Showing papers in "Terrestrial Atmospheric and Oceanic Sciences in 2004"

Ionospheric Precursors of Earthquakes; Recent Advances in Theory and Practical Applications

Abstract: This paper accumulates the recent advances in scientific understanding of the problem of seismo-ionospheric coupling. Present research focuses on three main areas: the physical mechanism, main phenomenological features of ionospheric variations associated with earthquakes, and their statistical properties permitting use of them in practical applications. In this paper, the developed physical model bridges the traditional precursors of earthquakes and ionospheric ones, demonstrating that the latter belong to the same family. In this regard the earthquake preparation zone is key generating the scaling law and the relationship between geochemical precursors, anomalous electric field involved in ionospheric variations initiated, and the ionospheric irregularities themselves. Revealed ionospheric precursor phenomena and their statistical parameters are used to develop a pattern recognition technique and other statistical processing techniques that can be used in short-term earthquake prediction. Finally a possible system of ground based measurements and satellite monitoring is proposed for regional and global monitoring and possible short-term prediction of destructive earthquakes.

ULF Geomagnetic Changes Associated with Large Earthquakes

Abstract: Despite its extreme importance and years of effort, practical short-term earthquake prediction still remains to be seen. However, research in earthquake-related electromagnetic phenomena have recently shown that such phenomena make for a promising candidate for short-term earthquake prediction. There is a good deal of accumulated evidence of precursory signatures in a wide frequency range (DC-VHF). ULF geomagnetic change is one of the most promising phenomena and it suggests that short-term prediction is realizable. This report first reviews earlier observational facts and presents the latest results in detection of ULF emissions by means of sophisticated signal processing. Finally, we discuss the possible generation and propagation mechanism of earthquake-related ULF signals.

Long-Range Transport of Asian Dust and Air Pollutants to Taiwan

Abstract: Dust storms and long-range transport of pollutants are major environmental concerns of Taiwan during the winter monsoon season when northeasterly winds prevail following passages of cold fronts. To quantify the impact on air quality, we develop an objective method to classify and study the long-range transport processes by examining the frontal passages in two representative years. We have found that there is about one frontal passage per week in winter and spring, consistent with the climatological average. The long-range transport events are classified into three types according to their degrees of impact on levels of dusts and air pollutants in Taiwan, namely dust storms (DS), long-range transport with pollutants (FP), and long-range transport of background air masses (BG). DS cases occurred 4.7% of the time over 14 months and had a large average PM10 concentration of 127.6 μg m^(-3) at Wan-Li station. FP cases occurred 1.9% of the time and the mean concentration of PM10 during the FP periods was about 85 μg m^(-3). BG cases happened 18.6% of the time and the mean concentration of PM10 was 32.8 μg m^(-3). Dust storms and air pollutants tend to be transported in different air parcels as evidenced by a lack of correlation between dust aerosols and air pollutants. The frequency of local pollution (LP) cases was 71.7% in winter and spring. The average PM10 concentration of LP cases at the Wan-Li station was 47.4 μg m^(-3). However, about one to two-thirds of the PM10 during LP cases can be attributed to the long-range transport. When this contribution is taken into account, we estimate that the contribution of long-range transport to PM10 abundance in northern Taiwan during winter and spring to be in the range of 50% to 75%.

Ionospheric foF2 and TEC Anomalous Days Associated with M ≥ ≥ 5.0 Earthquakes in Taiwan during 1997-1999

Abstract: In this paper, we examine variations in the critical frequency foF2 recorded by an ionosonde, and the total electron content (TEC) derived from a network of 5 ground-based receivers of the global positioning system (GPS), as well as occurrences of 144 M ≥ 5.0 earthquakes in Taiwan during 1997 - 1999. Results show that the foF2 and TEC yield similar tendencies, and often concurrently register pronounced decrease anomalies 4 days before the earthquakes. A detailed investigation of anomalies appearing before and after the earthquakes confirms significant decreases in the foF2 and TEC to be the pre-earthquake anomalies.

Statistical tests for pre-earthquake ionospheric anomaly

Abstract: The anomalous depression of the maximum plasma frequency in the ionosphere (foF2) appears significantly within 1-5 days before the M ≥5.0 earthquakes in the Taiwan area during 1994 - 1999 (Liu et al. 2003). In this paper, we propose two statistical tests against the foF2 anomaly as a candidate for a precursor of earthquakes based on criteria including the success rate, alarm rate, probability gain, and R score. One statistical test is conducted to investigate the significance of the observed foF2 anomalies related to the recorded M ≥5.0 earthquakes in the Taiwan area during 1994- 1999. The other statistical test is designed to compare the foF2 anomaly- based method with competitive alternatives for predicting the earthquakes under study. The involved alternatives are a naive prediction based on a coin-tossing experiment and a simple prediction method constructed from the current M ≥5.0 earthquakes catalog during 1994 - 1999. The simulation results indicate that, contrast to possible foF2 anomalies, the observed foF2 anomalies are significantly earthquake-related. Moreover, comparing with the alternative predictions under study, the foF2 anomaly remains valid for temporal alarming of the M ≥5.0 earthquakes in the Taiwan area during 1994 - 1999.

