in the past. The Great New Madrid Earthquake of 1811-1812 describes a series of over 2,000 shocks that spanned a five-month period, destroying farmland and causing great destruction.

Although the Richter Magnitude Scale that we use to measure earthquakes today wasn't available at this time, it's estimated that five of these "shocks" measured 8.0 or higher, and it's said that 18 were strong enough to ring church bells all the way on the East Coast.

The New Madrid Fault Zone is currently active, and has more than 200 measured shocks (over 1.0 on the Richter scale) each year. The St. Charles County (Missouri) Division of Emergency Management (EMD) reports the following activity in the zone:

  • Tremors large enough to be felt (2.5 - 3.0 on the Richter scale) are noted annually.

  • Every 18 months, the fault releases a shock of 4.0 or more, capable of local minor damage.

  • A shock of 4.3 occurred along the New Madrid Fault on Thanksgiving 1996, which was felt by people in the states of Missouri, Arkansas, Tennessee, Kentucky, Illinois and Mississippi.

  • A magnitude of 5.0 or greater, occurring about once per decade, can do significant damage, and be felt in several states.

Further, a damaging earthquake (6.0 or greater) occurs about once every 80 years, the last one being in 1895. This, says the EMD, would cause serious damage to buildings from Memphis to St. Louis.

A major earthquake (7.5 or greater) happens once every 200-300 years, with the last one in 1812. According to EMD, there is a 25 percent chance of an earthquake of this magnitude occurring along the New Madrid Fault Line by 2040.

A quake this size, they say, " ... would be felt throughout half the United States and damage 20 states or more. Missouri alone could anticipate losses of at least $6 billion from such an event."

What Does the Richter Scale Really Mean?

Earthquakes are measured using the Richter Scale. Here's a breakdown of what the numbers really mean:

Less than 2.0: Micro
Microearthquakes, not felt.
About 8,000 per day

2.0-2.9: Very minor
Generally not felt, but recorded.
About 1,000 per day

3.0-3.9: Minor
Often felt, but rarely causes damage.
49,000 per year (est.)

4.0-4.9: Light
Noticeable shaking of indoor items, rattling noises. Significant damage unlikely.
6,200 per year (est.)

5.0-5.9: Moderate
Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings.
800 per year

6.0-6.9: Strong
Can be destructive in areas up to about 100 miles across in populated areas.
120 per year

7.0-7.9: Major
Can cause serious damage over larger areas.
18 per year

8.0-8.9: Great
Can cause serious damage in areas several hundred miles across.
1 per year

9.0 or greater: Rare, Very Great
Devastating in areas several thousand miles across.
1 per 20 years

12.0:
Would be strong enough to split the earth in half.

How about another event like the series of quakes felt in 1811-1812?

Researchers predict that these types of events occur only once every 500-600 years, which means they don't expect another for 100 years or more. However, experts including emergency planners, engineers and seismologists have given the event a 3 percent chance of occurring by the year 2040.

Can Earthquakes Really be Predicted?

While no one can predict an earthquake with utmost certainty, scientists do "forecast" future earthquakes using the best methods currently available.

According to the U.S. Geological Survey (USGS) and the Center for Earthquake Research and Information of the University of Memphis, it's estimated that in the next 50 years along the New Madrid Fault Zone:

  • There's a 7 percent to 10 percent chance of a magnitude 7.5-8.0 earthquake occurring in this region.

  • There's a 25 percent to 40 percent chance of a magnitude 6.0 or larger earthquake occurring.

The EMD has given it an even greater chance, saying there's a 90 percent chance that a 6.0 earthquake will be felt in this region by the year 2040. They say it's events of this size (6.0-7.6) that concern them the most, since they are the ones most likely to occur within the lifetimes of our children, and have the potential to cause great damage.

Joan Gomberg, of the U.S. Geological Survey earthquake hazard program in Memphis, agreed. "If a major earthquake were to hit southern Illinois, the damage could be great," she said. "If it's a six, it depends upon where it hits. If it hits next to an urban area, it could do a lot of damage. But if it occurs in the boondocks, it won't be nearly as damaging."

