DRRR | WW2 Reviewer

The Philippine Institute of Volcanology and Seismology (PHILVOCS)

It is dedicated to providing information on earthquakes, tsunamis. volcanic activity, alongside other specialized information and services towards protecting life and property and supporting economic, productive, and sustainable development. It has stations nationwide to monitor seismic activity

Earthquakes

shaking of earth caused by waves on and below the earth;s surface causing surface shaking, aftershocks, tsunamis, tremors, vibrations, liquefaction, and landslides

Epicenter

point on earth’s surface above the focus

Focus

the origin of the earthquake, usually deep within the earth on a fault

Magnitude

the measure of energy released by an earthquake, only one per earthquake

Intensity

measure of strength produced by the earthquake on a certain location, it is dependent on its effects on the people and surroundings, the distance from the epicenter, and soil type, can vary in different places

Luzon 1990 Earthquake Statistics

• July 16, 1990

• 7.8 Magnitude

• Epicenter was near Rizal, Nueva Ecija

• 1283 Dead

• 2786 Injured

• 321 Missing

• P15.2 B worth of damages

Bohol 2013 Earthquake Statistics

• October 15, 2013

• 7.2 Magnitude

• Epicenter was near Sagbayan

• 156 Dead

• 374 Injured

• 22 Missing

• P2.5 B worth of damages

Surigao 2017 Earthquake Statistics

• February 10, 2017

• 6.7 Magnitude

• Epicenter was near Surigao City

• 300 houses damaged

• 7 bridges collapsed

• P665 M worth of damages

Ground Shaking

the primary cause of earthquake damage to man-made structures, when the ground shakes strongly, buildings can be damaged or destroyed, and their occupants may be injured or killed

Damage of Ground Shaking

The damage depends on topography, geologic conditions, bedrock. location of fault, distance to epicenter

Measuring of Ground Shaking

It is determined by logarithm of the amplitude of waves recorded by a seismograph

Impact of Ground Shaking

damaged structures and infrastructures, injuries, and loss of lives

Reducing Vulnerability to Ground Shaking

• understand how damage from strong shaking occurs

• evaluating and improving earthquake-resistant design strategies and also methods for predicting the seismic performance of structures

Ground Subsidence

lowering of the land surface that is rapidly occurring by a sinkhole, underground mine collapse, or a major earthquake

Impact of Ground Subsidence

• cracked infrastructure

• changes in elevation and gradient of channels

• broken pipes and utility lines

• disrupted damage

• injury

• death

Measuring of Ground Subsidence

• elevation changes

• interferometric synthetic aperture radar (InSAR)

• continuous GPS (CGPS) measurements

• campaign global positioning system (GPS) surveying

Reducing Vulnerability to Ground Subsidence

• public information programs

• maps

• land-use management

Landslide

a general term covering a wide variety of landforms and processes involving the movement of earth, rock, or debris downslope under the influence of gravity

Impact of Landslides

• damage to properties

• disruption transportation (road blockage)

• loss of agricultural sources

• death

Measuring of Landslides

measured with the movements of landmass through monitoring with GPS

Reducing Vulnerability to Landslide

• identify landslide-probe areas

• engineering solutions

• vegetation and landscaping

• water management

• regulation and zoning

Liquefaction

during strong ground shaking, water-saturated soil deposits of fine sand loose their strength and acts like a fluid or “quicksand”, causing the sinking and/or tilting of buildings and structures and the formation of sand boils, most prone are locations near water

Measuring Liquefaction

there is no direct method to to determine the liquefaction potential of a particular location

Reducing Vulnerability to Liquefaction

• ground improvement engineering

• select locations where soil is not predominantly sand

Tsunami

Japanese for “harbor wave,” it originates from undersea/coastal seismic activity, landslides, and volcanic eruptions, and results to sea water being displaced with a violent motion and swells up ultimately surging over land with great destructive power

Signs of Tsunami

• strong ground shaking from an earthquake

• unusual seal-level fluctuations

• abnormally huge wave

• loud ocean roar

Emergency Response to Tsunami

• go to taller places

• perform drop, cover, and hold

Measuring Tsunamis

using a tsunami buoys, they collect data about water level changes through underwater pressure gauges, allowing scientists to predict the wave’s height and when they hit the shore

Causes of Damage from Tsunamis

• high velocity impact of incoming waves

• inland distance of wave run up

• vertical height of wave run up

• inadequate resistance of buildings

• flooding inadequate

Impacts of Tsunamis

• damage to properties

• damage to infrastructures

• death by drowning

Reducing Vulnerability to Tsunamis

• land use management

• planting and environmental preservation

• structural designs

• hazard awareness

• tsunami warning

Faulting/Ground Rupture

the movement along the side of the fault relative to the other due to an earthquake

