From transpression to transtension: changes in morphology and structure around a bend on the North Anatolian Fault in the Marmara region

The east–west-trending North Anatolian Fault makes a 17° bend in the western Marmara region from a mildly transpressional segment to a strongly transtensional one. We have studied the changes in the morphology and structure around this fault bend using digital elevation models, field structural geology, and multi-channel seismic reflection profiles. The transpression is reflected in the morphology as the Ganos Mountain, a major zone of uplift, 10 km wide and 35 km long, elongated parallel to the transpressional Ganos Fault segment west of this bend. Flat-lying Eocene turbidites of the Thrace Basin are folded upwards against this Ganos Fault, forming a monocline with the Ganos Mountain at its steep southern limb and the flat-lying hinterland farther north at the flat limb. The sharp northern margin of the Ganos Mountain coincides closely with the monoclinal axis. The strike of the bedding, and the minor and regional fold axes in the Eocene turbidites in Ganos Mountain are parallel to the trace of the Ganos Fault indicating that these structures, as well as the morphology, have formed by shortening perpendicular to the North Anatolian Fault. The monoclinal structure of Ganos Mountain implies that the North Anatolian Fault dips under this mountain at 50°, and this ramp terminates at a decollement at a calculated depth of 8 km. East of this fault bend, the northward dip of the North Anatolian Fault is maintained but it has a normal dip-slip component. This has led to the formation of an asymmetric half-graben, the Tekirdağ Basin in the western Sea of Marmara, containing a thickness of up to 2.5 km of Pliocene to Recent syn-transform sediments. As the Ganos uplift is translated eastwards from the transpressional to the transtensional zone, it undergoes subsidence by southward tilting. However, a morphological relic of the Ganos uplift is maintained as the steep northern submarine slope of the Tekirdağ Basin. The minimum of 3.5 km of fault-normal shortening in the Ganos Mountain, and the minimum of 40 km eastward translation of the Ganos uplift indicate that the present fault geometry has existed for at least the last 2 million years.     

Correlations between soil gas and seismic activity in the Generalized Haiyuan Fault Zone,north-central China

Radon and mercury concentrations were measured in 10 fault gas profiles in Generalized Haiyuan Fault. This paper aims to predetermine the potential seismic risk in different segments of the fault zone from the perspective of geochemistry. The background value and anomaly threshold were adopted and synthesized using the maximum value method and average method to calculate concentration intensity values of radon and mercury. Fault soil gas mercury and radon concentrations show a decreasing gradient from NW to SE indicating evident segmentation. Higher values are mostly distributed in the Maomao Mountain–Tiger Mountain fault and Jingtai area. Combined with the seismotectonic background of historical and recent earthquakes and the spatial distribution characteristics of b-values, the fault soil gas concentration intensity shows a close correlation with earthquake activity within the fault zone. Concentrations of fault gas are higher and the b-value lower in areas of strong seismic activity, and regions with weak seismic activity correspond to lower fault gas concentrations and higher b-values. It is thus considered that the Jingtai area may be more dangerous than the other areas. This paper could provide vital background information for earthquake prediction in the Generalized Haiyuan Fault Zone.     

Uplift and subsidence from oblique slip: the Ganos–Marmara bend of the North Anatolian Transform, western Turkey

Bends that locally violate plate-motion-parallel geometry are common structural elements of continental transform faults. We relate the vertical component of crustal motion in the western Marmara Sea region to the NNW-pointing 18° bend on the northern branch of the North Anatolian Fault (NAF-N) between the Ganos segment, which ruptured in 1912, and the central Marmara segment, a seismic gap. Crustal shortening and uplift on the transpressive west side of the bend results in the Ganos Mountain; crustal extension and subsidence on the transtensional east side produce the Tekirdağ Basin. We propose that this vertical component of deformation is controlled by oblique slip on the non-vertical north-dipping Ganos and Tekirdağ segments of the North Anatolian Fault. We compare Holocene with Quaternary structure across the bend using new and recently published data and conclude the following. First, bend-related vertical motion is occurring primarily north of the NAF-N. This suggests that this bend is fixed to the Anatolian side of the fault. Second, current deformation is consistent with an antisymmetric pattern centered at the bend, up on the west and down on the east. Accumulated deformation is shifted to the east along the right-lateral NAF-N, however, leading to locally opposite vertical components of long- and short-term motion. Uplift has started as far west as the landward extension of the Saros trough. Current subsidence is most intense close to the bend and to the Ganos Mountain, while the basin deepens gradually from the bend eastward for 28 km along the fault. The pattern of deformation is time-transgressive if referenced to the material, but is stable if referenced to the bend. The lag between motion and structure implies a 1.1–1.4 Ma age for the basin at current dextral slip rate (2.0–2.5 cm/year). Third, the Tekirdağ is an asymmetric basin progressively tilted down toward the NAF-N, which serves as the border fault. Progressive tilt suggests that the steep northward dip of the fault decreases with depth in a listric geometry at the scale of the upper crust and is consistent with reactivation of Paleogene suture-related thrust faults. Fourth, similar thrust-fault geometry west of the bend can account for the Ganos Mountain anticline/monocline as hanging-wall-block folding and back tilting. Oblique slip on a non-vertical master fault may accommodate transtension and transpression associated with other bends along the NAF and other continental transforms.     

