Philippine Standard Time
 

As of 06:00 PM of 20 December 2024

 

The DOST-PHIVOLCS Philippine Seismic Network has monitored a sequence of earthquakes with preliminary epicenters clustering offshore in the West Philippine Sea, approximately 100 km WNW of Santa Catalina, Ilocos Sur. Since 04:02 AM (PST) of 17 December 2024, a total of 49 earthquakes, with magnitudes ranging between M1.8 to M5.0, were located with epicenters clustering in the same vicinity as shown in Figure 1. The largest earthquake (denoted as yellow star) in the sequence occurred on 19 December 2024 at 09:09 AM (PST) with magnitude M5.0 and focal depth of 27 km, and was reportedly felt in Santa Catalina, Ilocos Sur at Intensity II using the PHIVOLCS Earthquake Intensity Scale.

 

Figure 1. Map showing distribution of earthquakes on 17-20 December 2024 offshore of Ilocos Sur, Philippines

Records of broadband waveforms were processed using the SWIFT system and indicated a predominantly normal mechanism as shown in Figure 2. Based on this mechanism and the epicentral location of these events, this earthquake sequence is associated with the active subduction along the Manila Trench.

Figure 2. Centroid Moment Tensor (CMT) solution using SWIFT showing a predominantly normal mechanism for the M5.0 earthquake

At this stage, the current earthquake activity indicates two scenarios: (a) it may continue with its present activity and eventually decrease in the next few days, or (b) it may intensify and lead to a stronger earthquake that may generate a tsunami. DOST-PHIVOLCS continuously monitors the progress of this earthquake activity. In case of a strongly felt earthquake, DO THE DUCK, COVER, AND HOLD. People in the coastal communities should stay alert and be aware of and monitor the natural signs of an approaching local tsunami - strong ground shaking (SHAKE), sudden and unusual changes in the sea level (DROP), and unusual sound (ROAR). If any of these signs are observed, IMMEDIATELY MOVE TO HIGH GROUNDS OR AWAY FROM THE SHORELINE. Get verified updates from the official website and social media accounts of DOST-PHIVOLCS.

 

Download the PDF copy: https://bit.ly/EQSequence-IlocosSur

 

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