Po-Fei Chen

• Professor
• National Central University

The rupture behavior of intermediate-depth earthquakes in southern Java remains poorly understood despite their potential seismic hazard. In this study, we performed finite-fault inversions to investigate the rupture processes and source characteristics of five intermediate-depth earthquakes (60–300 km depth) with moment magnitudes ≥ 6.1 from 1998...

Luzon Island is a complex setting of seismicity and magmatism caused by the subduction of the South China Sea lithosphere and the presence of a major strike-slip fault system, the Philippine Fault. Previous studies of the structure of this subduction zone have suggested that a ridge subduction system resulted in a slab tearing along the ridge. On t...

In eastern Indonesia, Sulawesi Island lies at the triple junction of the Australian, Sunda, and Phillippine Sea plates. The distinctive K-shape of Sulawesi, consisting of four arms (North, South, East, and Southeast), resulted from continuous geological evolution at different stages. Consequently, each arm has a different deformation style and tect...

An earthquake of M L 4.9 occurred in the mountainous area of Muong Te, Lai Chau in northwestern Vietnam on June 16, 2020, preceded by several foreshocks and followed by a cluster of aftershock. The study region is the most earthquake active region in Vietnam with the present of major faults. In this study, we investigate the characteristics of the...

On July 27, 2020, a shallow earthquake with a moment magnitude (Mw) of 5.0 occurred near Moc Chau in Northwestern Vietnam. Several shallow aftershocks, clustered in a small area, followed the mainshock. The mainshock caused damage to infrastructure in the source area, and considerable shaking was felt in many high buildings in surrounding cities. T...

The Flores Thrust is a southward-dipping, low-to-moderate angle submarine active fault in the eastern Sunda-Banda back-arc (Indonesia). Significant shallow-depth destructive earthquakes have been reported along this fault zone. From 2002 to 2009, one of its fault segments, called the Sumbawa segment, experienced five earthquakes with moment magnitu...

We examine recently released global seismic datasets in 3D visualization to study slab configurations in the Mindanao-Molucca region, where the present-day arc-arc collision of divergent double subduction propagates northward and attains completion on Mindanao Island, Philippines. The activity of inter-plate thrust earthquakes in the Philippine Tre...

Here we dynamically model the temporal development of arc-continent collision, with particular attention to the evolution of slab dip angles and stress fields during approach to collisional locking (suturing). Our modeling is based on a simplified representation of Mindoro Island and the southern Manila Trench, which provide a natural laboratory in...

The 2017 Mw 5.9 Batangas earthquake occurred on a location abutting the Macolod Corridor (MC) to the NE and above the steeply dipping slab of subducted South China Sea lithosphere to the SW. While the spatial distribution of the 2017 Batangas earthquake sequence provides a constraint on the scope of MC’s geothermal activity, the focal mechanisms ar...

First P wave arrival‐time data from local earthquakes recorded by a dense geophone array deployed on the Ilan Plain and by existing permanent stations were combined to invert for high‐resolution P wave velocity structures under northeast Taiwan. With relatively high resolution, we were able to examine the structures in more detail and to investigat...

Receiver function analysis has been widely used to image the subsurface discontinuities from various tectonic settings. In the subduction zone, the results of receiver function analysis could be complicated due to the presence of multiple discontinuities (downgoing slab or low-velocity zone) and complex velocity structure. In this study, we applied...

Calcite (CaCO 3 ) is widely considered an important carbon carrier in the Earth's interior. Laboratory measurements of the velocities and elastic properties of calcite are important for understanding the deep carbon cycle. The sound velocities of calcite were determined up to 10.3 GPa at ambient temperature by Brillouin scattering spectroscopy. Dra...

The southernmost portion of the Ryukyu Trench near the island of Taiwan potentially generates tsunamigenic earthquakes with magnitudes from 7.5 to 8.7 through shallow rupture. The fault model for this potential region dips 10∘ northward with a rupture length of 120 km and a width of 70 km. An earthquake magnitude of Mw 8.15 is estimated by the faul...

