Preliminary analysis of volcanoseismic signals recorded at the Tatun Volcano Group, northern Taiwan

Abstract

The Tatun Volcano Group lies at the northern tip of Taiwan only 15 km north of the capital Taipei. A seismic array consisting of 5 stations equipped with both broadband and short‐period sensors was installed in 2003 in order to monitor the seismic activity of the area. It recorded a variety of events including common volcano‐tectonic earthquakes and volcanoseismic signals like tornillos, short duration monochromatic events (10–15 s) and long duration spasmodic bursts (∼15 min). An analysis of the complex frequencies of the tornillo/monochromatic signals shows that Q‐values are of the order of several hundreds. Based on the model of a fluid‐filled crack, such Q‐values can result from the oscillations of a crack containing a misty or dusty gas. These observations put into doubt the long‐standing suggestion that the Tatun volcanoes are extinct and prompt for a thorough assessment of the volcanic hazard for this area.

Deposits, character and timing of recent eruptions and gravitational collapses in Tatun Volcanic Group, Northern Taiwan: Hazard-related issues

“…Although the group has not had any historical eruptions, its volcanic edifices are well-preserved and are dotted by multiple hot springs and solfataras with temperatures up to 116°C (Witt et al, 2008). Detailed investigations undertaken in recent years have provided several lines of evidence that an active magma chamber is present below the TVG: (1) compositions of gases from the TVG fumaroles indicate their origin from a magmatic source (Yang et al, 1999;Lee et al, 2005;Lee et al, 2008;Witt et al, 2008); (2) shallow-level seismicity similar to seismicity under active volcanoes has recently been observed (Lin et al, 2005;Kim et al, 2005;Konstantinou et al, 2007); and (3) geodetic measurements (leveling and GPS) reveal steady local ground deformations of the TVG, which may be caused by pressure changes at depth, possibly associated with migration of magma and/or hydrothermal fluids (Yu et al, 1997;Konstantinou et al, 2007).…”

Characteristics and Origins of Hot Springs in the Tatun Volcano Group in Northern Taiwan

“…Meantime, post volcanic activity, such as wide distribution fumaroles, solfatara and hot springs, helium isotopic data, and core records indicate that a magma chamber may exist underneath the TVG. The TVG, therefore, might still be an active volcano as defined by Szakács (Szakács 1994;Yang et al 1999;Song et al 2000a;Lin et al 2005).…”

“…The volcanoes of the TVG have usually been considered dormant or extinct because no historical eruptions have been recorded. However, a large number of shallow micro-earthquakes, harmonic codas and seismic tremors have been identified showing that a magma chamber may still exist beneath the TVG (Lin et al 2005;Konstantinou et al 2007). High heat flows with geothermal gradients higher than 100°C km -1 were detected through geothermal exploration between 1960s and 1970s (MRSO 1969(MRSO , 1970(MRSO , 1971(MRSO , 1973.…”

Effects of Realistic Surface Topography on Seismic Ground Motion in the Yangminshan Region of Taiwan Based Upon the Spectral-Element Method and LiDAR DTM

“…The area is frequented by hikers, contains a university (the Chinese Culture University), and is located next to the Shilin district, a densely populated outer suburb of Taipei. and Lin, Konstantinou, Liang, et al (2005) presented preliminary results from seismic monitoring of the Datun volcano region that indicates seismic activity beneath the Datun volcanic group characteristic of an active volcanic region. Their results were based upon comparisons with seismic activity studies conducted in known active volcanic regions in other parts of the world.…”