Ping-Yu Chang

• PhD
• Professor (Full) at National Central University

A massive debris flow induced by Typhoon Morakot buried the southern Taiwan village of Siaolin in Jiaxian township and caused the deaths of an estimated 474 people. To reconstruct the mechanisms triggering the tragic debris flow, researchers must identify the subsurface structures of the debris-flow sediments. For this purpose, we conducted 2-D, el...

The extensive eruption of fluid from the mud volcanoes in the Yanchao area of southwestern Taiwan reveals the activities of the active Chishan fault. A series of time-lapse resistivity imaging measurements were initially conducted in the Wushanting Natural Landscape Preservation Area in Yanchao to evaluate the relationship between resistivity chang...

This study presents a comprehensive approach for constructing a 3D Apparent Geological Model (AGM) by integrating multi-resistivity data using statistical methods, supervised machine learning (SML), and Python-based modeling techniques. Demonstrated through a case study in the Choushui River Alluvial Fan (CRAF) in Taiwan, the methodology enhances d...

The study offers an in-depth investigation of the impact of climate conditions on various terrain features in the Kaffiøyra area, southwest Svalbard, focusing on the changes of shorelines, glacier termini, and outwash areas. We utilized cost-effective, consistent remote sensing data and GIS techniques to analyze historical long-term changes in thes...

This study utilized electrical resistivity imaging (ERI) to investigate subsurface characteristics near Nicolaus Copernicus University Polar Station on the western Spitsbergen-Kaffiøyra Plain island in the Svalbard archipelago. Surveys along two lines, LN (148 m) collected in 2022 and 2023, and ST (40 m) collected in 2023, were conducted to assess...

This study utilized electrical resistivity imaging (ERI) to investigate subsurface characteristics near Nicolaus Copernicus University Polar Station on the western Spitsbergen-Kaffiøyra Plain, island in the Svalbard archipelago. Surveys along two lines, LN (148 meters) collected in 2022 and 2023 and ST (40 meters) collected in 2023, were conducted...

This study presents a pioneering investigation into the complex Holocene paleo-morphologies of the Yilan Plain, located at the southwestern edge of the Okinawa Trough. We employed a novel approach that synergized resistivity measurements with machine learning techniques to unlock valuable insights into the geological history, sedimentary patterns,...

This study presents a pioneering investigation into the complex Holocene paleomorphologies of the Yilan Plain, located at the southwestern edge of the Okinawa Trough. We employed a novel approach that synergized resistivity measurements with machine learning techniques to unlock valuable insights into the geological history, sedimentary patterns, a...

This paper presents an alternative method for monitoring groundwater levels and estimating specific yields of an unconfined aquifer under different seasonal conditions. The approach employs the Time-Lapse Electrical Resistivity Imaging (TL-ERI) method and machine learning-based time series clustering. A TL-ERI survey was conducted at ten sites (WS0...

We used the magnetotelluric method (MT) to investigate near-surface structures at the northern end of the Longitudinal Valley in Hualien City, eastern Taiwan. This valley is considered the suture zone of the arc-continental collision between the Eurasian plate and the Philippine Sea plate, making it crucial to understand the geological settings at...

This data article presents electrical resistivity imaging (ERI) data and inverted models with the objectives of hydrogeological characterization, land subsidence studies, and geological structural detections in Taiwan. The ERI data for hydrogeological studies includes 5 ERI profiles from Changhua, 33 from Yunlin, 36 from Yilan, 23 from Taichung, 23...

We used transient electromagnetic (TEM) to map the hydrogeological structures in the Choushui River Alluvial Fan in Yunlin County of central Taiwan. A total of 63 TEM measurements were collected using the FASTSNAP system with 50 × 50 m in-loop configurations in the middle and distal fan. The 1D model, based on prior information, was constructed fro...

This study aims to apply geophysical methods to determine the Specific Yield (Sy) and Groundwater Level (GWL) in an unconfined aquifer of the Pingtung Plain in South Taiwan. Sy is an important hydraulic parameter for assessing groundwater potential. Obtaining specific yield for a large area is impractical due to the limited coverage and the high co...