Tectonic elements controlling the evolution of the Gulf of Saros (northeastern Aegean Sea, Turkey)

Tectonic elements controlling the evolution of the Gulf of Saros have been studied based upon the high-resolution shallow seismic data integrated with the geological field observations. Evolution of the Gulf of Saros started in the Middle to Late Miocene due to the NW–SE compression caused by the counterclockwise movement of the Thrace and Biga peninsulas along the Thrace Fault Zone. Hence, the North Anatolian Fault Zone is not an active structural element responsible for the starting of the evolution of the Gulf of Saros. The compression caused by the rotational movement was compensated by tectonic escape along the pre-existing Ganos Fault System. Two most significant controllers of this deformation are the sinistral Ganos Fault and the dextral northern Saros Fault Zone both extending along the Gulf of Saros. The most important evidences of this movement are the left- and right-oriented shear deformations, which are correlated with structural elements, observed on the land and on the high-resolution shallow seismic records at the sea. Another important line of evidence supporting the evolution of this deformation is that the transgression started in the early-Late Miocene and turned, as a result of regional uplift, into a regression on the Gelibolu Peninsula during the Turolian and in the north of the Saros Trough during the Early Pliocene. The deformation on the Gelibolu Peninsula continued effectively until the Pleistocene. Taking into account the fact that this deformation affected the Late Pleistocene units of the Marmara Formation, the graben formation of the Gulf of Saros is interpreted as a Recent event. However, at least a small amount of compression on the Gelibolu Peninsula is observed. It is also evident that compression ceased at the northern shelf area of the Gulf of Saros.     

The measurement of soil gases and shallow temperature for determination of active faults in a geothermal area: a case study from Ömer–Gecek,Afyonkarahisar (West Anatolia)

Afyonkarahisar is a very important geothermal province of western Anatolia and has low and medium enthalpy geothermal areas. This study has been carried out for the preparation of distribution maps of soil gases (radon and carbon dioxide) and shallow soil temperature and the exploration of permeable tectonic regions associated with geothermal systems and reveal the origins of radon and carbon dioxide gases. The western district of the study area is characterized by the high radon concentration (168.30 kBq/m³), carbon dioxide ratio (0.30%), and soil temperature (21.0 °C) values. Fethibey and Demirçevre faults, which allow the circulation of geothermal fluids, have been detected in the distribution maps of radon, carbon dioxide, and shallow depth temperature and the directions of the curves in these maps correspond to the strikes of Demirçevre faults. The effect of the fault plays an important role in the change of carbon dioxide concentration along the W-E directional geological section prepared to determine the change of soil gas and shallow depth temperature values depending on lithological differences, fault existence, and geothermal reservoir depth. On the other hand, it was determined that Rn²²² concentration and soil temperature changed as a function of geothermal reservoir depth or lithological difference. Tuffs in Köprülü volcano-sedimentary units are the main source of radon due to their higher uranium contents. Besides, the carbon dioxide in Ömer–Gecek soils has geothermal origin because of the highest carbon dioxide content (99.3%) in non-condense gas. The similarities in patterns of soil temperature, radon, and carbon dioxide indicate that the variation in soil temperatures is related to radon and carbon dioxide emissions. It is concluded that soil gas and temperature measurements can be used to determine the active faults in the initial stage of geothermal exploration successfully.     

