EARTHQUAKE- NATURAL HAZARDS

Landslides

occurs when a mass of rock, soil, and debris slides down a slope. Known in mountainous areas that strong earthquakes often result in a significant number of landslides.

INCREASED SHEAR STRESS

The ground shaking introduces additional forces (shear stress ) on the soil and rock masses that make up a slope. If this stress exceeds the shear strength of the material, failure can occur.

LOSS OF SOIL COHESION AND STRENGTH

The vibrations can disrupt and weaken the internal structure of the soil, reducing the cohesion between particles making it more susceptible to sliding. This is particularly true for loose or saturated soils.

Increased Pore Water Pressure

Earthquakes can cause changes in groundwater levels and pore water pressure within the slope. It also reduces the effective stress (the force holding soil particles together), making the slope more susceptible to failure.

TRIGGERING OF PRE-EXISTING WEAKNESSES

Earthquakes don't always initiate landslides from perfectly stable slopes. Often, they act as the final push that triggers a landslide on a slope that was already marginally stable due to factors like: Geological Structures, Geomorphological Features, Hydrological Conditions, Human Activities

Retaining Walls & Drainage Systems

This involves constructing retaining walls and installing drainage systems to manage runoff and prevent further erosion.

Ground Motion and Alarm Systems

The installation of earthquake early warning systems and community preparedness training can greatly enhance resilience.

SOIL REINFORCEMENT: Soil Nailing

Techniques like soil nailing, soil column geotextiles, and geogrids can be used to reinforce the soil mass behind the retaining wall, increasing its resistance to sliding and deformation.

Soil Nailing

Steel bars (nails) are drilled and grouted into the slope to create a reinforced soil mass to resist tensile forces and increase the shear strength of the soil.

CONCRETE CRIB WALLS

are modular, interlocking concrete boxes filled with soil and vegetation.

GEOGRID REINFORCEMENT

strengthens soil layers behind the wall, improving slope stability.

Soil Bioengineering

uses plants like grasses and trees to naturally stabilize slopes and prevent erosion. For the steep area along Lawton Avenue in Taguig City, this method is cost-effective, environmentally friendly, and less disruptive than concrete structures. Techniques like live staking and erosion mats will reinforce the soil while adding greenery. This approach improves slope resilience against landslides and earthquakes

FLOOD

the most frequent type of natural disaster and occur when an overflow of water submerges land that is usually dry.

Flash floods River floods Coastal floods

Three common types of flood:

EARTHQUAKE

a weak to violent shaking of the ground caused by movements within the Earth's crust or volcanic activity. It happens without a warning in all areas around the world.

Tsunamis

These massive waves can travel across entire oceans and cause devastating flooding in coastal areas upon reaching land.

Dam and Levee Failures

Strong shaking can weaken or collapse dams and levees, leading to uncontrolled water release and downstream flooding.

Landslides and Debris Flows

Earthquake-induced landslides can block rivers, forming natural dams. When these unstable dams fail, they release large amounts of water, causing sudden flooding.

Groundwater Level Changes

Earthquakes can alter groundwater levels, sometimes causing a sudden rise that leads to flooding in low-lying areas.

Integrated Flood Management Planning

Engineers integrate flood control into urban design using nature-based solutions that reduce risks while enhancing ecological and social value.

Seismic-Resilient Drainage Systems

Flexible, earthquake-resistant drainage systems ensure continued stormwater management even after seismic events, preventing secondary flood hazards.

Retrofitting and Strengthening Infrastructure

Engineers retrofit vulnerable structures with advanced techniques to withstand seismic forces and maintain flood protection reliability.

Emergency Response Infrastructure

Disaster-ready infrastructure enables rapid, safe evacuation and response by remaining functional and accessible during crises.

Riverbank Reinforcement with Seismic Protection

By using these: Geotextiles: Strengthen soil structure, reduce erosion.

Gabion Walls: Wire baskets filled with rocks that can absorb seismic shock.

Riprap: Loose stones placed along banks to dissipate wave energy and stabilize soil. We can implement this solution. These helps ensure that riverbanks don’t collapse during quakes, reducing risk of flooding from breached waterways.

