Earth Observatory Blog

Submitted on 11 Mar 2017 by:

The devastating 2011 Tohoku earthquake in northeastern Japan was a record-breaker on many levels. The magnitude-9.0 quake was Japan’s largest recorded and the world’s fourth biggest earthquake since 1900. Most terribly, it unleashed a 39-metre high tsunami, killing almost 16,000 people and causing a nuclear meltdown at Fukushima Daiichi Nuclear Power Plant.

The earthquake had effects on a global scale. Seismic waves caused icebergs to break off in Antarctica, water in Norwegian fjords to splash back and forth, and wreckage from the tsunami washed up along the North American coastline. Another global consequence? The quake shortened Earth’s day by 1.8 microseconds (µs) and shifted its figure axis by 17 centimetres (cm). 

Just to clear things up, our planet...

Submitted on 29 Nov 2016 by:

In the night of 21 November 2016 (local time), Japan was struck by a magnitude-6.9 earthquake. This was soon followed by a M 5.6 quake in New Zealand’s North Island, which sparked speculation that the event in Japan had triggered the one in New Zealand. 

Dr Wang Yu, a Research Fellow at the Earth Observatory of Singapore, appeared on Channel NewsAsia’s morning news programme, on 22 November 2016, to explain both earthquake events, as well as clarify whether or not this is an indication of more large earthquakes to come.

Below is a short summary of the Q&A segment between Dr Wang and host, Christine Chan:

Q: First Japan, then New Zealand. Are we seeing an awakening of the Ring of Fire?

The Ring of Fire never rests. If we look at historical...

Submitted on 24 Nov 2016 by:

The recent powerful quakes that devastated the northeastern coast of New Zealand’s South Island on 14 Nov 2016 may be part of a pattern emerging for large strike-slip fault earthquakes all around the world.

The New Zealand quakes are significant, because they did not occur on the country’s largest plate-boundary fault line, the Alpine Fault. They instead occurred on smaller nearby faults, and this is something that is happening to other such faults, most notably California’s San Andreas Fault.

New Zealand’s Alpine Fault is a 600-kilometre right-lateral strike-slip fault that forms the main boundary between the Australian and Pacific plates. Its plate movements, considered to be fast by global standards, at ≈ 3 centimetres per year, forged and shaped the Southern...

Submitted on 09 Jun 2016 by:

A magnitude-6.2 earthquake occurred about 300 km southeast of Bali Island on 9 June 2016 at approximately 12.13pm (Singapore Time). Its epicentre is estimated to be close to the Java Trench front with a shallow focal depth from the global seismic network.

Although the tremors from this earthquake were felt by people in Bali and eastern Java, more than 400 km from the epicentre, it is not likely that this earthquake will generate a major tsunami event in Indonesia based on the current estimation of its magnitude.

The Java Trench is located at the southeastern extension of the Sunda Trench, where the Australian plate subducts beneath other tectonic plates along Java and the Lesser Sunda Island. In the past century, the Java Trench has produced more than four major...

Submitted on 04 Jun 2016 by:

Last year, a magnitude-6.0 earthquake rocked the Sabah region of Malaysia. The quake triggered massive rock avalanches on Mount Kinabalu and tragically took the lives of 18 people on the mountain. It included the lives of seven primary school students from Singapore who were on a field trip during their school holidays.

After the earthquake, Dr Wang Yu, a Research Fellow from the Earth Observatory of Singapore (EOS), visited Sabah for a quick post-earthquake survey. There, he found buildings with cracked foundations, caved-in ceilings, and broken pillars that result from the strong ground-shaking motions. The heavy rains that followed after the earthquake caused debris flow, further damaging the area’s bridges and buildings. In total, the quake caused almost S$35 million...

Submitted on 31 May 2016 by:

A magnitude-7.2 deep earthquake occurred offshore northeastern Taiwan on 31 May 2016. This is the second significant quake to have struck northern Taiwan this month, and it was powerful enough to generate strong ground motion throughout the whole of northern Taiwan.

Unlike the shallow Ilan earthquake that had occurred earlier this month on 12 May 2016, the Central Weather Bureau of Taiwan estimated the hypocentre of today’s M 7.2 earthquake to be located approximately 270 km below the seafloor. This suggests that this event is likely to have occurred at the northward subducting slab of the Philippine Sea Plate.

The collision and subduction of the Philippine Sea Plate with the Eurasian Plate are responsible for the creation of the island of Taiwan for the past...

Submitted on 16 May 2016 by:

A magnitude-5.6 earthquake occurred offshore Ilan in northeastern Taiwan on 12 May 2016. According to the United States Geological Survey, this is the second significant quake to have struck Taiwan this year.

Approximately an hour after the M 5.6 mainshock took place, a M 5.5 aftershock occurred east of the mainshock’s point of origin. This series of earthquakes is commonly referred to as a “doublet,” where two quakes of similar magnitudes occur in succession within a relatively short period of time.

The real-time fault-plane solutions1 show that both of these earthquakes were a result of normal faulting.2 Even though it was reported that tremors could be felt as far as northern Taiwan, including Taipei, the degree of ground motion in Taipei was moderate and therefore the...

Submitted on 27 Apr 2016 by:

The concept behind a theme park’s Tipping Bucket water game is simply this: water drips slowly into a bucket and when it becomes completely filled, it tips over to splash the people beneath it.

An earthquake fault acts in the same way. Tectonic stress from a plate’s motion gradually accumulates on the fault plane until it hits a critical level, causing the fault to rupture and generate an earthquake. 

Similarly, one could look at a fault system as being made up of many tipping buckets of different sizes with different filling rates, and containing different amounts of water. When a big earthquake occurs, the ruptured fault will transfer some degree of tectonic stress to nearby faults. To understand this, imagine a large bucket of water tipping over and splashing its...

Submitted on 20 Apr 2016 by:

Japan is known for its earthquakes and tsunami hazards due to the active collision involving three tectonic plates; the Philippine Sea plate, the Pacific plate and the Eurasian plate. These plate convergences not only created the giant trench system found off the eastern Japanese coastline, they also generated a series of active inland faults close to densely populated cities like Osaka, Nagoya, and Tokyo (Fig. 1).

Active faults found on land are usually shorter in length, and move more slowly than those found under the sea in the giant subduction zone where tectonic plates meet. The earthquakes generated by these inland faults are infrequent, and often smaller in magnitude and intensity than the earthquakes in the offshore subduction zone. However, because these inland...

Submitted on 05 Apr 2016 by:

Parkfield, population 18, sits on the San Andreas Fault in central California. Besides a café and grazing cattle, the town hosts a dense array of seismic instruments that measure tremors deep below Earth’s surface. The small quakes repeat every few days and act as a model for similar faults around the world. 

In 2010, David Shelly, a researcher from the United States Geological Survey (USGS), published something puzzling about the Parkfield tremors. Instead of releasing built up stress on a regular schedule, the fault created an alternating waltz-like pattern of tremors, three and six days apart. Not only did the odd rhythm mystify scientists...