Relocation of Eastern Taiwan Earthquakes and Tectonic Implications

Abstract: We relocated 6,173 shallow earthquakes and determined focal mechanism solutions of thirty-three M(subscript L)≥5.0 events in the eastern Taiwan region (bounded by 22.7°N, 120.8°E; 24.5°N, 121.5°E; 24.3°N, 122.3°E and 22.5°N, 121.6°E) in order to investigate their tectonic implications. Our resuits suggest that the distribution of the relocated earthquakes generally agrees with the fault plane determined from the focal mechanism solutions. The Longitudinal Valley (LV) is an east-dipping seismic suture zone that separates two different tectonic regions. On the left-hand side of the LV, shallow earthquakes and normal fault-type focal mechanism were found in the Central Range region. But on the right-hand side of the LV, most events that occurred in the Philippine Sea Plate (PSP) were the thrust-type, especially for the southern portion and a few normal and strike-slip focal mechanism events were observed in the northern portion. The tectonics of eastern Taiwan can be classified from south and north into two regions, and there may exist a structure or boundary at about latitude 23.5°N with a strike of N110°E. In the northern portion of eastern Taiwan, the plate boundary appears to be an east-dipping plane defined by the earthquake distribution. The focal mechanism solutions determined in this zone show thrust type faulting and agreed with this boundary plane (strike N20°E and dip about 500). In this region, the Eurasia Plate (EP) dips to the east, and the PSP bends and dips to west. Thus, shallow earthquakes with normal and strike- slip focal mechanisms were observed in the offshore area of this region. On the other hand, the southern part of eastern Taiwan exhibits simple tectonics conditions. The EP subducts to the east under the PSP. The LV is a suture zone dipping to the east, and most events have occurred on the righthand side of the LV. Focal mechanism solutions of these events were thrust-type with strike about N25°E and dip 54° to the east.

Improvement of GPS/MET Ionospheric Profiling and Validation Using the Chung-Li Ionosonde Measurements and the IRI model

Abstract: The retrieval processes of ionospheric profiling from radio occultation observations usually assume spherical symmetry of electron density distribution at the locality of occultation and use the Abel integral transform to invert the measured total electron content (TEC) values. In this paper, we have considered the effect of large-scale horizontal gradient and/or inhomogeneous electron density and developed a compensation procedure for measured TEC values through several close-up occultation observations. The compensated TEC values are then used to yield electron densities through the Abel inversion. In order to assess the accuracy of GPS/MET ionospheric electron density retrievals, coincidences of the Chung-Li digisonde data with observed GPS/MET occultations have been examined. From 232 matches during the GPS/MET mission, the rms fF 02 differences between the digisonde measurements and the GPS/MET retrievals are improved from 1.58 MHz to 1.41 MHz. Further validation of the improved retrieval processes has also been investigated by means of over thirty-eight thousand simulated occultation observations within a reference GPS/MET experiment using the International Reference Ionosphere (IRI) 2001 model. The results show successful improvement of overestimates (underestimates) on low (high) retrieved fF 02 .

Metal Compositions of PM10 and PM(subscript 2.5) Aerosols in Taipei during Spring, 2002

Abstract: Ambient aerosols, collected in Taipei in spring 2002, were measured for concentrations of 15 metals (Al, Ca, Na, Mg, K, Ti, Sr, Ba, Mn, Co, Zn, Pb, Cu, Cd, and Sb). Al was used as a mineral aerosol particle indicator, and based on temporal variations of Al concentration, seven Asian dust storm episodes were identified. The fraction of mineral dust in PM10 was estimated to be around 80% during Asian Dust Storm (ADS) episodes and 15% in non-ADS periods. The metals were categorized into three groups based on their source of origin. The first group consisted of metals from crustal sources, Al, Ca, Sr, Ba, Ti, and Co, the second group was from anthropogenic sources, Pb, Zn, Cd, Cu, and Sb; and the third group was of mixed origins; Na and Mg from sea salt and crustal sources, and K and Mn from crustal and anthropogenic sources. The results of this study demonstrated significant variation in concentrations of metals during spring. Sharp increases in concentration were observed during ADS episodes, particularly for crust-derived elements, Al, Ca, Na, Mg, K, Sr, Ti, Ba, and Co. Metals of anthropogenic origin, Pb, Sb, Cd, and Zn, also increased with ADS episodes, which indicates that significant amounts of pollutant were transported with dust to reach Taiwan. Size-distribution analysis revealed that metals derived from crust and seawater sources (Al, Fe, Sr, Ba, Ti, Na, and Mg) tend to reside in coarse particles, and anthropogenic metals (Pb, Zn, and Cd) in fine particles. Air mass backward trajectory analysis suggested that deserts around Mongolia and the Loess Plateau were the dominant source regions of dust aerosols for ADS. Concentrations of metals in dust were found to change and the wet scavenging affect was strongly indicated.