Land subsidence will decrease the safety factor of bridges and structures. Many highways and railways constructed decades ago are experiencing damage due to continual land subsidence in several alluvial fans of Taiwan. Groundwater over-pumping for industrial and agricultural uses leads to severe (>3 cm/year) land subsidence in the middle to distal...

Geophysical modelling performs to obtain subsurface structures in agreement with measured data. Freeware algorithms for geoelectrical data inversion have not been widely used in geophysical communities; however, different open-source modelling/inversion algorithms were developed in recent years. In this study, we review the structures and applicati...

Understanding the subsurface geological condition is essential for groundwater investigation. The geophysical method is effectively applied to explore hydrogeological properties and structures. Among geophysical techniques, Transient Electromagnetic Method (TEM) is widely implemented. A TEM data is collected in the Choushui Rivier alluvial fan, Tai...

In this study, we attempt to establish an alternative method for estimating the groundwater levels and the specific yields of an unconfined aquifer for the evaluation of potential groundwater reservoirs. We first converted the inverted resistivity into the normalized water content. Then, we inverted the parameters of the Brooks-Corey model from the...

We aim to develop a comprehensive tunnel lining detection method and clustering technique for semi-automatic rebar identification in order to investigate the ten tunnels along the South-link Line Railway of Taiwan (SLRT). We used the Ground Penetrating Radar (GPR) instrument with a 1000 MHz antenna frequency, which was placed on a versatile antenna...

We examined the uncertainty of the two-dimensional (2D) resistivity method using conceptual cavity models. The experimental cavity study was conducted to validate numerical model results. Spatial resolution and sensitivity to resistivity perturbations were also assessed using checkerboard tests. Conceptual models were simulated to generate syntheti...

We measured electromagnetic responses near tracks of Taiwan's railway system in order to identify the possible influence of these artificial signals, which derive from several types of electric trains. Our power-spectrum analysis shows that the noise frequencies of the "broadband" train signals extend from 10-2 to over 10 Hz after applying the 60-H...

We used the audio magnetotelluric (AMT) method to delineate subsurface re-sistivity structures associated with the western Ilan Plain, which is emerged from the orogenic belt in northeastern Taiwan and is thought to be influenced by the opening Okinawa Trough. The most recent extension phase of the Okinawa Trough starting from approximately 0.1 Ma...

We measured electromagnetic responses near tracks of Taiwan's railway system in order to identify the possible influence of these artificial signals, which derive from several types of electric trains. Our power-spectrum analysis shows that the noise frequencies of the "broadband" train signals extend from 10-2 to over 10 Hz after applying the 60-H...

The southern Sanyi Fault extends across a highly urbanized area in central-west Taiwan. It is within 1–2 km from and generally parallels the northern Chelungpu Fault, which last ruptured in 1999 (Mw = 7.6 Chi-Chi Earthquake) and caused about 2400 fatalities. Several questions thus arise: is the Sanyi Fault likewise active? what is its geometry and...

Electromagnetic (EM) exploration techniques, as powerful and important geophysical tools, have been extensively used in researches ranging from tectonics and resource exploration to environmental and engineering studies. These tools have also proven their applicability to such emerging fields as ocean and airborne surveys. In this article, we quant...

We conducted 2D resistivity survey along nine survey lines and inverted them to 3D model by combining 2D data in the Gunshuiping mud volcano in order to understand: 1) the relationship between the resistivity image and the mud–fluid distribution, and 2) the influences of earthquakes and typhoon on mud volcanoes. The three long survey lines passed t...

Hydraulic conductivity (K) is crucial for groundwater studies and is conventionally obtained through pumping tests, which are costly due to well installation, resulting in a limited amount of data. Recent studies have addressed this limitation by estimating K through the integration of a pumping-test K and electrical resistivity measurements. While...

We constructed an apparent geological model with resistivity data from surface resistivity surveys. We developed a data fusion approach by integrating dense electrical resistivity measurements collected with Schlumberger arrays and wellbore logs. This approach includes an optimization algorithm and a geostatistic interpolation method. We first gene...