Riverbank Reinforcement with Seismic Protection

Real Life Example: Location: Kobe, Japan (1995 Earthquake)

Details: After infrastructure collapse due to soil liquefaction and riverbank failure, Kobe upgraded to earthquake-resilient revetments. These structures proved flexible and resistant to shifting ground during aftershocks

Community-Based Flood Monitoring and Warning Systems

Flood sensors: Measure water level and speed in real time.

SMS Broadcasts: Automatically alert residents via text when thresholds are passed.

Installing these systems in the city’s main waterways gives communities time to respond after earthquakes—especially if flooding results from damaged infrastructure or tsunami backflow from the lake.

Community-Based Flood Monitoring and Warning Systems

Real Life Example: Location: Marikina’s Early Warning System

Details: Since Typhoon Ondoy (2009), Marikina installed river sensors, sirens, and traffic light-style warnings, which then sends automated messages into the citizens which significantly reduced loss of life since then.

Smart Flood Control Drainage

An integrated drainage system using one-way backflow valves and automated pumping stations that respond to water levels. These systems stop water from backing up into streets when canals or lakes overflow. It can also automatically redirect water into safer reservoirs or treatment plants.

Smart Flood Control Drainage

Real Life Example: Location: Tokyo’s G-Cans Project

Details: It is a giant underground storm drain system with smartly coordinated pumps and valves. It was activated post-earthquake to divert floodwaters when above-ground drainage is disrupted.

Deployable Modular Flood Barriers

These are portable, reusable flood defenses that can be quickly deployed in anticipation of or immediately following flooding events—especially when triggered by an earthquake. Types include AquaFence (rigid fold-out panels) and HESCO barriers (wire mesh filled with earth or sand).

Deployable Modular Flood Barriers

Real Life Example: Location: Venice, Italy – MOSE Project

Details: MOSE (Modulo Sperimentale Elettromeccanico) is a complex system of inflatable gates that rise from the seabed to block high tides and storm surges from the Adriatic Sea. While MOSE is large-scale, its concept of deployable, site-specific barriers has inspired smaller, modular versions worldwide.

Floating Emergency Structures

These are floating buildings (boats or pontoons) designed to serve as temporary schools, health clinics, or evacuation centers. Built with local materials and often solar powered, they stay operational even when streets are submerged.

Floating Emergency Structures

Real Life Example: Location: Bangladesh’s Floating Schools (Shidhulai Swanirvar Sangstha)

Details: It Operates in flood-prone rural areas with poor road infrastructure. Transforms from transport boats during dry season into education or medical boats during floods, ensuring continuity of services.

Liquefaction

a phenomenon where saturated, loose, granular soils lose their strength and behave like a liquid when shaken by an earthquake, potentialy causing severe ground failure.

DRY MASS STABILIZATION

a ground improvement technique that is used to improve soft or loose soils through the process of mixing the soil with either wet or dry binder.

EARTHQUAKE DRAINS

Earthquake drains are vertical drains filled with gravel or synthetic materials. They provide quick drainage paths for pore water, preventing pressure buildup during shaking.

EARTHQUAKE DRAINS

Earth Tech installs Earthquake Drains for soil liquefaction mitigation using our purpose-built tooling. EQuake Drains function by allowing saturated soils to rapidly drain during an earthquake, preventing liquefaction and the damage it may cause.

VIBRO COMPACTION

Vibro compaction involves inserting a vibrating probe into loose sandy soils to densify them by rearranging soil into a particles tighter packing.

WEST VALLEY FAULT

"The Big One" is a projected magnitude 7.2 earthquake along the West Valey Fault. According to the Metro Manila Earthquake Impact Reduction Study (MIERS), such an event could cause around 34,000 deaths and 100,000 injuries due to building and structural colapses.

DEEP SOIL MIXING

It is proven and reliable technique for mitigating liquefaction. It is also a cost-effective that can enhance the physical and mechanical properties of the soil, providing a stable foundation even under seismic conditions.