Mass Concentration and Size-Resolved Chemical Composition of Atmospheric Aerosols Sampled at the Pescadores Islands during Asian Dust Storm Periods in the Years of 2001 and 2002

Abstract: This study investigated the mass concentration and size distribution of atmospheric aerosols collected at the Pescadores Islands during Asian dust storm periods in the years of 2001 and 2002. As part of an island-wide Asian dust sampling network covering Taiwan and its surrounding islands, an atmospheric aerosol sampling site was established at Xiaumen, Pescadores Islands since March 2001. Xiaumen was at the northwest tip of the Pescadores Islands located at the center of Taiwan Strait and approximately 110 kilometers from the West Coast of the Taiwan Main Island. The sampling protocol was conducted to collect sea level atmospheric aerosols for further physical and chemical analysis. This study revealed that five Asian dust storms invaded the Pescadores Islands during the sampling campaign. The mass concentration of atmospheric aerosols, particularly PM(subscript 2.5-1O), were 2-3 times higher than background levels (i.e., non-Asian dust storm periods). Comparison of hourly PM10 concentration between Xiaumen and ambient air quality monitoring stations in Taiwan indicated that Asian dust storms usually invaded from either the northeast or the northwest and could last for approximately 2 - 4 days. Moreover, Asian dusts could be preliminarily validated in situ by observing the change of their apparent colors from dark gray to light brown. Comparison of hourly PM10 concentration measured at the Pescadores Islands and Taiwan Main Island during the Asian dust storm periods showed that the Asian dust storm invaded Taiwan from either the northwest or the northeast. Increasing both concentration and coarse particle mode in the size distribution of atmospheric aerosols validated the invasion of Asian dust storms. Significant increase of SO4(superscript 2-), Cl(superscript -), Na(superscript +), NH4(superscript +), Mg(superscript 2+) and Ca^(superscript 2+) concentration on coarse particle mode was also observed for Asian dusts. This suggested that not just natural soil dusts but also anthropogenic pollutants and oceanic spray could accompany the Asian dust storms and arrive at the Pescadores Islands.

Ethology of the Zoophycos-Producer: Arguments against the Gardening Model from 13 org C Evidences of the Spreiten Material

Abstract: 1 Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan, ROC 2 Department of Geosciences, National Taiwan University, Taiwan, ROC * Corresponding author address: Dr. Ludvig Löwemark, Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan, ROC; E-mail: ludvig@earth.sinica.edu.tw Recently proposed ethological explanations for the trace fossil Zoophycos include gardening of microorganisms. Because microorganisms are known to fractionate strongly against C, especially under low oxic to anoxic conditions, it is argued that any gardening activity in the trace would result in a noticeable shift in δ org C between spreiten and adjacent host sediment. In order to test this hypothesis, δ org C of the Spreiten Material and directly adjacent host material was measured. Measured δ org C in a glacial section of the core ranges from -22.6 to -22.9 0 00 for host sediment and between -22.8 and -23.2 0 00 for Zoophycos material. In an interglacial section the Zoophycos material measures -21.9 0 00 , whereas the host material ranges from -21.2 to -21.4 0 00 . The minimal difference between Zoophycos and host material suggests that gardening plays an insignificant role. The gardening hypothesis is therefore rejected in favor of a cache model, where food is squirreled away for poorer times. (

Stress-Induced Changes in the Electrical Conductivity of Igneous Rocks and the Generation of Ground Currents