Soil-gas radon anomalies in three study areas of Central-Northern Calabria (Southern Italy)

Soil-gas radon concentrations and exhalation rates have generally been observed to be anomalously high along active faults in many parts of the world. The soil-gas method is based on the principle that faults and fractures in rocks are highly permeable pathways along which gases can migrate upward from deep crust and mantle to soil cover, retaining their source signatures. The present study summarizes the influence of fault zones on anomalous radon concentrations in soil by integrated geophysical and geo-structural analyses in three study areas of Central-Northern Calabria (Southern Italy). Soil-gas radon surveys have been carried out by means of an alpha scintillation counting system, at 12,509 locations between 2002 and 2004. A geostatistical approach has been used to estimate the spatial distribution of soil radon concentrations. Relations among soil-gas distribution and geo-structural features have been evaluated by ordinary multi-Gaussian kriging. Highest soil radon concentrations (ca. 90 kBq m^?3) have been measured in the Rossanese sector. In the three study areas, no appreciable differences can be noticed among lithotypes, with the highest concentration values (ca. 89 kBq m^?3) measured in alluvial deposit and in clay. Measurements of soil-gas radon reveal anomalies clearly connected to the tectonic structures. Increased signals are linearly distributed along regional WNW–ESE trending shear zones, with main pathways of concentration also recognizable along the E–W fault system in the Rossanese sector, the N–S fault system in the Crati Graben and the Catanzaro Trough, and the NE–SW fault system in the Catanzaro Trough. The distribution of epicentres of historical earthquakes occurred between 1184 and 2001 confirms the recent activity of the same fault systems. Soil-gas radon concentrations generally increase, as expected, with decreasing distance to the faults.     

断裂带土壤气测量方法在断层活动性研究中的应用——以嘉峪关断层为例

为了判断甘肃省嘉峪关断层监测点气氡浓度2015年6月以来的高值异常变化是否反映了嘉峪关断层活动的增强,本文基于土壤气跨断层分布规律,应用跨断层测量方法,通过多组分相关性分析及理论建模,综合分析了嘉峪关断层监测点气氡浓度高值异常变化与断层活动的关系。结果显示：监测点断层气中氡浓度快速增加期间,CO₂、CH₄和H₂的浓度没有增加,气氡与CO₂、CH₄浓度的变化不具正相关关系,表明监测点增加的氡气来源深部较浅,不代表断层活动的增强。监测点两侧跨断层测量结果表明,地表环境未改变一侧的氡气浓度符合断层气分布规律,地表环境发生改变一侧的氡气浓度不符合断层气分布规律,并且地表环境的改变时间与监测点气氡浓度异常变化时间同步。因此监测点气氡浓度的高值异常是由地表环境的改变引起的,嘉峪关断层的活动并没有增强。该方法为用断裂带土壤气体测量方法研究断层活动性的可靠性提供了思路。     

Tectonic and geologic influences on soil gas radon emission along the western extension of Damascus fault,Syria

The main purpose of this work is to demonstrate the possibility of using soil gas radon survey as a promising technique for locating the trend of western extension of Damascus fault, where it is hidden under a cover of Pliocene unconsolidated deposits. The normal level of radon background was established in a stationary area away from the tectonic influence of the fault zone. The sites of radon measurements were chosen according to the accessibility and suitability of the area, besides some indicative geologic and tectonic evidences. A total of 81 radon sampling points were analyzed, and the results revealed some reasonable spatial increases, with peak values of 2–3 times higher than the background level, trending in accordance with what is believed to be the general direction of the fault in the bedrock. However, permeability properties rather than geotectonic activities seemed to be the main causes controlling the variations of radon concentration over the concerned fault zone. Yet, the moderate level of the observed radon values could be attributed to the nature of the prevailing rock types, as well as the probable effect of locked tectonic structure due to the action of high regional compressive regime which typically originates such reverse faulting. Further, the accumulation of fill materials due to rock alteration along the plane of such dormant fault, through long geologic time, possibly led to increase in the ratio of clay minerals which may affect soil gas mobility through the medium.     