If an Earthquake Hits the Midwest ... Are They Prepared?

According to an investigation by the St. Louis Post-Dispatch, "Repeated recommendations from all levels of government in an eight-state region of the central United States have been largely ignored on how to best brace for an event that scientists expect will kill thousands and cause widespread chaos."

"We are entirely unprepared," said Amr Elnashai, who runs the Mid-America Earthquake Center at the University of Illinois. "It is really amazing -- really amazing. How can a country as rich and prosperous as the U.S. leave itself in peril this way?"

The Post-Dispatch investigation, in a review of studies and reports and interviews with more than 150 government officials, researchers and preparedness advocates, found:

  • Many government agencies haven't estimated what kind of damage a major earthquake will cause to their emergency facilities, which could cripple response efforts.

  • No plan is in place to renovate older schools to more up-to-date, stricter building codes or even to use low-cost fixes to strengthen them.

  • Utilities are not required to report on hazardous material spills and other problems that could occur during an earthquake, nor their plans to remedy them.

  • Key bridges are vulnerable to earthquake damage, and some states have no programs in place to fix them.

  • Over 80 percent of counties across the region are late to file required plans on how they will prepare for earthquakes and other natural disasters.

  • Some communities haven't held earthquake drills in more than a decade.

However, some progress is being made. Government research has identified key danger zones and risks of earthquakes, and, with all of the terrorism response training in recent years, earthquake response will also improve. Further, some areas have received grants to strengthen vulnerable facilities.

Further, according to the Post-Dispatch, the Federal Emergency Management Agency (FEMA) is planning a comprehensive New Madrid earthquake drill, which hasn't been done since the early 1990s, in 2007. This drill is so important that only one other drill, conducted last year, received higher priority: A drill for a hurricane hitting New Orleans.

Big One sure to come; question is when, are we prepared?

Big One sure to come; question is when, are we prepared?

The 7.0-magnitude earthquake that struck Haiti a few days ago can happen in Metro Manila, according to seismologists and geologists.

The question is: Are we prepared?

It appears that we are not. Experts said preparations should begin in earnest to minimize damage to be caused by the big one.

Director Renato Solidum of the Philippine Institute of Volcanology and Seismology (Phivolcs) said “a strong earthquake can happen” in Metro Manila or anywhere in the country.

He noted that a 7.8-magnitude earthquake struck Luzon in 1990 and a 7.1-magnitude quake shook Mindoro in 1994. “It can happen again,” Solidum said.

Ismael Narag, officer in charge of the Phivolcs seismology department, also said a 7.0-magnitude earthquake hitting Metro Manila was possible because it is transected by the West Valley Fault.

“So a movement of the fault causing a 7.0-magnitude earthquake is realistic,” he said.

Both Solidum and Narag referred to the Metro Manila Earthquake Impact Reduction Study (MMEIRS) conducted by the Japan International Cooperation Agency (JICA).

Phivolcs said the West Valley Fault, located in the Marikina Valley, could generate a 7.2-magnitude quake.

Extensive damage

A 7.2-magnitude quake could damage 38 percent of residential buildings, 38 percent of buildings between 10 and 30 stories, 14 percent of buildings between 30 and 60 stories, and 30 to 35 percent of all public buildings.

The study also said the earthquake could cause 33,500 deaths, an additional 18,000 deaths from fire, and 114,000 injuries.

In addition, the temblor could damage nine bridges, cut 30 kilometers of electrical cables and 95 kilometers of communication cables.

Carlos Arcilla, director of the UP National Institute of Geological Sciences (NIGS), said earthquakes in Metro Manila could come from three main generators: the West Marikina Valley Fault, the Manila Trench that caused the Jan. 12 earthquake near Olongapo City, and the Philippine Fault System that caused the Luzon earthquake of 1990.

Arcilla said he knew of two private hospitals in the city built on top of a fault line.