Abstract: If we can ever hope to understand the non-seismic signals that the Earth sends out before major earthquakes, we need to understand the physics of rocks under increased levels of stress. In particular we need to understand the generation of electrical currents in the ground. We have begun to study how electrical conductivity of igneous rocks changes under stress and what types of charge carriers are involved. We show that quartz-rich granite and quartz-free anorthosite both generate electronic charge carriers when subjected to stress. The charge carriers are positive holes (p-holes), i.e., defect electrons on the oxygen anion sublattice. They spread out of the stressed rock volume, the “source volume”, into the surrounding unstressed rocks. Time-varying ground currents are required to generate pre-earthquake local magnetic field anomalies and low-frequency electromagnetic emissions. We posit that stress-induced activation of p-hole charge carriers and their outflow from the source volume is the basic process by which ground currents can be generated in the Earth’s crust. We propose that the arrival of p-holes at the Earth’s surface leads to changes in the ground potential that may induce ionospheric perturbations. We further propose that the build-up of high electric fields at the ground surface can ionize the air, hence cause ion emission and corona discharges. When p-holes recombine at the ground surface, they are expected to form vibrationally highly excited 0-0 bonds. The de-excitation of these 0-0 bonds will lead to stimulated mid-IR emission, which may explain the reported pre-earthquake “thermal anomalies” identified in satellite images.

Seismicity Pattern Changes Prior to Large Earthquakes -An Approach of the RTL Algorithm

Abstract: A statistical method, which is called the Region-Time-Length (RTL) algorithm and takes into account information such as magnitude, occurrence time and place of earthquakes, was applied to earthquake data to investigate seismicity pattern changes prior to large earthquakes. Based on the RTL algorithm and some newly developed parameters such as the Qparameter (average of the RTL values over some time window) and S-parameter (an index of seismic activation), I quantified both the temporal and spatial characteristics of seismicity pattern changes in various tectonic regions. The results indicated that seismic quiescence anomalies generally started a few years before the occurrence of the earthquakes and lasted from 1 to 2.5 years. The duration of the subsequent stage of seismic activation generally lasted several months. The linear dimension of the quiescence zone reached a few hundred kilometers (several times the rupture dimension of the mainshock), while the activation zone was generally in order of several tens of kilometers (comparable to the rupture dimension). An earthquake is most likely to occur once the relevant source region has passed through the quiescence and activation stages. Close investigation of possible artifacts due to the selection of model parameters and the changes of seismological networks are important in identifying real seismicity changes from man-made ones. Further stochastic testing using random earthquake catalogs was also done and it supports that the anomalies revealed in my works are significant. Besides studying on seismicity changes before large earthquakes, I also performed the first test of the above statistical method for investigating seismicity changes of earthquake swarms. It indicated that an increased RTL parameter would be a new potentially useful index for the risk alarm of earthquake swarms.

Investigating Subsurface Structures and P- and S-wave Velocities in the Taipei Basin

Abstract: 1 Institute of Geophysics, National Central University, Chung-Li, Taiwan, ROC 2 Energy & Resources Laboratories, Industrial Research Institute of Technology, Hsinchu, Taiwan, ROC 3 Institute of Geography, National Taiwan Normal University, Taipei, Taiwan, ROC * Corresponding author address: Prof. Chien-Ying Wang, Institute of Geophysics, National Central University, Chung-Li, Taiwan, ROC; E-mail: wangcy@cc.ncu.edu.tw Over the past 10 years, the Central Geological Survey (CGS) has conducted a wide-range of investigations of the Taipei basin by drilling over 30 wells (100 700 m). During the same period, we have also scanned the basin area ( 20 20 × km) using over 300 shallow reflection seismic lines. The purpose of this paper is to compile these seismic data, incorporating it with the borehole drilling results, to better describe the Tertiary basement, and the Quaternary layers above the basement including their respective Pand Swave velocities. It is found that 1) the deepest part of the basin basement is probably at the outlet of the Tanshui River, i.e., at the NW corner of the basin, 2) the Kanchiao fault forms a separation boundary bisecting the basin into a deep NW part and a shallow SE part, 3) the Sungshan and Chingmei Formations are relatively flat deposits at the top, which implies the existence of a comparatively quiet deposition period since about 100 thousand years ago, 4) the Pand S-wave velocities inside the basin are 1500 2200 m s and 170 880 m s , and 3000 m s and 1500 m s for the basement. (

Influence of Long-Range Transport Dust Particles on Local Air Quality: A Case Study on Asian Dust Episodes in Taipei during the Spring of 2002

Abstract: In the spring of 2002, an intensive field measurement campaign was conducted to investigate the impact of Asian dust transport on local air quality in Taipei, Taiwan. The mass concentration, size distribution and chemical composition of the atmospheric aerosols were measured. Air quality data collected by the Taiwan EPA during this period were also analyzed. It was found that the content of crustal elements in aerosols could drastically increase on the arrival of air masses transported from the desert areas in Northwestern China and Mongolia. Time series analysis of aerosol measurements, air quality data, and meteorological conditions identified six Asian dust transport episodes occurring in the spring of 2002. In order to apportion the ambient aerosol burden between local and long-range sources, nitrogen oxides (NO(subscript x)) was chosen as a local pollution tracer and a simplified algorithm based on the NO(subscript x) and PM10 correlation was proposed. It was estimated that long-range transported aerosols contributed as much as 87% to the PM10 in Taipei on Feb. 11, the most intense dust event in 2002. A weak event that occurred on Mar. 23 contributed 35% to the PM10. Our results indicate that the air quality impact due to Asian transport dust is still important even during weak dust events.