Not only direct fault ruptures but also later mass movement may result in complicated frontal deformation of the faults. Consequently, the deformation front or the contacts between the unconsolidated materials from the hanging wall and footwall of the thrust fault may indicate the toe of the mass movement instead of the actual fault zone. In this s...

We conducted time-lapse resistivity imaging during pumping tests at the Pengtsuo and Dajou test sites in Taiwan in order to examine the feasibility of estimating hydrogeological parameters with resistivity variations. Core logs reveal that the subsurface consists mainly of at least 100-m-thick gravel and sand at the two test sites. The resistivity...

The delineation of groundwater recharge zones is crucial for the conservation of groundwater quality and quantity. To objectively estimate groundwater recharge zones, many field surveys are required that are costly in both time and money. To facilitate the assessment of recharge zones with high efficiency and low expense, this study proposes a ‘fas...

Heavy metal contamination commonly appears in mining areas and volcanic watersheds due to the acidic drainage water. Under the hydrochemical condition, the solar photocycle would result in changes of the water temperature, in photosynthesis and in iron photoreduction, which leads to substantial hydrochemical fluctuations, especially for heavy metal...

Electrical Resistivity Imaging (ERI) was carried out continuously for ten days to map the subsurface resistivity distribution along a potentially hazardous hillslope at the Jieshou Junior High School in Taoyuan, Taiwan. The reliability of the inverted resistivity structures down to about 25 m deep was examined with synthetic modeling using the same...

We conducted a time-lapse monitoring study during a well-pumping test at the Pengtsuo site in Pingtung, Taiwan. Water-level gauges were installed in four wells (P1, W1, O1, and O2) at the Pengtsuo site with different screen depths for the observation. We designed the pumping test to be executed in three phases: the background, the stepwise-pumping,...

This study employed the combination of three methods, namely the Frequency Domain Electromagnetic (FDEM), Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) to evaluate a heavy-metal contaminated site for both pre- and post-remediation investigations. The main goals were to verify the position and the integrity of the underg...

In this study, we used the electrical resistivity method for imaging subsurface structures of lake-bottom sediment in Da-Hu Lake in Ilan, Taiwan. Floating passive electrodes were used for the surveys in the study area. We deployed eighteen survey lines across the lake, and executed the survey with the Schlumberger and Wenner array. There are two ge...

The Ilan Plain is located at the southwestern tip of the back arc basin of the Okinawa Trough, which propagates westward into the Taiwan orogen. A long discussed issue concerns whether the opening normal-fault system of the Okinawa Trough propagates and transforms into the thrust-fault system of the Taiwan orogen. We have reprocessed and inverted r...

Double-difference seismic tomography can estimate velocity structure and event locations with high precision, but its high-computation cost along with large memory usage prevents the use of a personal computer to process very large datasets and requires a long-computation time. This work proposes graphics-processing-unit(GPU)-based acceleration sch...

A few studies suggest that infiltration rates within streambeds increase during the flood season due to an increase in the stream stage and the remove of the clogged streambed. However, some studies suggest that a new clogging layer will quickly form after an older one has been eroded, and that an increase in water depth will compress the clogging...

Mud volcanoes (MVs) are considered important methane (CH4) sources for the atmosphere; gas is not only released from macro-seepage, i.e., from craters and visible gas bubbling manifestations, but also from invisible and pervasive exhalation from the ground, named miniseepage. CH4 flux related to miniseepage was measured only in a few MVs, in Azerba...

地熱能由於具有分布廣泛、對環境友善和多方面的應用效能、以及可永續利用，並具有價格低廉和承受較高天然災害的侵襲等特性，是一種極具開發潛力的綠色再生能源。本研究利用清水地熱區所進行之地球物理資料、鑽井與熱液流量紀錄，進行各項想定情境計算清水地區之地熱蘊藏發電潛能。根據計算，若於清水地熱區域同時採取熱液回注開發地熱系統，以及EGS方法開發地熱裂隙系統以外之熱乾岩層地熱蘊藏，在工程可行之情形下，可開發之電量約可達10 MWe。除清水地熱發電裝置容量估算外，我們進一步根據本區地熱蘊藏估算之經驗與參數，利用地溫梯度分佈資料試算宜蘭以及台灣地區之地熱蘊藏潛在發電容量。試算結果發現以宜蘭地區而言，3000公尺深以內範圍之地熱蘊藏約有2.58 GWe之潛在發電容量。而以整個台灣地區而言，3000公尺深以內範圍...