“Some builders and owners don’t want to pay a geologist. But they would pay a feng shui expert,” he quipped.

Mahar Lagmay, also of the NIGS and an expert on faults, said the West Marikina Valley Fault had moved four times in the last 1,200 years in intervals of 200 to 400 years.

Due for a big one

The last movement of the fault was recorded at around 200 to 300 years ago.

“I think we are due for a big one. The strain on the fault is building up. So the probability of the fault moving and generating an earthquake is big,” Lagmay said.

As for being prepared for a big earthquake, Adelfo Briones of the Ateneo School of Government, said that the floods brought by Tropical Depression “Ondoy” was the perfect example of how bad local government units (LGUs) responded to a disaster.

“Because of Ondoy, there is some focus on LGU response and really it is more reactive than proactive. The focus is not mitigation. In Metro Manila, LGUs should look at the lay of the land and look at the geological characteristics of their locale,” he said.

Briones is working on a project on the natural disaster preparedness of LGUs.

Ill-equipped to respond

An audit-survey conducted in February 2009 found that a majority of LGUs were not ready to deal with earthquakes and other natural disasters, he said.

“We found that a majority of LGUs are ill-equipped to respond to disasters. There are some good policies and projects, but these are just islands. I’m not saying there are no efforts to mitigate, but the reality on the ground is different. We are a disaster-prone country, so we need to focus on this,” Briones told the Inquirer.

The survey included the skills and training of the LGU disaster-response staff, equipment and even advocacy or information dissemination.

Structural audit

For earthquake mitigation, Briones advocated taking a look at the buildings in a locale.

“How have the laws related to building structure been implemented? That is the big question,” he said.

New buildings have been structurally reinforced, according to Narag. “But I don’t know about the older buildings and some residential houses not built by real estate developers. All the earthquake drills will be useless if the building isn’t stable.”

Architect and urban planner Felino “Jun” Palafox has called for the conduct of a “structural audit” of all private and public buildings to determine their structural integrity.

“New high-rises should be safer because of the strict building permits. I am more concerned with government buildings like public schools and hospitals where shortcuts to getting permits are common due to corruption,” Palafox said.

Building codes

Arcilla said current building codes were “fairly good, if you follow them.”

“Let’s just hope there were no shortcuts taken, and hope for the best,” he said.

Arcilla added that tall buildings built after 1968 “have not been tested by a strong earthquake.”

He pushed for a review of building codes just to be sure but added that the “issue is implementation.”

Binondo, reclaimed areas

Arcilla said tall buildings in the Binondo area could be in danger because of its clay bedrock. “It was swampy before and the bedrock could be prone to liquefaction.”

Tall buildings in reclaimed areas may also be in danger because “the filling can amplify seismic waves more than solid bedrock,” he said.

Solidum said the best earthquake mitigation was “sound engineering practices. When there is a rupture in the ground, don’t build on top of it.”

Earthquake preparedness

At the same time, Solidum said the Phivolcs was active in promoting earthquake preparedness to the public, including making guidelines, providing engineers with data on faults, hazard-mapping, and lectures to schools and other institutions.

“Of course we cannot be 100-percent prepared. Hazard assessments have not changed since the 2004 study. But risk assessment can change since there could be more people coming into areas previously identified as hazardous. This is a continuing issue,” he said.

Metro Manila urged to prepare for big quake

Metro Manila urged to prepare for big quake

Experts say 7-8 magnitude tremor highly probable, the “big quake” feared to hit Metro Manila could happen anytime.

This may be a doomsday prediction, but Arjun Kartoch, head of the Emergency Services Branch of the United Nation’s Office for the Coordination of Humanitarian Affairs, is the bringer of bad news this time, a decade after it was first predicted by seismic experts. He re-issued the warning that an earthquake with a magnitude of about 7 to 8 on the Richter scale would hit the nation's capital region.