Comparison of the NDVI, ARVI and AFRI vegetation index, along with their relations with the AOD using SPOT 4 vegetation data

Abstract: For decades, the satellite images acquired in visible and infrared bands have been used for environmental monitoring. In this purpose, the normal­ ized difference vegetation index (NDVI) is the commonly used vegetation index model for canopy monitoring and biomass assessment. However, due to the fact that the NDVI index is susceptible to various outside influences most notably the atmospheric disturbance and currently more bands are provided by satellite platforms additional indexes have been developed to counter these effects. This paper explores two such indexes the Aerosol Free Vegetation Index (AFRI) and the Atmospherically Resistant Vegeta­ tion Index (ARVI). Comparisons were made with the NDVI index to see if they indeed performed better. The relationship of the different outcomes exhibited· between the indexes with the aerosol optical depth (AOD) was analyzed and exploited to see if this scattering effect was more reduced than with NDVI. In general, the results showed that the AFRI and ARVI (with gamma= 1) indeed did perform better than their NDVI counterpart study with the related channels were employed. (

Achievements of NASDA's Earthquake Remote Sensing Frontier Project

Abstract: 311 1Department of Electronic Engineering, the University of Electro-Communications, 1-5-1 Chofugaoka Chofu, Tokyo, Japan 2 Institute of Physics of the Earth, Russian, Academy of Science, Moscow, Russia *Corresponding author address: Prof. M. Hayakawa, Department of Electronic Engineering, the University of Electro-Communications, 1-5-1 Chofugaoka Chofu, Tokyo, Japan; E-mail: hayakawa@whistler.ee.uec.ac.jp After the disastrous Kobe earthquake, the former Science and Technology Agency (STA) of the Japanese Government proposed the Integrated Earthquake Frontier Project. Within the framework of this project, two institutions [RIKEN (Physical and Chemical Institute) and NASDA (National Space Development Agency of Japan)] were asked to carry out over five years a feasibility study of the use of electromagnetic phenomena in short-term earthquake prediction. Since 1996 the RIKEN group has been engaged in the study of earth current and related phenomena. Meanwhile, under the NASDA project named “Earthquake Remote Sensing Frontier Project”, we performed an overal study of seismo-electromagnetic phenomena occurring not only in the lithosphere, but also in the atmosphere and ionosphere. Our five-year study has yielded that the seismic effect expresses itself not only in the lithosphere [such as by ultra low frequency (ULF) electromagnetic emissions, acoustic emissions etc.], but also in the atmosphere and ionosphere (by means of pre-existing transmitter signals). Most importantly, we find convincing evidence for seismo-ionospheric perturbations on the basis of subionospheric very low frequency (VLF) / low frequency (LF) signals. We have established a new challenging scientific field, “Lithosphere-atmosphere ionosphere coupling” or “Electromagnetics in the coupled lithosphere-atmosphereionosphere system”. The study of this coupling would contribute to scientific short-term earthquake prediction. This paper reviews scientific output from our Frontier Project.

Atmospheric field variations before the March 31, 2002 M6.8 earthquake in Taiwan

Abstract: Atmospheric electric field (AEF) observations and other concurrent measurements have been carried out in Taiwan over a three-year period in the context of seismo-electromagnetic studies. Generally, AEF variations appear to be due to meteorological effects. However, there seems to have been a correlation between AEF and the largest M6.8 earthquake on 31 March, 2002.

Aerosol Characterization at Taiwan's Northern Tip During Ace-Asia

Abstract: − , respectively. From the comparisons of particulate matter (PM) mass concentration between YD and non-YD periods, we find an enhance- ment of 110 and 171% in PM 10 and 64 and 96% in PM 2.5 for the two YD events. The enhancement of water-soluble ions is greater in absolute mass concentration but is significantly less in mass fraction. Since major ions like NO 3 − , NH 4 + and SO 4 2− are primarily from anthropogenic sources, their enhancements indicate a significant long-range transport of air pol- lutants from the Asian Continent to the site. Ions like Na + , Cl − , Ca 2+ , and NO 3 − are predominantly distributed in coarse fraction. In contrast, the NH 4 + and SO4 2− are preferentially dis- tributed in fine fraction. Aerosol carbon is enhanced in mass concentration but not in mass fraction for YD samples, and the ratios of OC/EC for both PM 10 and PM 2.5 in each YD sample are similar and almost unvaried with PM concentration. By examining aerosol elemental content, we find that elements such, as Fe, Ti, Si, Ca, K, and Al, are enhanced in YD samples.