汶川地震震后大成都地区断裂带活动性氡气测量分析评价

本文运用活动断裂剖面上的土壤氡气浓度测量,对大成都地区断裂的位置、范围和活动性进行监测,监测结果表明汶川地震对大成都地区断裂带有较大的影响。通过对北川断裂虹口剖面、彭灌断裂小渔洞剖面、彭灌断裂中坝剖面、彭灌断裂白鹿剖面以及新津-蒲江断裂剖面进行监测,从测量结果分析可知:断裂剖面土壤氡浓度背景高于无断裂带地区,且受地震影响较大,距汶川地震震中越近,断裂剖面土壤氡浓度值越高;断裂剖面氡浓度异常阈值与背景值之比均不大于3,最大值与背景值之比均小于5。结合测量地点的地形、表层土壤结构等地质条件,对大成都地区震后活动断裂的相对活动性的强弱进行科学评价,认为目前大成都地区并无活动性极强的断裂,且北川断裂与新津-蒲江断裂的活动性高于彭灌断裂。     

A geostatistical approach for mapping and uncertainty assessment of geogenic radon gas in soil in an area of southern Italy

Spatial distribution of concentrations of radon gas in the soil is important for defining high risk areas because geogenic radon is the major potential source of indoor radon concentrations regardless of the construction features of buildings. An area of southern Italy (Catanzaro-Lamezia plain) was surveyed to study the relationship between radon gas concentrations in the soil, geology and structural patterns. Moreover, the uncertainty associated with the mapping of geogenic radon in soil gas was assessed. Multi-Gaussian kriging was used to map the geogenic soil gas radon concentration, while conditional sequential Gaussian simulation was used to yield a series of stochastic images representing equally probable spatial distributions of soil radon across the study area. The stochastic images generated by the sequential Gaussian simulation were used to assess the uncertainty associated with the mapping of geogenic radon in the soil and they were combined to calculate the probability of exceeding a specified critical threshold that might cause concern for human health. The study showed that emanation of radon gas radon was also dependent on geological structure and lithology. The results have provided insight into the influence of basement geochemistry on the spatial distribution of radon levels at the soil/atmosphere interface and suggested that knowledge of the geology of the area may be helpful in understanding the distribution pattern of radon near the earth’s surface.     

Seasonal variations in soil radon emanation: long-term continuous monitoring in light of seismicity

Soil gas radon release patterns have been monitored continuously for more than 3 years in the Eastern Mediterranean Province (EMP) (Southern Turkey), alongside regional seismic events, providing a multidisciplinary approach. In the period from January 2008 to January 2011, 14 earthquakes M _L ≥4 occurred in the study area. By monitoring the sites for more than 3 years, the site-characteristic patterns of soil radon emanation of each site have become evident. Radon emanation data show seasonal (semi-annual) variation characteristics; high soil radon values are between May and October and low soil radon values are between November and April. With available rainfall data, the soil gas radon data can be more reliably evaluated. It is shown in this paper that if radon emanation data are available over sufficiently long periods of time and baseline data (and their seasonal variations) are known with certainty for each monitoring site, then the observation of positive anomalies might provide a correlation or connection to seismic activity.     

Soil–gas monitoring: A tool for fault delineation studies along Hsinhua Fault (Tainan), Southern Taiwan

Many studies have shown the soil gas method to be one of the most reliable investigation tools in the research of earthquake precursory signals and fault delineation. The present research is aimed finding the relationship between soil gas distribution and tectonic systems in the vicinity of the Hsinhua Fault zone in the Tainan area of Southern Taiwan. More than 110 samples were collected along 13 traverses to find the spatial distribution of Rn, He, CO₂ and N₂. The spatial congruence of all the gases shows that N₂ is the most probable carrier gas of He, whereas CO₂ seems to be a good carrier gas of Rn in this area. From the spatial distribution of Rn, He, CO₂ and N₂ the trace of Hsinhua Fault and neotectonic features can be identified. The spatial distribution of studied gases shows a clear anomalous trend ENE–SWS along the Hsinhua Fault.     

基于SBAS InSAR的鲜水河断裂带蠕滑型滑坡特征研究

鲜水河断裂带是青藏高原东部川滇地块的一条重要边界断裂,全新世以来活动强烈,断裂带沿线岩土体结构破碎强烈,在断裂活动诱发地震、断裂蠕滑和强降雨等因素作用下,断裂带沿线滑坡、泥石流等地质灾害发育密度大,危害严重。在前人研究的基础上,采用短基线集(SBAS InSAR)的方法,基于日本对地观测卫星(ALOS 1)所获得的2007—2011年期间15景PALSAR数据,对鲜水河断裂带道孚至炉霍段的活动速率进行分析计算,获取了该段断裂带内蠕滑型滑坡5年间的时间序列形变特征。研究结果表明：鲜水河断裂带道孚至炉霍段近年来以蠕滑滑动为主,蠕滑速率为(94±078) mm/a,断裂的蠕滑作用对区域构造应力场和断裂带内滑坡具有重要的控制作用,表现为距离鲜水河断裂带越近,影像间相干性越强,稳定的相干点越多,干涉效果越好,滑坡滑动累计位移越大。沿鲜水河断裂道孚至炉霍段,共识别出98个蠕滑型滑坡,沿鲜水河断裂带两侧呈线性展布,并分析了典型蠕滑型滑坡的地表形变特征。基于SBAS InSAR的雷达数据处理方法,可以有效地分析地表的缓慢变形以及区域性蠕滑型滑坡的发育发展变化规律,研究结果对于鲜水河断裂带沿线防灾减灾及类似构造活动地区的地质灾害研究具有一定的指导作用。     

