Multiscale effects and drivers of landscape heterogeneity for water-related ecosystem services in urban agglomerations

Understanding the multiscale impacts and drivers of urban agglomeration landscape patterns for ecosystem services (ESs), especially water-related ecosystem services (WESs), is essential for the development of regional ecological management. However, the multiscale impacts and driving mechanisms of urban agglomeration landscape patterns for ESs have not been adequately explained. In this study, multivariate data were employed, and the InVEST model, trend test method, coupled GeoDetector and geographically and temporally weighted regression (GTWR) method were utilized to comprehensively explore the spatial and temporal changes in landscape patterns and WESs in the Pearl River Delta urban agglomeration (PRDUA) at various grid and administrative scales from 1990 to 2020 and to determine the driving mechanisms affecting WESs. The results indicated that the variation characteristics of landscape patterns and WESs in the PRDUA were consistent, forming a binary spatial structure of core and peripheral areas in an inverted “U” shape around the estuary of the Pearl River. The relationship between landscape patterns and WESs weakened with the increase of scale, and the correlation coefficient decreased by approximately 0.10 from 5 km to 10 km grid scale. Additionally, precipitation (PRE) was the main factor controlling WESs changes in the PRDUA, explaining more than 50% of the changes in WESs, and the regression coefficients ranged from 0.0825 to 0.1584. Changes in WESs were the result of the combined effects of natural factors, including PRE, landscape pattern, elevation, slope, and socioeconomic factors, such as population and gross domestic product (GDP). Overall, these findings could contribute to optimizing regional landscape patterns and fostering sustainable development of the ecological environment in urban agglomerations.     

Seismic recurrence parameters for India and adjoined regions

Journal of Seismology - This article focuses on estimating the seismic recurrence parameters of India and adjoining regions based on a comprehensive catalogue assimilated from various sources. The...     

Self-organized Fractal Seismicity of Reservoir Triggered Earthquakes in the Koyna-Warna Seismic Zone,Western India

— Analysis of the Koyna-Warna earthquake catalog (1968–1996) shows that on an average there is a positive correlation between the b value (decrease) and fractal dimensions (decrease in both D₂^s and D₂^t) of earthquake epicenters 0.5 and 2.5 years prior to 1973 (M5.2) and 1980 (M5.5) events, respectively, except a negative correlation for about five years (1988–1993) prior to the 1993/1994 sequence (M5.4). This positive correlation indicates a weaker clustering, or that the epicenters tend to fill the two-dimensional plane. While the origin of the negative correlation seems to be that during periods of large events (low b value), there is strong clustering around the main shock epicenter (high fractal dimension). Interestingly, during the last year (1995–1996) of the studied period both the b value and correlation dimensions rose significantly, suggesting that stress release occurs through increased levels of low magnitude and increasingly scattered seismicity, suggesting an increased risk of larger magnitude events. Incidentally, during 2000 three earthquakes of magnitude M 5.0, one earthquake of M 4.0, 45 earthquakes of magnitude M 3.0–3.9, and several thousand earthquakes of M < 3 have occurred in the region. Thus it can be inferred that at local scales the relationship yields both positive and negative correlation that appears to be controlled by different modes of failure within the active fault complex.Acknowledgement. The authors are grateful to Dr. B.K. Rastogi of NGRI for providing the catalog of Koyna earthquakes and for useful scientific discussions. The comments of Dr. I. G. Main have improved the quality of paper for which we extend to him our sincere thanks. One of the authors (AOM) thanks the Third World Academy of Science and the Council of Scientific and Industrial Research, India for the Postdoctoral Fellowship award under which this work was carried out.     

地震活动相关性定量方法及其在印度板块动力触角对中国西部地区地震影响中的应用

针对地震活动相关性分析的实际需要,提出了一种定量分析不同区域地震活动相关性的方法。以此研究了印度板块东、西触角强震对青藏块体地震活动的影响,结果表明阿萨姆地区的强震活动与青藏块体的强震活动具有很高的相关性,而帕米尔地区的强震影响较小。通过与R值评分及基于板块动力作用分析结果的比较,证实了本方法的有效性。     

近断层脉冲型地震动重要参数的识别方法

在拟合或合成近断层脉冲型地震动的研究中,速度等效脉冲中的参数需要依据实际地震动确定,因此,如何从地震动中识别这些参数就成为一个需要解决的问题.详细分析了已有脉冲周期和脉冲速度峰值的识别方法,分析结果表明这些方法均具有局限性,尤其是对于不规则地震动.提出了基于平滑后的地震动识别脉冲周期和脉冲速度峰值的方法,并验证了这种识别方法的有效性.结果表明: 提出的脉冲周期和脉冲速度峰值识别方法可以克服以往方法的局限性,可以实现脉冲周期和脉冲速度峰值识别的程序化.     