Simulations of Asian Yellow Dust Incursion Over Taiwan for the Spring of 2002 and 2003

Abstract: Dust storms that occurred in East Asia during the spring of 2002 and 2003 were simulated by a regional dust deflation and transport model. Particular focus was placed on dust incursion events over Taiwan. Two of the events were analyzed in detail to give a complete picture of the three dimensional transport patterns. The general characteristics of dust incursion events were summarized, including the source locations, transport route and distribution pattern in three dimensions, traveling time, duration of incursion, and the seasonal spatial distribution of dust concentration. Significant differences were also found in these characteristics between the two years, the main cause of which was a change in regional climate patterns. The performance of the model developed for this study was evaluated against other dust forecast models, and found to have superior capability for forecasting in the Taiwan area.

Effects of Reduced Yangtze River Discharge on the Circulation of Surrounding Seas

Abstract: A regional model of the western Pacific Ocean with 1/6o resolution is used to investigate possible effects of reduced Yangtze River discharge on the circulation of surrounding seas. To the extent of data availability, the model is mostly driven by monthly climatological winds and inflows/outflows through open-ocean boundaries. With climatological discharge rate, the Yangtze River plume disperses to the northeast in summer but follows the China Coastal Current (CCC) to the south in winter. While a substantial amount of the summer plume is retained in the southern Yellow Sea and northern East China Sea until the arrival of winter northerly monsoon, the winter Yangtze River discharge is able to escape freely to the south through advection by the CCC. The source water of the CCC is mainly comprised of winter discharge from Yangtze River, remnants of Yangtze River plume water retained in areas northeast of the river mouth from the preceding summer, Yellow Sea water and even some of the Bohai water. The effect of reduced Yangtze River discharge is highly asymmetric between summer and winter. Summer reduction produces an expansive, positive salinity anomaly northeast of the Yangtze River mouth. The response is rather swift and directly proportional to the reduction of freshwater supply. Winter reduction of freshwater discharge from the Yangtze River leads to higher salinity in the CCC south of the river mouth. The winter insensitivity of the CCC to reduced Yangtze outflow arises because the CCC is fed by multiple sources, some of which are not related to winter discharge from Yangtze River. In the highly unlikely event that the Yangtze River discharge is terminated for multiple years, the source water of the CCC will be dominated by the Yellow Sea and even Bohai waters.

Absorption coefficients of colored dissolved organic matter in the surface waters of the East China Sea

Abstract: Seasonal and spatial variations in the sea surface absorption coeffi­ cients of colored dissolved organic matter in the entire shelf of the East China Sea were studied extensively. The absorption coefficients generally showed a decreasing trend from the inner shelf near the China coast to­ ward the offshore direction in all four seasons. The results indicate that more than 75% of the shelf waters belong to the Case 2 water category. It was ascertained that the entire absorption spectra in the UV ( A,= 250 nm) to the Visible (A,= 500 nm) range could not be well-described when only one single exponential decay function was employed. Four discontinuity points at wavelengths of around 250, 275, 325 and 400 nm in the log-trans­ formed absorption spectra were noted. Based on the regressive analysis of a total of 137 absorption spectra, the mean slopes of the exponential decay constant at 250, 275, 325 and 400 nm were 0.018 ± 0.004, 0.025 ± 0.004, 0.015 ± 0.002 and 0.012 ± 0.002 nm·1, respectively. In addition, it was found that the values of the absorption coefficients had a high linear correlation with salinity. This suggests that in terms of mixing, the concentrations of colored dissolved organic matter were mostly conservative. The finding of such a relationship provides researchers with the opportunity to obtain remotely obtain the absorption coefficients of colored dissolved organic matter by using the newly-developed Scanning Low-Frequency Microwave Radiometer (SLFMR) technique. (

Coseismic Movement and Seismic Ground Motion Associated with the 31 March 2002 off Hualien, Taiwan, Earthquake