Enhanced Geothermal Systems (EGS) have been used for mining the heat energy from the deep hot dry rocks recently. Unlike the conventional hydrothermal systems, the EGS inject fluids through the injection wells to create enough the fractured reservoir volume that facilitates heat exchange for the injected fluids. The heated fluids were then pumped f...

Hydraulic conductivity (K) is an important aquifer parameter and is usually obtained using conventional pumping test. However, only limited amount of data can be collected, because pumping test is time consuming and expensive. In recent years, some studies estimated K by using pumping test data and surface electrical resistivity survey. These studi...

The purpose of this study is to improve prehistoric knowledge of paleo‐typhoon and winter monsoon activity in the western North Pacific after 8 cal. ka BP. We examine two sediment cores derived from lakes located to the south and north of the Ilan Plain in northeastern Taiwan. Seasonal and typhoon rainfall data over the past several decades are col...

Assessing groundwater recharge area is an important issue for regional groundwater management. The Law on Geological and Mining Activities has recently issued, groundwater recharge area becomes a part of geological sensitivity district which is required higher level survey and protection. This study uses factor analysis to assess the groundwater re...

In the study we attempt to use a wide angle refraction/reflection method, as well as the conventional reflection radargrams to help identify the fractures and cavities in the concrete sea walls retaining a reclaimed land near the campus of National Taiwan Ocean University. First, we acquired GPR reflection radargrams along nine 30-m-long parallel l...

In general, CO2 sequestration by carbonation is estimated by laboratory experimentation and geochemical simulation. In this study, however, estimation is based on a natural analogue study of the Miocene basalt in the Kuanhsi-Chutung area, Northwestern Taiwan. This region has great potential in terms of geological and geochemical environments for CO...

To analyse the resolution and accuracy of cross-borehole ground penetrating radar (XBGPR) methods in monitoring the variation due to fluid infiltration in the heterogeneous vadose zone, we built a hypothetical two-dimensional model by using the Sandia-Tech Vadose Zone (STVZ) model for unsaturated-flow modelling. The spatial variation in water conte...

AbSTRACT We conducted 2D and 3D looped resistivity surveys in the Wushanting Natural Landscape Preservation Area (WNLPA) in order to understand the relationships of the mud-fluid conduits in the mud volcano system. 2D resistivity surveys were conducted along seven networked lines. Two separate C-shape looped electrode arrays surrounding the volcano...

A two-stage salt infiltration experiment was conducted to simulate vadose zone contaminant transport and to investigate mechanisms that affect the development of contaminant plumes in the unsaturated zone. A low-concentration sodium chloride solution (1024 ppm) was first infiltrated for 7 months through one third of a specially designed infiltromet...

Cross-borehole ground penetrating radar (XBGPR) is used in monitoring a long-term vadose zone infiltration experiment at a test site in Socorro, NM in order to examine contaminant transport in the vadose zone. XBGPR attenuation tomography is conducted in order to test the ability of using images of electromagnetic attenuation for hydrogeologic inve...

Cross Borehole Ground Penetrating Radar (XBGPR) is used in monitoring a series of vadose zone infiltration experiments at a test site in Socorro, New Mexico in order to examine contaminant transport in the vadose zone. A water-infiltration and two-stage salt infiltration experiment were conducted at this site in order to investigate flow and solute...

Experiments have been conducted to demonstrate the accuracy and precision of moisture content estimates derived from cross-borehole ground penetrating radar (XBGPR) measurements made within the vadose zone. Both numerical simulations and field data demonstrate that although a certain amount of image smearing occurs under ideal conditions the genera...

Summary Cross Borehole Ground Penetrating Radar is currently being used to monitor the change in moisture content and to test the feasibility of using attenuation tomography in order to monitor the conductive solute transport in the vadose zone at a test site in Socorro, New Mexico. The test site is a fluvial deposit containing alternating layers o...