Location

Southern Hemisphere, part of New Zealand

Geographic Coordinates

45° S latitude, 169° E longitude

Total Area

150,437 km² (larger than North Island)

Major Cities

Christchurch, Dunedin, Invercargill, Nelson, Queenstown

Population

~1.2 million (as of 2024)

Climate

Oceanic & temperate with alpine regions experiencing snowfall

Notable Natural Features

Southern Alps, Fiordland National Park, Aoraki/Mt. Cook

Seismic Activity

Lies on  Alpine Fault prone to earthquakes

Economic Importance

Agriculture, tourism, viticulture (wine production), hydroelectric power

Notable Earthquakes

2011 Christchurch earthquake (6.3 magnitude), 2025 South Island earthquake (6.7 magnitude)

Definition

A horseshoe-shaped belt of intense seismic & volcanic activity surrounding  Pacific Ocean

Length

~40,000 km

Countries Affected

USA, Canada, Russia, Japan, Philippines, Indonesia, New Zealand, Chile, Peru, Mexico, etc.

Major Tectonic Plates

Pacific Plate, Indo-Australian Plate, Eurasian Plate, North American Plate, Nazca Plate

Seismic Activity

81% of  world’s largest earthquakes occur in this region

Volcanic Activity

Contains 75% of  world’s active volcanoes (~452 volcanoes)

Notable Disasters

2004 Indian Ocean tsunami, 2011 Japan earthquake & tsunami, 2023 Turkey-Syria earthquake

New Zealand's Position

Lies on  boundary of  Indo-Australian & Pacific plates, prone to earthquakes & tsunamis

Risk Factors

Frequent subduction zones, tectonic plate collisions, undersea volcanic eruptions

Oceanic Plates

Thin, dense tectonic plates that primarily form  ocean floor

Pacific Plate, Nazca Plate

High (frequent subduction causes deep-sea earthquakes & tsunamis)

Continental Plates

Thick, buoyant plates forming landmasses

North American Plate, Eurasian Plate

Moderate to High (earthquakes in fault zones, e.g., San Andreas)

Major Tectonic Plates

Largest plates covering Earth's surface

Pacific, Eurasian, Indo-Australian, North American, South American, African, Antarctic

High (major earthquakes occur at plate boundaries)

Minor Tectonic Plates

Smaller plates between major plates

Arabian Plate, Caribbean Plate, Philippine Sea Plate

Variable (depends on proximity to major plate boundaries)

Mariana Trench

Western Pacific Ocean (near Guam)

10,994 m (Challenger Deep)

Pacific Plate vs. Philippine Sea Plate

Deepest trench in  world; home to unique deep-sea life

Tonga Trench

South Pacific Ocean (near Tonga)

10,882 m

Pacific Plate vs. Indo-Australian Plate

One of  most seismically active trenches

Philippine Trench

Philippine Sea

10,540 m

Philippine Sea Plate vs. Eurasian Plate

Known as  "Mindanao Trench"; formed by subduction

Kermadec Trench

South Pacific Ocean (near New Zealand)

10,047 m

Pacific Plate vs. Indo-Australian Plate

Part of  Ring of Fire; close to  Tonga Trench

Puerto Rico Trench

North Atlantic Ocean (near  Caribbean)

8,376 m

North American Plate vs. Caribbean Plate

Deepest part of  Atlantic Ocean; tsunami risk area

Java (Sunda) Trench

Indian Ocean (off  coast of Indonesia)

7,725 m

Indo-Australian Plate vs. Eurasian Plate

Site of  2004 Indian Ocean tsunami

Peru-Chile (Atacama) Trench

Southeast Pacific Ocean

8,065 m

Nazca Plate vs. South American Plate

Generates massive earthquakes & tsunamis

Kuril-Kamchatka Trench

Northwest Pacific Ocean

10,500 m

Pacific Plate vs. Eurasian Plate

High earthquake activity; connected to Japan Trench

Japan Trench

Western Pacific Ocean

8,000 - 9,000 m

Pacific Plate vs. North American Plate

Site of  2011 Tōhoku earthquake & tsunami

Aleutian Trench

North Pacific Ocean (off Alaska)

7,679 m

Pacific Plate vs. North American Plate

Part of  subduction zone responsible for Alaskan earthquakes

Pacific Tsunami Warning Center (PTWC)

Pacific Ocean, Hawaii, U.S. Territories

U.S. NOAA (National Oceanic & Atmospheric Administration)

Monitors seismic activity & sea level changes; issues alerts to 28 member countries

2004 Indian Ocean tsunami, 2011 Japan tsunami

Indian Ocean Tsunami Warning System (IOTWS)

Indian Ocean (South Asia, Africa, Australia)

UNESCO-IOC (Intergovernmental Oceanographic Commission)

Developed after 2004 tsunami; network of deep-sea buoys & tide gauges

2004 Indian Ocean tsunami, 2012 Banda Aceh earthquake

Japan Meteorological Agency (JMA) Tsunami Warning System

Japan & surrounding regions

Japan Meteorological Agency

Advanced real-time seismic & ocean monitoring; uses GPS buoys

2011 Tōhoku earthquake & tsunami

U.S. National Tsunami Warning Center (NTWC)

North America (U.S. & Canada)

NOAA, U.S. Geological Survey (USGS)

Focuses on Alaska, West Coast & Atlantic; issues alerts for regional tsunamis

1964 Alaska tsunami, 2018 Alaska Gulf earthquake

Indonesia Tsunami Early Warning System (InaTEWS)

Indonesia & nearby regions

BMKG (Indonesian Meteorology, Climatology & Geophysics Agency)

Uses seismometers, buoys & coastal sirens

2004 Indian Ocean tsunami, 2018 Sulawesi tsunami

European-Mediterranean Tsunami Warning System (NEAMTWS)

Mediterranean, North Atlantic & Black Sea

UNESCO-IOC

Covers tsunami-prone coastal European regions

2003 Algeria tsunami, 2020 Aegean Sea earthquake

South China Sea Tsunami Advisory Center (SCSTAC)

South China Sea & adjacent areas

China Earthquake Administration

Focuses on regional tsunamis; integrates with global systems

2013 Solomon Islands tsunami

Australia Tsunami Warning System (ATWS)

Australia & surrounding waters

Geoscience Australia, Bureau of Meteorology

Uses deep-ocean buoys, tide gauges & seismic sensors

2007 Solomon Islands tsunami, 2015 Papua New Guinea tsunami

Chile Tsunami Warning System (SHOA - Hydrographic & Oceanographic Service of  Navy)

Pacific Coast of South America

Chilean Navy

Part of Pacific-wide monitoring; integrates with PTWC

2010 Chile earthquake & tsunami, 2015 Illapel tsunami

PRACTICE QUESTION

Q. Explain formation of oceanic trenches & their significance in plate tectonics. How do these trenches contribute to earthquake & tsunami generation?