Abstract: On 31 March 2002, a M L = 6.8 earthquake (called the “331 earthquake”) occurred in northeastern Taiwan off Hualien. The shock lasted over 30 seconds across the entire island of Taiwan. The earthquake caused a few centimeters of coseismic deformation, and a few centimeters of ground motion in the northern and eastern parts of Taiwan. All of these displacements have been recorded by the Taiwan Continuous GPS Array (TCGA), and estimated by two different post-processing methods, namely the daily solution and the kinematic positioning algorithm. Precise evaluation of the coseismic deformation and capturing instantaneous ground motion at a level of just millimeters requires rigorous computational procedures. In this paper, a completely regular algorithm to estimate the crustal deformation in the Taiwan area has been applied to acquire coseismic deformation as a result of the 331 earthquake. A set of high sampling rate (1 Hz) data from the TCGA has been used to study simultaneous ground motion during the 331 earthquake. Using over 18 months of data and 100 stations of the TCGA, the coseismic deformation due to the 331 earthquake can be precisely estimated, and instantaneous ground motion can be observed in that portion of the TCGA network where stations with high sampling rate observations are situated. Since the coseismic deformation can be acquired precisely and the instantaneous ground motion can be computed by continuous GPS observations and integrated with seismic data, these results can aid the study of seismology and earthquake geodesy.

Changes of Geomagnetic Total Field and Occurrences of Earthquakes in Taiwan

Abstract: This paper examines variations in the geomagnetic total field recorded by eight stations in Taiwan from 1989 to 2001. A comparison of data from the international geomagnetic reference field (IGRF) and the eight stations shows that the annual change rates of the field reduce down to ±5 nT/yr in 1997.9. Spatial and temporal analyses demonstrate that a zero isoporic zone (ZIZ) tends to lead to M 6.0 earthquakes within 2 years in the Taiwan area.

A composite study of the synoptic differences between major and minor dust storm springs over the China-Mongolia areas

Abstract: 1 Department of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan, ROC 2 Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Science, Lanzhou, China 3 Inner Mongolia Autonomous Region Meteorological Administration, Hohhot, China * Corresponding author address: Prof. Chung-Ming Liu, Department of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan, ROC; E-mail: liucm@ntu.edu.tw In order to improve the understanding of the mean circulations of and the differences between major and minor dust storm springs over the ChinaMongolia area, multiple-cases, multiple-element circulation composite analyses were conducted utilizing the NCEP/NCAR reanalysis gridded data. The main conclusions are: 1) Based on the differences in the dust storminducing system, dust origin, route of cold air and main dust storm-hit areas, the China-Mongolia dust storms regime can be divided into west, east and Southwest China-Mongolia sub-regimes; 2) During the major dust storm springs in Western China-Mongolia, circulations on the mid-and lowerlevels are characterized by a deeper and stronger Siberian high, dominant troughs or cyclones in and around Mongolia, and intensified westerly winds around the China-Mongolia border, with cold air moving frequently along northwestern or northern routes into China. During minor dust storm springs in Western China-Mongolia, the pattern is altered toward lesser cold air intrusions; 3) During major dust storm springs in Eastern ChinaMongolia, circulations on the midand lower-levels are characterized by the dominant China-Mongolia ridges and troughs or cyclones in and around the Japan Sea, with cold air moving frequently along northeast routes into China; 4) The inter-annual and inter-decadal variations in dust storm occurrences in the last five decades are related closely to the changes in synoptic circulations; and 5) Warming in Mongolia and Southwest Siberia are

Late Holocene Pollen Sequence of the Ilan Plain, Northeastern Taiwan, and its Environmental and Climatic Implications

Abstract: Pollen analysis of a 15.0 m core covering the past 3500 years from the Ilan Plain, northeastern Taiwan, displays a record of environmental changes and climate trends for the late Holocene. At about 3500 yr B.P., brackish water-tolerant elements, such as Bruguiera and Acrostichum, dominated the vegetation, reflecting that the environment was influenced by marine excursions. Following this period, wetland elements Poaceae and Cyperaceae were abundant between ca. 3350 and ca. 3100 yr B.P. Then pioneer taxon Alnus increased at the expense of those herbs in the later part of the interval ca. 3100 and ca. 2000 yr B.P. This suggests a shift from a primarily coastal (ca. 3500 yr B.P.) to wetland (ca. 3350 yr B.P.) and then finally terrestrial (ca. 2000 yr B.P.) environment at the coring site. Since then, the present fluvial plain has existed. Humidity conditions which were interpreted from the amount and variations of fern spore probably indicate a strengthening of the monsoon at ca. 3200, ca. 2000, and ca. 900 yr B.P., respectively. The Medieval Warm Period is also apparent indicated by the amount of arboreal elements based on pollen concentrations ca. 1300 to ca. 900 yr B.P. Significant human-induced vegetation changes occurred between ca. 1300 and ca. 900 yr B.P. and over the last 400 years.

Source Parameters of Regional Earthquakes in Taiwan: January-December, 2002

Abstract: We report on the source parameters of 194 earthquakes that occurred between January and December 2002, in the Taiwan region. The improved CMT inversion algorithm by Kao et al. (1998) is used to overcome the generally higher background noise and the heterogeneous velocity structure resulting from the complex tectonic interactions near Taiwan. To make the results more accessible and useful to the academic community, both the table that summarizes the reported source parameters and the complete set of inversion results are available electronically from the BATS worldwide web site at http://bats.earth.sinica.edu.tw/CMT_Solutions/cmtF2002. html.

