The swarm has consisted of 147,000 earthquakes, recorded up to the time of the report publication, mostly with magnitudes less than 3.6. Notably, at least 91 very-long-period earthquakes and 89 long-period earthquakes have been detected, indicative of a magmatic body at depth. In addition, at 07:38 on 25 July 2019, a M4 earthquake was located 4 km below the summit of Chiles and felt by residents. About 850 volcano-tectonic events were recorded during 25-28 July.
Source: Smithsonian / USGS Weekly Volcanic Activity Report 31 July-6 August 2019 [less]

However, it has been decreasing overall compared to last year and no events were large enough to be felt recently. [less]

Compared to October and November this year, when daily averages were 3740 and 4579, respectively, seismic activity has declined a lot, but remains high.
The epicenters of most quakes are located a few kilometers south-west of the Chiles volcano. [less]

While most quakes have been very small, a few were strong enough to be felt by local inhabitants.
One possible cause of the earthquake swarm is a magma intrusion at depth, which could be a precursor to new activity of the volcano. This hypothesis is becoming more likely since weak episodes of seismic tremor have started to appear on seismic recordings of stations near the volcano. Tremor are long-lasting regular ground vibrations typical for fluid movements at depth. These could be magma, gasses and/or hydrothermal fluids (water). Which of them is responsible cannot be said at the moment. [less]

This earthquake, located at shallow 10 km depth southwest of the Chiles cone, seems to be directly linked to the ongoing crisis at the volcano. The volcano has recently been showing increased signs of volcanic unrest and inflation. This could be the sign of magma rising with the volcano and result in an eruption, although it is not possible to quantify how likely this might be.
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Most earthquakes were associated with internal rock fracturing and located at shallow 1-7 km depth in an area 4 km SW of the Chiles dome. Magnitudes reached 2.7 and some quakes were felt.
Slight deformation has been detected at the Chiles dome as well. [less]

Most of the earthquakes are volcanic-tectonic, i.e. associated with the fracturing of rock due to fluid pressure underground.
On May 21, 3 earthquakes at 02:53, 15:44 and 18:46 local time were felt felt by local inhabitants. [less]

Colombian and Ecuadorian scientists believe it could be related to shallow magma intrusions. At present, no other signs of unrest that could suggest an eruption in a near or medium future have been detected. [less]

INGEOMINAS reported that seismic activity has remained elevated and that so far, more than 60,000 small earthquakes at shallow depths (1-6 km) have been recorded since November 2013. The epicenters were between 3-5 km SW of the Chiles volcano, while deformation affects neighboring Cerro Negro volcano to the west. Several of them were felt by people living close by. The largest quake so far was a magnitude 4.5 event that was felt widely.
Colombian volcanologists mapped the risk zones for each of the two volcanoes. Neither of them has recorded historical eruptions and little is known about their activity. Whether or not the current unrest leads to an eruption in a near or medium-term future (months, years), and if so, which of the two volcanoes would be involved is unknown. [less]

The seismic record for Cerro Negro volcano goes only back to past November when a small network of seismometers and tiltmeters was installed, so it is not known whether the observed seismic activity is abnormal or part of the normal behavior of the volcano, which last might have erupted in 1936 and has only fumarolic activity at present. In absence of stronger signs of unrest, the alert level of Cerro Negro remains at green for the moment.
The report mentions that a decrease in earthquakes was observed in the first months, while the numbers increased again this March. All quakes were tiny, not exceeding magnitude 1.2. Their hypocenters are located in a cluster a few km SE of Cerro Negro de Mayasquer and mostly between 3 and 5 km depth beneath the summit. [less]