The sound velocity properties of single-crystal rhodochrosite (MnCO3) were determined up to 9.7 GPa at ambient temperature by Brillouin scattering spectroscopy. Six elastic constants were calculated by a genetic algorithm method using the Christoffel's equations at each pressure. The elastic constants increased linearly as a function of pressure an...

The Luzon Island, Philippines is the site of two subduction zones: South China Sea subduction in the west and the Philippines Sea Plate in the east. As a consequence of active tectonics, a system of seismicity and volcanic eruption is well developed. To understand the crustal processes in this region, we performed a P-to-S wave receiver function in...

The subduction of South China Sea beneath the Luzon Island has caused a complex setting of seismicity and magmatism because of the proposed ridge subduction and slab tearing. To constrain the validity of slab tearing induced by ridge subduction and their effect, we performed a P and S wave seismic tomography travel time inversion using LOTOS code....

The southernmost portion of the Ryukyu Trench closed to Taiwan island is a potential region to generate 7.5 to 8.7 tsunami earthquakes by shallow rupture. The fault model for this potential region dips 10º northward with rupture length of 120 km and width of 70 km. The earthquake magnitude estimated by fault geometry is Mw 8.15 with 8.25 m average...

The Ilan Plain in northeastern Taiwan is located at a pivotal point where the Ryukyu trench subduction zone, the northern Taiwan crustal stretching zone, and the ongoing arc-continent collision zone converge. In contrast to the North Ilan Plain, the South Ilan Plain exhibits a thin unconsolidated sedimentary layer with depths ranging from 0 - 1 km,...

The Taiwan Island is a result of the convergence between the Eurasia and Philippine Sea plates. To what extent the east-dipping Eurasian slab extends northward beneath central Taiwan and the geometry of the slab east of Taiwan are important issues for understanding the geodynamics of the regional tectonics. However, structures in the upper mantle b...

Here we tackle a tectonically important question – the upper mantle velocity structure beneath central Taiwan – with seismically interesting observations – receiver-side slab waveform effects. We use teleseismic P waveforms of the NS broadband array deployed by the TAIGER project to examine patterns of variation in arrival time, pulse width, and am...

Using Brillouin scattering, we measured the single-crystal elastic constants (C(ij)'s) of a prototypical metal-organic framework (MOF): zeolitic imidazolate framework (ZIF)-8 [Zn(2-methylimidazolate)(2)], which adopts a zeolitic sodalite topology and exhibits large porosity. Its C(ij)'s under ambient conditions are (in GPa) C(11)=9.522(7), C(12)=6....

Array observations indicate that the relative PKP travel-time residuals in the Taiwan region vary from −2.5 to +2.0 s, a range greater than the largest known teleseismic travel-time residuals from deep Earth. PKP waves are generally employed to probe structures of the deep Earth; however, the contribution of shallow geological structures to PKP wav...

Extant paper records of the early analog seismic network of Taiwan represent a large resource for earthquake studies in several disciplines. In this study, we report on T waves generated from offshore earthquakes, based on analog observations. The T phases were identified from their stable apparent velocity of about 1.5 km s(-1) and other observati...

Probing the lateral heterogeneity of the upper mantle seismic velocity structure beneath southern and central Taiwan is critical to understanding the local tectonics and orogeny. A linear broadband array that transects southern Taiwan, together with carefully selected teleseismic sources with the right azimuth provides useful constraints. They are...

The regional spatial variations of teleseismic waveforms reflect lateral velocity perturbations in the crust and upper mantle beneath the receiver array. The waveform effects of a cold, high velocity slab are early arrivals, reduced amplitudes, and broadening waveforms. Taiwan, sitting atop the convergent boundary between the Eurasia and the Philip...