The Ring of Fire

also known as the Circum-Pacific Belt, is a path along the Pacific Ocean characterized by active volcanoes and frequent earthquakes. Roughly 90 percent of all earthquakes occur along the Ring of Fire, and it is dotted with 75 percent of all active volcanoes on Earth.

TSUNAMIS/SEISMIC SEA WAVES

a series of ocean waves caused by large, sudden disturbances in the sea, such as earthquakes, volcanic eruptions, or landslides. Earthquakes are the most common cause.

Subduction Zone Earthquakes

Most tsunamis are caused by underwater earthquakes at subduction zones, where one tectonic plate is forced under another.

Sudden Seafloor Uplift or Drop

When a large earthquake occurs, it can cause a sudden vertical displacement (uplift or subsidence) of the ocean floor.

Displacement of Water

This abrupt movement pushes a huge amount of water upward or downward, disturbing the equilibrium of the ocean

Wave Formation

The displaced water spreads out from the epicenter in all directions as a series of waves — these are tsunami waves.

Tsunami Travel

In the deep ocean, these waves travel very fast (up to 800 km/h) but are low in height. As they approach shallow coastal areas, they slow down and grow taller, sometimes reaching heights of over 30 meters.

SEAWALLS AND TSUNAMI BARRIERS

Act as physical barriers to reduce wave energy and prevent flooding

Barriers are like “shields” built close to land to block or redirect waves entirely

OFFSHORE BREAKWATERS

Structures built offshore to dissipate wave energy before it reaches the shore.Breakwaters are like “wave softeners” placed offshore.

ELEVATED STRUCTURES

Designing elevated buildings platforms on or reinforced stilts allows tsunami waves to pass underneath, reducing direct impact.

This method prioritizes vertical evacuation spaces and minimizes structural exposure to hydrodynamic forces.

COASTAL FORESTS

Natural barriers that slow down and reduce wave energy

Mangrove forests or rows of coastal trees.

Enhances biodiversity and protects from erosion in addition to tsunami mitigation.

DEEP FOUNDATION AND SOIL STABILIZATION

Combining steel's tensile strength with concrete's compressive resistance, CFST systems anchor buildings foundations, to deep preventing uplift or displacement.

SEISMIC RETROFITTING

Strengthen the building’s structure to withstand seismic forces by reinforcing walls, foundations, and roof connections.

Carbon-Fibre Belts

used to reinforce the pillars

Post-installed Rebar Connections

Chemical resins were utilized to connect stone wall sections that were not properly interlocked, ensuring the stability of vertical elements.

Shock-Transmitters and Pasty Bushings

these were installed to absorb horizontal seismic forces impacting the structure

Fire suppression system

Implement automatic fire suppression systems such as sprinklers, to quickly control fires that may arise from damaged electrical systems or other hazards.

Flexible Utility Connection

provide mobility, shock absorption and durability, greatly reducing these risks.

Fire-resistant materials

Use this materials for structures and interior finishes to slow the spread of fire in case of an emergency.

Emergency Exit and signage

design clear, accessible emergency exit routes and install visible signage to guide occupants quickly to safety.

Natural sources of seismic waves

Earthquake

Volcanic Eruptions

Landslides

Avalanches

Artifical Sources of seismic waves

Man-made explosions-

Machine vibrations

Density

The speed of the seismic waves depends on __, and we can use the travel-time of seismic waves to map change in density with depth

P Waves

meaning primary waves, travel fastest and thus arrive first at seismic stations

S-waves

meaning secondary waves, waves arrive after the P waves

The Crust

This brittle outermost layer varies in thickness from 25 to 60 km under continents, and from 4 to 6 km under the oceans. Continental crust is quite complex in structure and is made from many different kinds of rocks.

The Mantle

It extends to a depth of 2890 km. It consists of dense silicate rocks. Both P- and S-waves from earthquakes travel through the mantle, demonstrating that it is solid. However, there is separate evidence that parts of the Mantle behaves as a fluid over very long geological times scales, with rocks flowing slowly in giant convection cells.

