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 earthquake records, this year we’ve had a magnitude-7.8 earthquake that happened in South America. Last year in November, there was a M 7.6 quake. So, in fact, these kinds of events are constantly happening around the Ring of Fire.
Q: Can we expect more of these seismic events and activities, especially here in Asia and the Pacific?
Around the Pacific Ocean, these kinds of events are always happening. Often, there are strong aftershocks that follow a large earthquake. The event that happened just this morning could be an aftershock of the magnitude-9.0 earthquake that took place about five years ago in Tohoku-Oki, Japan.
Q: That’s a very interesting point that you have brought up. Is there a difference for you, the professional observer, between the event in Japan and the event in New Zealand today? They must be in response to something, and are not earthquakes per se.
Both of them are indeed aftershocks. One is an aftershock that followed the main event five years later, and one just several days later. So they share similar characteristics, but the thing that is different is their focal mechanisms (the source of the earthquakes).
For example, the Japan earthquake happened on a normal fault above the subduction zone interface. This is not very common in aftershocks. But, in New Zealand, this earthquake could have happened on the subduction zone interface or a reverse fault related to the subduction process.