The W-phase inversion has been proven to be an efficient way to determine the magnitude and source mechanism of large earthquakes for tsunami warning purposes (Kanamori and Rivera, 2008). The Institute of Earth Sciences has exchanged seismic data in a real-time manner with other agencies in surrounding countries, including Japan, Vietnam, and Malay...

We characterize fault geometries for moderate and large earthquakes in and offshore southwest (SW) Taiwan. Stress orientation estimates suggest that the first shock of the Pingtung earthquake may be characterized by slab flexure. A region of predominately normal-faulting earthquakes is also defined. Using the maximum-likelihood Gutenberg-Richter re...

The tsunami propagation and coastal run-ups generated by the 2006 Pingtung earthquake doublet is studied numerically. The numerical model - COMCOT, which adopts a modified Leap-Frog finite difference scheme solving nonlinear Shallow Water Equations (NSWE), is employed. The assessment of the tsunami amplitude and extended effects is discussed in thi...

Knowing whether there is a slab of subducted lithosphere beneath central Taiwan is important for our understanding of the regional tectonic evolution. Seismic waves propagating through a slab exhibit earlier arrivals, smaller amplitudes, and broader waveforms relative to those undisturbed. While P waves from Tonga- Kermadec deep and intermediate-de...

A hybrid numerical scheme that simultaneously retrieves single-crystal elastic constants, C-ij, and wave-normal directions is applied to determine the elasticity of natural samples of both magnesite and dolomite, as measured by Brillouin spectroscopy at ambient conditions. The scheme incorporates the genetic algorithm (GA) as a global searching too...

Knowing whether there is a slab of subducted lithosphere beneath central Taiwan is important for our understanding of the regional tectonic evolution. In this study, we aim at resolving this issue by investigating the seismic effects of a potential near-receiver slab, using data from a local broadband array. Rays from deep and intermediate-depth ea...

We examine a variety of mechanisms that have been proposed as contributors to the stress fields expressed as intermediate-depth seismicity in subducting slabs. To this end, we study principal stress orientations for a global data set of 1900 intermediate-depth focal solutions, determining the patterns of events characterized primarily by downdip co...

We use analog seismograms to invert seventeen new centroid moment tensor solutions for shallow earthquakes in the vicinity of Taiwan during the period 1963-1975, with the exact same algorithm used to produce the Harvard catalog for modern events recorded on digital seismographs. The average rate of moment release featured by the 17 events is double...

We propose that the effects of a near-receiver slab is straightforward to observe with a seismic array. While this proposal is globally applicable, the application on data of the "Broadband Array in Taiwan for Seismology (BATS)" is significant for local studies. The Tonga-Kermadec earthquakes exhibit consistently negative travel time anomalies and...

Thesis (Ph. D., Geological Sciences)--Northwestern University, 2002.

The subducting Nazca Plate shows a high degree of along-strike heterogeneity in terms of intermediate-depth seismicity (∼70–300 km), orientations of slab stress, and volcanism. We compile the intermediate-depth earthquakes of South America from the Harvard Centroid Moment Tensor (CMT) catalogue to determine along-strike dip variations, and we explo...

The northwestward subduction of the Pacific plate underneath the Philippine Sea plate exhibits significant along-strike variations both in rate and obliquity. To investigate their effects, we compile intermediate-depth earthquakes ( ~70-300 km) from relocated earthquake hypocenters (Engdahl et al., 1998) to determine the regional slab strike and di...

Centroid moment tensor solutions are presented for 76 intermediate-depth earthquakes (with reported depths between 130 and 300km) covering the years 1962–1975. These solutions are obtained by applying the algorithm used for modern events to restricted datasets of analog (WWSSN) and digital (HGLP) seismograms.

The tsunami propagation and coastal runups generated by the 2006 Ping-Tung earthquake is studied numerically. The numerical model – COMCOT, which adopts a modified Leap-Frog finite difference scheme solving nonlinear Shallow Water Equations (NSWE), is employed. Several possible fault plane mechanisms are examined. The results are compared with the...