Actinometric determination of turbidity parameters in India

Summary A study of the wavelength exponent of aerosol scattering in the Ångström relation for extinction by aerosol has been made from the ground-based measurments of direct solar radiation using Ångström pyrheliometer with and without Schott filters. It has been observed that in India, mainly for the middle part of the year this exponent is zero or even negative which means that the aerosol scattering is nearly neutral which is in marked contrast with the condition prevailing in middle latitudes. It is evident from the -values that the aerosol size distribution in India is far different from that prevailing in middle latitudes. At four representative stations in India, the values of the wavelength exponent and the atmospheric turbidity coefficient have been determined using the method introduced byÅngström [1,2]) and are discussed here.     

Seismicity and reservoir induced crustal motion study around the Tehri Dam, India

The Tehri Dam is located in a seismotectonically active region in the Indian Himalayan belt. This 260.5 m high dam has a live water storage of 2615 × 10⁶ m³ and is capable of generating crustal deformation corresponding to water fluctuation. Filling of the reservoir started in October 2005. Seismic data around the dam between 2000 and 2010 shows that seismicity is corresponding to drawdown levels of the reservoir rather than to higher water levels. GPS data at twelve local benchmarks were collected from 2006 to 2008 during filling and drawdown reservoir levels. The velocity vectors show ground motion to be between ～0.69–1.50 mm in the different filling-drawdown cycles with reference to the permanent station at Ghuttu. The motion appears to be inwards into the reservoir when the reservoir is filled and outwards when the reservoir is drained. This ground motion corresponds to elastic deformation and rebound due to effect of the oscillating water levels.     

Seismicity and source parameters of earthquakes in the region of the large tolbachik fissure eruption

This study discusses the focal mechanisms of 61 earthquakes and dynamic parameters of 97 earthquakes (m_i, ≥ 2.0 and focal depths 0–20 km) occurring in the region of the large Tolbachik fissure eruption in 1975–1978. Variations of these parameters during the different eruptive stages are examined. Three stages can be distinguished: 1) June 27–July 2, 1975 (from the beginning of the seismic preparation to the large earthquakes of July 2nd withM=5.0); 2) July 2nd-July 6th, 1975 (before the onset of eruption); 3) From July 6th, 1975 to the end of 1976 (during the eruption). During the second stage the 90° reorientation of the compression stress axes was observed; during the third stage the compression stress system returned to the initial strike. No variation in the orientation of the tension stress axes was noted during all these stages. Simultaneously with the reorientation of the compression stress axes in the volcanic earthquake foci during the second stage, the stress-drop values decreased strongly, whereas during the first stage these values were anomalously high. During the third stage the stress-drop values continued to decrease and approached the average regional values indicative of a calm period. All the estimates of parameters variations were made at 0.1 significance level. The above-mentioned temporal variations in the volcanic earthquake focal parameters are discussed in connection with the probable model of preparation and course of eruption.     

Seismicity of the north-eastern region (N.E.R.) of India

Summary The earthquake pattern in the N.E.R. of India is investigated on the background of tectonic conditions. The epicentre maps and the cross-sections indicate some regularities in the spatial distribution of foci, particularly the existence of a Benioff zone, dipping down to 200 km at an angle of 35°–40° to the East between 25° N and 21° N. The shallow and intermediate activities in the Indoburmese zone seem to be mutually related as evidenced by the coincidence of periods of quiescence and activity. The origin of the largest of the whole region (15 Aug. 1950, M=8.6) can be accommodated in the statistics only by assuming a very large preparatory area also encompassing the extended Mishmi region. This event seems to be a rather exceptional event with the return period larger than the sample used for investigation, i.e. 54 years. The problem of a gap in the region of the Upper Assam remains open, the lack of activity also be explained also by pure geological reasons, i.e. by the age of the stable geological formation. The maps and the statistics of extremes provide the estimate of probability of occurrence of large events for practical purpose.     