But although he was sure that the quake would occur, he did not cite a specific timeframe for the event. He made this announcement on the sidelines of the four-day Second Session of the Global Platform for Disaster Risk Reduction, which started Tuesday to assess strategies to reduce disaster losses around the planet.

During Tuesday’s taping of the BBC show, “World Debate,” hosted by Nik Gowing at the Centre International de Conférences de Genève here, Kartoch provided a picture of magnitude of the tragedy. On the infrastructure side, buildings (hospitals, schools, establishments) and residential houses would collapse, he said, apparently simulating the impact of the quake based on urban congestion, population and buildings’ quake resistance.

“You gonna have 16,000 buildings destroyed. You gonna have … 150,000 who are injured,” said Kartoch. Gowing noted that in that “tragedy,” millions of residents of Metro Manila—with an 18 million population—would be displaced. Kartoch said Senator Loren Legarda and officials of the Philippine government attending the biennial global meeting should prepare for the worst.

Legarda was invited to join the debate as Asia-Pacific’s regional champion for disaster risk reduction (DRR) and climate change adaptation, which put premium on mitigating measures prior to the occurrence of disasters over the current emphasis on post-disaster response such as relief and rehabilitation measures.

The forum, to be broadcast on July 4 to about 80 million global viewers, had Legarda with the other panelists—Kartoch, Guido Bertolaso, head of Italy's Civil Protection Agency, and Edward Borodzicz, professor of risk management at Portsmouth Business School in the United Kingdom. Kartoch did not cite a specific study, but was quoting data culled over the years by the UN OCHA whose mission has been to mobilize and coordinate effective humanitarian action during complex emergencies and natural disasters, said Emmanuel de Guzman.

“Risk reduction is very good and useful, but it should not stop at the point (of disaster),” said Kartoch, who was skeptical of the risk reduction strategy. Legarda noted that the prediction had been discussed for 10 years now. “Thank God, the earthquake did not happen,” she said, informing Kartoch that “preparedness is being done (and) we are prepared for that to the limits of our capabilities and resources.” She said it was unrealistic to relocate now “hundreds of thousands or millions of people” that could be affected.

“But I believe that risk can be reduced,” she said, pointing out that investing in disaster preparedness and risk reduction by building safe hospitals, safe infrastructures, and second, by having risk assessment studies in local government units were essential in mitigating the quake’s impact. “Why build housing projects on earthquake faultlines … at the foot of mountains where there could be landslides … in coastal areas where there are rising sea levels and where there could be storm surges?” she asked.

The senator said that “investment in risk is an investment in lives, not a cost.” She cited Albay province’s investment in mangroves and preemptive evacuation in times of typhoons, and China’s $3 billion investment in flood control which averted $12 billion in losses.

“It’s everybody’s business—international, national, local government units and communities all rolled into one. Not one sector should be (solely) responsible,” she said. De Guzman, UN International Strategy for Disaster Reduction (UNISDR) advisor for Asia-Pacific, confirmed the coming quake, but was unsure when the catastrophic disaster would strike. “The big earthquake is certainly coming. The question is when? No one can tell. It can happen today, tomorrow, or next year. But certainly there will be an earthquake,” De Guzman, who previously worked with the Office of Civil Defense of the NDCC, told the Philippine Daily Inquirer.

On July 16, 1990, an earthquake with a 7.8 Ms (surface-wave magnitude) struck Northern Luzon, producing a 125 km-long ground rupture that stretched from Dingalan, Aurora, to Kayapa, Nueva Vizcaya, as a result of strike-slip movements along the Philippine Fault Zone and the Digdig Fault.

It killed an estimated 1,621 people, with most of the fatalities located in Central Luzon and the Cordillera region. But amidst the latest warning, Legarda expressed optimism that the country could still prepare for an earthquake. She said this was precisely the reason why the UNISDR was pushing for the institutionalization of the DRR, integrating them into the national, regional and local development policies and plans of countries. Legarda, as chair of the Senate committee on health, held an emergency meeting on Wednesday with officials of the Arroyo administration here to assess the preparedness of Metro Manila and institute measures to mitigate the impact of the quake on both population and infrastructure.