A Report from the RIKEN International Frontier Research Project on Earthquakes (IFREQ)

Abstract: Mitigation of seismic hazards requires integration of science and human action, namely the science of earthquakes, anti-seismic engineering and socio-political measures. In this paper, we will be primarily examining the problem of saving human life from earthquakes. Loss of human life from earthquakes is caused overwhelmingly by the collapse of houses and buildings within less than a few minutes of the main shocks. When structural damage is reduced, most other seismic hazards will also be reduced. On top of that, if short-term prediction could be made, casualties would be further reduced dramatically. We review the state of the art in short-term prediction, in particular recent progress in approaches using electromagnetic phenomena. The RIKEN International Frontier Research Project on Earthquakes (IFREQ) has demonstrated the existence of pre-seismic ultra-low frequency (ULF) geo-electric potential changes, a claim that has long been made by the Greek VAN group. In addition, IFREQ has been able to verify the precursory signatures of ULF geomagnetic variations. A review is also made for another promising method using pre-seismic over-the-horizon transmission of VHF (‘100MHz) FM radio waves. Thus, the reinforcement of existing structures and enhancement of short-term prediction research are the two keys for seismic hazard mitigation.

Preliminary Results of the iSTEP Program on Integrated Search for Taiwan Earthquake Precursors

Abstract: The predictability of earthquakes has been a hotly debated question in earthquake science for some time. The answer to which begs another question, “Are there credible earthquake precursors?” Intrigued by these questions and encouraged by instrumental observations of conspicuous ionospheric and geomagnetic disturbances before the disastrous 1999 Chi-Chi earthquake, we decided to undertake an integrated Search for Taiwan Earthquake Precursors, called the iSTEP program. The multidisciplinary program includes five major components aimed at identifying potential seismological, geomagnetic, geodetic and ionospheric precursors, and statistical testing of any identified precursors. Since the program’s inception in April 2002, some encouraging preliminary results have been obtained. These includes precursory P wave travel-time changes six years before the Chi-Chi earthquake, identifiable geomagnetic changes two years before M 6 earthquakes, consistent ionospheric anomalies three days before M 5 earthquakes. We have also developed high-resolution radar interferometric methods for monitoring crustal deformation. A method for forecasting aftershock distribution on the basis of stress transfer has also been successfully tested on the Chi-Chi earthquake sequence. Aided by the newly installed geomagnetic and ionospheric networks we are hopeful about identifying more earthquake precursors and developing relevant physical mechanisms in the remaining two years of the iSTEP program.

An Intensive Mongolian Cyclone Genesis Induced Severe Dust Storm

Abstract: In this paper, a severe dust storm which occurred in northern China is presented and its associated physics investigated. The main sand source regions of this storm were from the Badanjilin Desert in western Inner Mongolia (IM), western Hunshandakend sand lands and the Gobi Desert in southern Mongolia. This dust storm process was a typical cyclonic dust storm, induced mainly by intensive development of a Mongolian cyclone rather than any other weather system. The formation of the strong surface winds was caused not only by the intensive development of a cyclone, and the passage of a cyclonic cold front, but also by a strong meso-scale pressure gradient. The former closely accorded with the severe dust storm while the latter induced the severe prefrontal dust storm. The dust raising mechanism could be described in the following manner: after obtaining much momentum from strong surface winds, the dust was raised upward by strong turbulence in the PBL and then by the systemic ascending motion of a cyclonic system. In addition, divergence-pumping in the upper troposphere indirectly transplanted dust upward.

Application of Space-borne Radar Interferometry on Crustal Deformations in Taiwan: A Perspective from the Nature of Events

Abstract: The orogen of Taiwan is young and active as indicated by the elevation of its topography and dense seismicity. Ongoing crustal deformations therefore cause considerable damage. Taiwan’s high population density means that mitigation of geological hazards has become an urgent task. This paper reviews our recent results using the radar interferometry technique to study crustal deformation in Taiwan. In order to better describe our approach and the limitations of this technique, we have classified crustal deformation into intense and gentle events reflecting different deformation styles. Five case studies of deformation events using DInSAR images have been reported. They are: the coseismic deformation of the Chi-Chi earthquake, uplift of the Tainan area, active deformation of the Hukuo area, rapid land-subsidence in the Chungli area, and seasonal-varied land- subsidence in the Pingtung area. Our results show that this technique is worth developing for future study of neo-tectonic activity and environmental change.