Crustal Strain Patterns in the Satpura Mountain Belt,Central India: Implications for Tectonics and Seismicity in Stable Continental Regions

The Satpura Mountains of central India represents an ancient orogenic belt of the Mesoproterozoic time. It has a distinct sygmoidal (S-shaped) geometry with long EW and short NE–SW alignments. The mountain belt has been affected by tectonic activities throughout the geological past. The association of high seismicity, high heat flow and high Bouguer gravity anomaly with high topography of the region is a very distinct feature of the mountain range. Present analysis demonstrates that the average velocity for central India has a value of ~54 mm/year towards N050°. The velocity field vector can be partitioned into an eastward component parallel to the Satpura Mountain Belt and a northward component across the belt. The partitioned components provide evidence for sinistral strike–slip deformation of anomalously high shear strain rate of ~3 × 10⁻⁹/year in the region. Similar high shear strain rates are also found from the strain determined by GPS data. An extremely high rate of extensional strain (~600 × 10⁻⁹/year), which is comparable to that of the continental rift systems, is recorded from geodetic data of the Satpura Mountain Belt and the adjacent regions. Regional sinistral shape of the Satpura Mountains involved in a sinistral-slip transtension regime is interpreted to be the cause of high extensional and shear strain regime of the area. The occurrence of normal faulting detected in several deep seismic sounding profiles, the Moho upwarp, crustal thinning, high heat flow and high seismicity of the Satpura region are explained by this tectonic model.     

Seismicity of the Koyna region and regional tectonomagmatism of the Western Margin (India)

Recent findings on the Meso-Cenozoic tectonomagmatism and deep-seated anomalous geophysical structures suggest a close linkage between the seismicity of the Koyna region, the Westernghat uplift (WG-U) and associated thermomechanical and fluid activities. The WG-U seems to be the result of late Cretaceous thermal mobilization, erosion of the Deccan trap cover and superposition of compressional stress. The association of seismicity with uplift seems to result from movement of deep-seated heat and fluids/volatiles along the edges (or boundary faults) of the uplift; because the force required for crustal deformation depends on the relief. Observed gradients in relief may be attributed to the differential erosion-rates and heat inputs, due to the time gap of 50 Ma in the break-ups and plume activities on the eastern and western sides and consequence magmatism. Further, the geology and tectonics strongly indicate that the western margin (WM) is a relic of a mobile arm (MA), that included Madagascar, and which formed a part of the Proterozoic mobile belt of greater India (fort>85 Ma). The mobile nature of the WM facilitates mantle upwellings and transient elevation of isotherms at depth, raising the possibility of intermittent metamorphism and greater deformation.Superposition of the ongoing compression and uplift-induced forces make local permeability and pore-fluid pressure vital in triggering the seismic slip over the Peninsular shield. Certain representative model calculations have been carried out to estimate change in the e.m. induction characteristics caused by an intermittent hydraulic connectivity. The results show a drop in the resistivity which could be a useful monitoring index. The close connection of uplift and fluid activity as discussed here seems applicable for other active parts of the South Indian Shield (SIS) also.     

Genetic algorithms for determining the parameters of cellular automata in urban simulation

This paper demonstrates that cellular automata(CA) can be a useful tool for analyzing the process of many geographical phenomena.There are many studies on using CA to simulate the evolution of cites.Urban dynamics is determined by many spatial variables.The contribution of each spatial variable to the simulation is quantified by its parameter or weight.Calibration procedures are usually required for obtaining a suitable set of parameters so that the realistic urban forms can be simulated.Each pa-rameter has a unique role in controlling urban morphology in the simulation.In this paper,these pa-rameters for urban simulation are determined by using empirical data.Genetic algorithms are used to search for the optimal combination of these parameters.There are spatial variations for urban dynam-ics in a large region.Distinct sets of parameters can be used to represent the unique features of urban dynamics for various subregions.A further experiment is to evaluate each set of parameters based on the theories of compact cities.It is considered that the better set of parameters can be identified ac-cording to the utility function in terms of compact development.This set of parameters can be cloned to other regions to improve overall urban morphology.The original parameters can be also modified to produce more compact urban forms for planning purposes.This approach can provide a useful ex-ploratory tool for testing various planning scenarios for urban development.     

Seismological model parameters for northeastern and its surrounding region of India

A point source seismological model is used in this study to model the available strong motion accelerograms recorded by 17 events and to calculate three seismological model parameters, the source, path, and quality factor. Due to the paucity of recorded events, this is the first time these model parameters have been obtained for the northeastern and its surrounding region of India. The quality factors of the horizontal and vertical components of recorded events with corresponding standard deviations are Q_H(f) = 188.55f^0.94, σ₁ value (25, 0.025) and Q_V(f) = 169.76f^0.93, σ₁ value (20, 0.03), respectively. The source parameter stress drop values (μσ) vary within 124–180 bars for the subduction region and 80–169 bars for the active region. The Kappa factors for the horizontal and vertical components of recorded events on the soft rock site are 0.06 and 0.05, respectively. These seismological model parameters obtained in this study will be useful for future work deriving a ground motion attenuation relation based on a spectral model. Finally, these results are useful for seismic hazard assessment of a region having sparsely recorded events.     