“These should be done immediately, within the next 30 days,” she said. “We must have a 30-day prescription of what can be done. It’s doable.” She also invited to the meeting international experts on disaster mitigation such as Turkey and Bangladesh, which has championed community empowerment in drastically arresting disaster fatalities and losses. “We must learn their best practices for possible application in the Philippines in the light of the OCHA doomsday prediction,” she said. Besides Glenn J. Rabonza, executive director of the National Disaster Coordinating Council; Bernaditas Muller, the country’s main negotiator for climate change adaptation; and select officials of the Philippine Institute of Volcanology and Seismology, Department of Health and Department of Science and Technology are attending the DRR second global session.

In an interview, Legarda said the national government, including local government units in Metro Manila, should immediately assess public edifices such as hospitals and schools in terms of their structural integrity to withstand such a massive tremor. The senator said the government should set in place a “metrowide and contingency planning” to prepare for the quake. Legarda said she would ask the DOH to check the bed capacity of all hospitals in the capital region, and for the Department of Public Works and Highways to ensure the safety of commuters and motorists by assessing the quake-resistance of overpasses, bridges, flyovers and roads.

“Condemned buildings, including school dormitories, must be identified immediately, so that residents can be relocated to suitable areas,” she said. “In the event of a strong earthquake, the public should be assured of a steady supply of potable water,” she said, stressing that “lifelines” should continue to be accessible to the public such as communication, roads and safe transportation system. Legarda also pointed the need to check the stability of billboards, which dotted major roads in Metro Manila.

“We should examine their capacities (hospitals and schools), identify evacuation centers like open areas, basketball courts, multipurpose halls that can serve as evacuation centers,” she said. Legarda said the citizens had a pivotal role to play. “We should encourage communities and families to have contingency plans,” she said, adding:

“What should families do when they are separated? Where should they go? The contingency planning should be up to the family unit, the basic unit of society.” Even before sessions resume on July 27, Legarda will conduct consultation hearings to mitigate the impact of earthquake as predicted by UN OCHA.

A study in seismic hazard assessment of Metro Manila was published in 2000 in the Bulletin of Seismological Society of America. The study was conducted by Alan R. Nelson and Stephen F. Personius of the Geologic Hazards Team, Central Region US Geological, and Rolly E. Rimando, Raymundo S. Punongbayan, Norman Tuñgol, Hannah Mirabueno and Ariel Rasdas of the Philippine Institute of Volcanology and Seismology.

The study across the northern part of the west Marikina Valley fault, which lay only 10 km east of central Manila, indicated a recurrence interval of 200-400 years for magnitude 6-7 earthquakes on the fault, it said. It said that a recent assessment of the earthquake hazard posed by crustal faults in cities such as Los Angeles and Seattle, and the economic and human loss resulting from recent damaging earthquakes in Northridge, California, and Kobe, Japan, highlighted the need for evaluating potentially active crustal faults in urban areas. Manila is similarly subject to earthquakes on nearby crustal faults, as well as earthquakes on more distant plate-boundary faults (such as Philippine fault to the east of Manila).

The study did not accurately determine the time of each faulting event or determine specific earthquake recurrence intervals, but said that “empirical relations between rupture lengths and magnitudes of historic earthquakes in similar tectonic environments also argue for earthquakes of magnitude 6-7 on the Marikina Valley fault system.”

The NDCC said that government has been preparing for the very strong quake. Rabonza noted the intensification of earthquake preparedness drills following the recent tremor in Indonesia that killed more than 5,000 persons. But Renato Solidum Jr., director of Phivolcs, said government was using earthquake strength of magnitude 7.2 from the Valley Fault System (formerly known as the Marikina Valley Fault System) "for planning purposes."

If the government failed to prepare, a quake with such magnitude would affect around 38 percent of residential buildings, 14 percent of high-rise buildings and 35 percent of public buildings in the metropolis, he had said.