The Core

At a depth of 2890 km is the boundary between the Mantle and the Earth's Core. The Core is composed of iron and we know that it exists because it refracts seismic waves creating a “shadow zone” at distances between 103º and 143º. We also know that the outer part of the Core is liquid, because S-waves do not pass through it.

TECTONIC

It refers to the structure of the earth and the processes happening on it

Plate Tectonics

The Earth's crust and upper mantle is broken into many plates called tectonic plates that are like pieces of a jigsaw puzzle. There are seven major plates that make up 94% of the Earth's surface and many smaller plates making up the other 6%.

Earth’s Tectonic History

The idea of continental drift was the forerunner of the theory of plate tectonics.

“All Lands”

This giant landmass known as a supercontinent was called Pangea which means

Earthquake

An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction.

Earthquake

When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel.

Divergent or constructive plate boundaries

The plates diverge and this causes the construction of new rock. It happens when two tectonic plates pull apart and rock from the mantle rises up through the opening to form new surface rock when it cools

Convergent or destructive plate boundaries

This is when two tectonic plates move toward each other and collide. The result depends on the type of plates involved. It is possible to have the collision of two oceanic plates, an oceanic plate and a continental plate or two continental plates

Passive plate boundaries

Also known as strike-slip or transform boundaries. This is when two plates slide past each other. When the plates move, the jagged edges of the plate boundaries snag and catch each other and can get jammed. This causes a build-up of pressure. When the plates eventually pass each other, the pressure is released in the form of an earthquake.

Earthquake

It is a transient violent movement of the Earth's surface that follows a release of energy in the Earth's crust.

Magnitude

It is a measure of the amount of energy released during an earthquake and expressed by Richter scale.

Intensity

a qualitative measure of the actual shaking at a location during an Earthquake, and is assigned in Roman Capital Numerical. It refers to the effects of earthquakes. Modified Mercalli scale is the standard measurement.

Intensity

based on the features of shaking, perception by people and animals, performance of buildings, and changes to natural surroundings.

Focus or hypocenter

It is the point within the earth where an earthquake rupture starts

Epicenter

It is the point on the earth's surface vertically above the hypocenter, point in the crust.

Body waves

They move through the interior of the earth, as opposed to surface waves that ravel near the earth's surface.

Body waves: P-wave

A P wave, or compressional wave, shakes the ground back and forth in the same direction and the opposite direction in the direction the wave is moving.

Body waves: S-wave

An S wave, or shear wave, shakes the ground back and forth perpendicular to the direction the wave is moving. S wave can travel only through solids.

Shallow Focus Earthquake

Earthquakes of focus less than 70 km deep from ground surface are called shallow focus earthquakes.

Teleseism

A teleseism is an earthquake recorded by a seismograph at a distance. By international convention the distance is over 1000 Kilometers from the epicenter.

Microseism

These are more or less continuous disturbances in the ground recorded by seismographs

Micro earthquake

A very small earthquake having a magnitude measurable less than three on Richter scale is called a Micro-earthquake.

Accelerogram

The ground acceleration record produced by Accelerograph is called Accelerogram.

Accelerograph

This is an earthquake-recording device designed to measure the ground motion in terms of acceleration in the epicentral region of strong shaking.

Focal distance

The straight-line distance between the places of recording/observation to the hypocenter is called the focal distance.

Intermediate Focus Earthquake

When the focus of an Earthquake is between 70 to 300 km deep it is termed as Intermediate Focus Earthquake.

Epicentral Distance

Distance between epicenter and recording station(in km) is termed as Epicentral Distance.

Foreshocks

Smaller earthquakes preceding the main earthquake results in the generation of Foreshocks.

Aftershocks

Smaller earthquakes following the main earthquake results in the development of aftershocks.

Benioff zone

A region of earthquake activity inclined at an angle underneath a destructive boundary.

Destructive boundary

A part of the earth's crust where tectonic plates move towards one another, resulting in the seduction of one below the other.

Fault

A fracture in the rocks along which strain is occasionally released as an earthquake.