1998年7～9月的全球地震动态

１９９８年第三季度,全球地震活动仍为中等水平,新几内亚北部近海和厄瓜多尔近海各发生一次７级以上地震,亚速尔群岛发生一次６级以上的地震,全球中等以上地震活动无异常现象。     

Source parameters and scaling relations for small earthquakes in Kumaon Himalaya, India

We investigate the scaling relationships among earthquake source parameters using more than 300 good quality broad band seismograms from 30 small earthquakes in the Kumaon Himalaya from the spectral analysis of P and S waves. The average ratio of P/S wave corner frequency is found to be 1.13, which is suggestive of shift in the corner frequency. The estimated seismic moment range from 1.6?×?10¹³–5.8?×?10¹⁵ N?m, while the stress drop varies from 0.6 to 16 bars with 80 % of the events below 10 bars. An analysis of stress drop and apparent stress drop indicates the partial stress drop mechanism in the region. The source radii are between 0.17 and 0.88 km. The total seismic energy varies from 1.79?×?10⁸ to 7.30?×?10¹¹ J. We also observe the variation in seismic energy for a given seismic moment. The scaling relation between the seismic moment and stress drop suggests the breakdown of constant stress drop scaling for the range of seismic moments obtained here for the region. This shows the anomalous behavior of small earthquakes in the region. The study indicates that the stress drop is the dominant scaling factor for the moments studied here.     

Diffuse solar radiation and associated meteorological parameters in India

Solar diffuse radiation data including global radiation, shortwave and longwave balances, net radiation and sunshine hours have been extensively analyzed to study the variation of diffuse radiation with turbidity and cloud discharges appearing in the form of atmospherics over the tropics. Results of surface radiation measurements at Calcutta, Poona, Delhi and Madras are presented together with some meteorological parameters. The monthly values of diffuse radiation and the monthly ratios of diffuse to global solar radiation have been examined, with a special emphasis in relation to the noise level of atmospherics at Calcutta in the very low frequency band. The results exhibit some definite seasonal changes which appear to be in close agreement with one another.     

Self-organized Fractal Seismicity and b Value of Aftershocks of the 2001 Bhuj Earthquake in Kutch (India)

— The devastating intraplate earthquake of M_w 7.7 of 26 January, 2001 took place along the south-dipping reverse fault in the lower crust ( 23 km) of Kutch, Gujarat, India, obliterating some 14,000 people. The aftershock activity has ensued for three years. We analyzed 997 aftershocks of M 3.0 to study the b value and fractal correlation dimensions in time and space. The b value is found to be 0.8 ± 0.03 from the Gutenberg-Richter relation and 0.76 ± 0.02 from the maximum-likelihood, suggesting a typical value for the intraplate region. The spatial correlation is 1.71 ± 0.02, indicating that events are approaching a two-dimensional region. Further, the temporal correlation dimension is estimated to be 0.78 ± 0.02, confirming the structure is mono-fractal in time domain. The depth section of b value shows a peak at 15–35 km depth range coinciding with the maximum occurrence of aftershocks ( 47%), which is inferred as a fluid-filled highly fractured rock matrix with fractures of high density. It will be important to note that tomographic results also suggest a low Vp, low Vs and a large Poissons ratio for the same depth range, further confirming this inference. Additionally, we have studied the variation of D₂^s and b value with time. During the first two months of aftershock activity the results show a marked negative correlation between spatial correlation dimension D₂ (large) and b value (low), indicating the predominance of large events associated with weak clustering. The negative correlation means the stress release along faults of a larger surface area. After two months the fractal dimension (D₂^s) and b value suggests a positive correlation implying more numerous smaller shocks with stress release along faults of a smaller surface area. This would indicate a reduced probability of large magnitude earthquakes due to fragmentation of the fault zone.Acknowledgement. The authors thank Dr. V.P. Dimri, Director, NGRI for his encouragement and kind permission to publish this work. The Department of Science and Technology, New Delhi supported this study.     

Reservoir-induced Seismicity in China

—A review of case histories of reservoir-induced seismicity (RIS) in China shows that it mainly occurs in granitic and karst terranes. Seismicity in granitic terranes is mainly associated with pore pressure diffusion whereas in karst terranes the chemical effect of water appears to play a major role in triggering RIS. In view of the characteristic features of RIS in China, we can expect moderate earthquakes to be induced by the construction of the Three Gorges Project on the Yangtze River.