Taal Volcano Eruption 2020 Earthquake Trend

On 12 January 2020, Taal volcano started to erupt spewing ashes to the north of it's crater and nearby areas. It was one of the most frightening natural calamity that we've had to face in recent years. Granted the Philippines is a magnet for nature's wrath with more than a dozen typhoons coming our way annually. Earthquakes are not unusual. But a volcanic eruption, so close to home - 15 km away, is something we have not been ready for.

Phreatic eruption of Taal Volcano, 12 January 2020
Buszmail [CC BY-SA]

When my wife told me ashes are raining down from Taal's eruption, I was very concerned for their safety. I was away working overseas so I did not have first-hand experience. Nonetheless, the devastation that followed affecting the people living near the area was just heart-wrenching. My family was exhausted and stressed out but they emerged unscathed, thankfully. Power and water supply were none existent for more than a week. Everyone was also struggling to find N95 masks to guard against sulfur dioxide particulates from the ash fall. Everywhere one looked, it was gray - covered with ash. The roads were slippery so travelling was discouraged. Many animals and plants bore the brunt and lost their lives.

Time-series animation of the volcanic plume released from Taal Volcano's January 2020 eruption - NASA Earth Observatory

Since then, Taal's volcanic activity seems to have decreased significantly. Philvolcs, the government agency monitoring earthquakes and volcanoes, has lowered the alert level from  4 of 5 to 3 of 5. Although many people were in need of help, I have seen how fellow Filipinos have willingly responded to their aid. For sure, some will not soon forget the experience especially those whose houses were torn by cracks on the ground making them unsafe for shelter.

Still with alert level 3 raised, the situation is far from cleared. The volcano may still yet erupt and that is not comforting. On a daily basis, Philvolcs releases a bulletin about Taal Volcano and its level of activity. The earthquake data that they monitor is a good indication of how active the volcano still is and what is the probability of an eruption in the near future.

The bulletin, however, is sometimes not easy to appreciate. It's a snapshot of what has occurred for the last 24 hours and how Philvolcs interprets the data in terms of it's significance to how an eruption is likely to happen. What it doesn't do is provide a time trend of the number of earthquakes leading up to the eruption and afterwards.

I find this oversight to be puzzling in an agency that should place it's guidance on these kinds of trends. Just to provide a contrast, a stock analyst would always pull out a time based trend of a stock price and the company's financial performance in trying to predict its future value. Although we know their situation is vastly different and could very well be non-scientific in terms of correlation and causation, their method is simple and does make a lot of sense.

But I have to clarify that I do not discount how great a job Philvolcs has done. I commend it's leadership and its people who work tirelessly in the service of every Filipino. They are modern heroes and should always be honored and paid well as much as possible.

Nonetheless, I took it upon myself to generate a chart showing how earthquakes have trended from before the eruption to date. All the data I used are from the bulletin that is posted in Philvolcs web site. You can see the trend chart below which includes the Alert level for that day which means you can see when it changed and the underlying trend for the decisions to change it.

Here are my take from these data:

1. The earthquake counts prior to eruption (still Alert level 1) before the 12th of January is on a slight upward trend but is not wholly indicative whether the volcano is about to erupt
2. The peak earthquake activity happened on the 14th of January (2 days after eruption started) and trended downwards after that
3. Although the start of the eruption caught most everybody off-guard, Philvolcs decided with caution and made the right decision (in my view) in lowering down the alert level from 4 to 3 on the 26th of January when the data is highly convincing
4. The picture doesn't paint how a volcano will behave in the long run but it's indicative that the worst maybe over in the near future

Source: Philvolcs