Damage of Faulting/Ground Rupture

it is measured in distance/area, which increases with magnitude

Impact of Faulting/Ground Rupture

damage to existing structures & infrastructures, broken pipes & utility lines, injuries & death

Reducing Vulnerability to Ground Rupture

• select location far from a fault line

• providing zones where structures may be built

• proper structural and geotechnical engineering designs

Local Risk Reduction Strategies for Earthquake Hazards

• be aware of earthquake risk

• live in houses safe from seismic waves

• sources of open flame and appliances must be made stable and safe

• earthquake and disaster drill

• first aid training groups

General Risk Reduction Strategies for Earthquake Hazards**

• check building codes and attain higher standards of construction quality

• location planning to reduce urban density in areas that amplify ground vibrations

Household Risk Reduction Strategies for Earthquake Hazards

• prepare at least 15 liters of water and food good for at least 72 hours

• prepare a go bag with an emergency kit, important documents, flashlight, portable radio, and clothes

• prepare an evacuation plan, including where to meet and emergency contact numbers

• learn first aid training and how to use fire extinguishers]

• assess house’s structural integrity

Barangay Risk Reduction Strategies for Earthquake Hazards**

• have an alternative water source such as the static water tank

• identify food establishments and pre-position ready-to-eat meals

• retrofit structures, and identify condemned buildings

• identify fuel demands in critical structures

• train at least one person per house hold on first aid

• ensure radio is connected to city or municipality

• update records of residents

Seismology

study of earthquakes and seismic waves that move through and around Earth

Seismic Waves

vibration generated by a sudden impulse in the earth

Seismograph

a complex system/device that records ground movement

Seismometer

the main part of a seismograph that records the motion caused by seismic waves

Types of Waves**

body and surface waves

Body Waves

they travel through interior of the earth, includes primary and secondary waves

Primary Waves

• faster waves

• compress and dilate the matter it passes through to let the matter oscillate parallel to the motion

Secondary Waves

• slower waves

• shears the rock it passes through to let the matter oscillate side-to-side perpendicular to the motion

Surface Waves

slower of the two main types of waves, the ones that do damage in Earthquakes, includes love and rayleigh waves

Love Waves

shake the ground side-to-side like an S wave

Rayleigh Waves

displaces ground like rolling ocean waves

Richter Scale

measurement of magnitude, based on seismic wave size

Mercalli Scale

• measures intensity based on observed effects on people, buildings, and earth’s surface

• qualitative assessment of the impact ranging from I (not felt) to XII (total destruction)

Precautionary Measures Before an Earthquake

• create an emergency plan

• prepare an emergency kit

• secure heavy objects

• reinforce sructure

Precautionary Measures During an Earthquake

• drop, cover, and hold

• stay indoors

• stay away from hazards

• go to an open area if outdoors

Precautionary Measures After an Earthquake

• check for injuries

• prepare for aftershocks

• evacuate if necessary

• listen to official instructions

• check utilities

• document damages

Filling in the table

1. Put the names of the recording stations.

2. Record the S-P interval, Epicentral Distance, Maximum S Wave, and Amplitude.

S-P Interval Measurement

Use the seismometer to measure the distance between the P-wave arrival time and the S-wave arrival time. Keep in mind each vertical lines are spaced at a 2 sec interval.

Epicentral Distance Measurement

Use the S-P interval to determine the corresponding distance.

Maximum S-wave Amplitude

Use the seismometers to determine the maximum amplitude.

Determining Magnitude

1. Plot the S-P epicentral distances and their corresponding max. wave amplitudes on the Ritcher monogram.

2. Draw lines between each pair.

3. Where the lines intersect with each other the magnitude line will determine the magnitude.

Finding the Epicenter on a Map

1. Draw circles around each recording station, with the points for the recording stations acting as the centers of each circle.

2. Use the corresponding epicentral distance as the circles’ radii.

3. The point where all three circles intersect is the epicenter.

Intensity I

not felt except by instruments or favorable conditions

Intensity II

perceived by few people at rest, especially on upper floors

Intensity III

sleepers are awakened; standing motor vehicles may rock slightly

Intensity IV

felt indoors by many; vibrations may be mistaken for a passing truck

Intensity V

felt by most indoors; light sleepers may awaken

Intensity VI

noticeable by many indoors; slight shaking of trees and water

Intensity VII

strong shaking; heavy furniture is displaced

Intensity VIII

furniture overturns; walls may crack

Intensity IX

most people are frightened; heavy damage to weak buildings

Intensity X

general panic; landslides and fissures are likely