Saturday, 23 June 2012

The Marikina Valley Fault Line: are you ready ?

The Philippine Institute of Volcanology and Seismology (Phivolcs) said  that the Marikina Valley Fault Line, the country’s main fault line which is capable of triggering a 7.2-magnitude earthquake, “is now ripe for movement.” During a Senate hearing, Phivolcs Deputy Director Bartolome Bautista said the Philippines should expect the Marikina Fault line to move “anytime from now.” The Marikina fault line runs from Sierra Madre to Tagaytay City the fault line moves every 200 to 400 years. It moved 200 years ago. The Earthquakes and Megacities Initiative (EMI) report published in 2004 predicts that an earthquake with a high magnitude will surely occur. The United Nations is advising the Philippines to be ready for an upcoming big earthquake.
 A quake with a magnitude of 7.2 or higher on the Richter scale is sure to hit Metro Manila, but the bigger question is when exactly this will happen, no one knows. According to the estimated report, the death toll may reach about 35,000, some 145,000 people may be injured while around 175,000 buildings will be damaged.

Apparently the lack of awareness and preparation of local communities in the event of a massive earthquake and tsunami is the United Nation's main concern.

Earthquakes can not be predicted prior it will happen. Even  the most advance countries in the world can not predict earthquakes. Apparently there are signs and precursors that we can observe hours or even days before the earthquake happens.

Some of these are:

Thermal precursor:
 A few months before the occurrence of an earthquake the average temperature of the area keeps increasing. Weather report bulletins refer to temperatures above or below average by so many degrees. It is seen that in case the area is heading for an earthquake, the average temperature goes on increasing. On the day of the earthquake it is about 5 to 9 degrees Celsius above the average normal temperature for that day. This could be monitored by the meteorology department and also by thermometers inside homes. So it is wise to have a atmospheric thermometer inside our house and to monitor and record the temperature everyday.

Water precursor: 
There is a sudden rise or fall in water level in the wells. It could be as high as one meter. Sometimes the well water may turn muddy. At times a fountain appears inside the well. All these changes happen about one or three days before the earthquake. Sometimes a fountain appears in the ground. This normally happens a few hours before the quake.
Another form of water precursor is seen in the flow of riverwater. There is a sudden and rapid increase or decrease of water flow in the river or nallah. This happens about one to two days before the quake. In wells, the well water may begin to bubble.

Seismo-electromagnetic precursor: 
This is a very reliable precursor. It occurs and is exhibited about 10 to 20 hours before the quake. Before the occurrence of an earthquake the subsurface temperature rises. As a result of this the geomagnetic field is reduced. The reduction in geomagnetic field adversely affects the propagation of electromagnetic waves. This is experienced abundantly on the radio, television and telephone.
If one is tuning the radio at 1000 kHz, then the same station will be received in the potential epicenter area, about 10 to 30 hours before the quake, at higher frequencies. Maybe 1100, 1200, 1300, 1800, 1900, 2000 kHz or so.
Similarly, reception on television is affected by audio, visual and spectral disturbances. The telephone's reception is also adversely affected and there is a continuous disturbance that you can hear.
Apart from this, a recent reliable precursor is the mobile telephone. It has been found that about 100 to 150 minutes before the occurrence of an earthquake, mobile telephones start non functioning or malfunctioning. The time span indicated is sufficient to take all necessary mitigatory measures.

Animal precursor:
It is seen that 10 to 20 hours before the occurrence of an earthquake, the entire animal kingdom becomes highly disturbed and restless. They move in a directionless manner and in fear. Birds do not sit on trees but move about at a low height, emitting a shrill noise. Rodents like rats  are in a panic. Domestic animals like cows, dogs, cats etc struggle against being tied up, and even turn on the owner.

Human precursor:
Doctors and nurses observe that some sensitive patients in hospitals become highly disturbed. They exhibit a sudden rise in blood pressure, heart trouble, headache, migraine, respiratory disorders etc. Further, these psychosomatic signs are manifested without any provocation. It is also seen that the number of patients in the out-patient department increases by five to seven times, some 10 to 20 hours before the quake.
The best indicator is the number of child deliveries in any hospital. On the penultimate day of the earthquake the number of deliveries goes up about three to five times, while on the day of the earthquake it is as high as seven to eight times the normal.

All the above precursors are valid only when seen and manifested extensively. Failure of one or two instruments should not be taken as a seismic precursor.

What to do when it comes ?
Here are some earthquake safety tips to remember.

Before the Earthquake
Arrange your home for safety, Store heavy objects on lower shelves and store breakable objects in cabinets with latched doors. Don’t hang heavy mirrors or pictures above where people frequently sit or sleep. Store flammable liquids away from potential ignition sources. Stock up on emergency supplies. These include: battery operated radio (and extra batteries), flashlights (and extra batteries), first aid kit, bottled water, two weeks food and medical supplies, blankets, cooking fuel, tools needed to turn off your gas, water and electric utilities.

During the Earthquake (you must learn this by heart)
If outdoors, move to an open area where falling objects are unlikely to strike you. If driving, slow down smoothly and stop on the side of the road. Avoid stopping on or under bridges and overpasses, or under power lines, trees and large signs. If indoors, quickly move to a safe location in the room such as under a strong desk, a strong table, or along an interior wall. The goal is to protect yourself from falling objects and be located near the structural strong points of the room.

After the Earthquake
Check for injuries and attend to people who may need help. If the power is out, unplug appliances to prevent possible damage when the power is turned back on. If you smell or hear a gas leak, get everyone outside and open windows and doors. If you can do it safely, turn off the gas at the meter. If the building is badly damaged, evacuate immediately.

Read also Philippines earthquake History

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