Earthquake too weak for emergency alert: observatory

With many people wondering why an emergency alert was not sent out regarding the earthquake on Monday morning, the observatory gave the following explanation: it was too weak. 

Many in Hong Kong felt vibrations, and some were woke from their sleep after a magnitude 4.1 earthquake struck near the coast of Huizhou city at 2.28am. 

The China Earthquake Networks Centre said the epicenter was located near 22.51N, 115.04E, approximately 92km east-northeast of Hong Kong. The quake struck at a depth of 2.5 km. 

Some citizens questioned why the government did not send an emergency alert this time, after authorities sent out the first message last week using an emergency alert system established in 2020

The observatory responded on its Facebook page that the Short-period Seismograph Network, which collected data from local and global earthquake networks in real-time, can calculate the time, magnitude and epicenter of an earthquake in a few minutes. 

The magnitude of this earthquake was 4.1 but the Observatory generally issues a quick earthquake message when the magnitude reaches 5.0 or above.

In addition, the observatory also needed to analyze the intensity of the earthquake felt in Hong Kong by assessing the information reported by the public, such as where the earthquake was felt and the intensity of tremors.

As to whether the earthquake can be predicted, the observatory stressed that current technologies around the world are unable to accurately predict earthquakes, and it is impossible to give advance warning.

"Earthquakes that cause tremors in Hong Kong usually happen within a few hundred kilometers from the city. They can be felt by instruments and people at the same time,” the observatory wrote.

Nevertheless, the observatory said Hong Kong is hundreds of kilometers away from large seismic zones, such as the Circum- Pacific seismic zone, and is unlikely to be hit by serious earthquakes.

Since the establishment of the Short-period Seismograph Network in 1979, the Observatory has recorded 85 earthquakes that could be felt in Hong Kong, an average of about two per year.

It stressed that although many people felt the tremor this morning, it was not a strong earthquake and the structure of buildings was not be affected. The observatory's 12 radiation monitoring stations in Hong Kong found the ambient radiation level to have remained normal for the past 24 hours.