Interpretation of radon anomalies in seismotectonic and tectonic-gravitational settings: the south-eastern Crati graben (Northern Calabria, Italy)

The study area is located in the south-eastern part of the Crati valley (Northern Calabria, Italy), which is a graben bordered by N–S trending normal faults and crossed by NW–SE normal left-lateral faults. Numerous severe crustal earthquakes have affected the area in historical time. Present-day seismic activity is mainly related to the N–S faults located along the eastern border of the graben. In this area, much seismically induced deep-seated deformation has also been recognised.In the present paper, radon concentrations in soil gas have been measured and compared with (a) lithology, (b) Quaternary faults, (c) historical and instrumental seismicity, and (d) deep-seated deformation.The results highlight the following:

(a) There is no evidence of a strong correlation between lithology and the radon anomalies.

(b) A clear correlation between the N–S geometry of radon anomalies and the orientation of main fault systems has been recognised, except in the southernmost part of the area, where the radon concentrations are strongly affected by the superposition of the N–S and the NW–SE fault systems.

(c) Epicentral zones of instrumental and historical earthquakes correspond to the highest values of radon concentrations, probably indicating recent activated fault segments. In particular, high radon values occur in the zones struck by earthquakes in 1835, 1854, and 1870.

(d) Deep-seated gravitational deformation generally coincides with zones characterised by low radon concentrations.

In the studied area, the anisotropic distribution of radon concentrations is congruent with the presence of neotectonic features and deep-seated gravitational phenomena. The method used in this study could profitably contribute towards either seismic risk or deep-seated gravitational deformation analyses.     

基于物探-化探技术快速精确定位评价城市及周边隐伏断层——以广西桂林市临桂区为例

【研究目的】城市及其周边地区隐伏断层构造的探测对城市建设和经济发展具有重要影响而引起人们重点关注，根据城市的地质背景及人文条件要求，采用适宜的方法是对隐伏断层能否快速精确定位的关键，同时探测方法须具有经济快速、绿色环保及强抗干扰能力等特点。【研究方法】以广西桂林市临桂区为例，为快速精确定位被第四系覆盖的隐伏断层F1，依据该区的地质背景和地表景观特点，采用了可控源音频大地电磁测深法（CSAMT）、土壤汞气测量、氡气测量等物化探综合方法。【研究结果】经试验发现低电阻率异常与土壤汞气、氡气高值异常高度吻合，推测多方法异常重合的部位为隐伏断层的位置，而经钻探查证，揭露到了隐伏断层构造及丰富的地下水，为该区寻找与开发深部地下热水提供了依据。【结论】显然CSAMT、土壤汞气测量和氡气测量是实现桂林市及周边地区隐伏断层快速精确定位的技术组合，也为其他地区隐伏断层的探测工作提供了参考。创新点：采用地球物理、地球化学多方法在城市及周边开展隐伏断层快速探测，互相验证、最大限度减少人文干扰的影响；土壤汞气和氡气测量具有经济、快速的特点，对深部隐伏断裂构造反映明显。     

Spatial radon anomalies on active faults in California

Radon emanation has been observed to be anomalously high along active faults in many parts of the world. We tested this relationship by conducting and repeating soil-air radon surveys with a portable radon meter across several faults in California. The results confirm the existence of fault-associated radon anomalies, which show characteristic features that may be related to fault structures but vary in time due to other environmental changes, such as rainfall. Across two creeping faults in San Juan Bautista and Hollister, the radon anomalies showed prominent double peaks straddling the fault-gouge zone during dry summers, but the peak-to-background ratios diminished after significant rain fall during winter. Across a locked segment of the San Andreas fault near Olema, the anomaly has a single peak located several meters southwest of the slip zone associated with the 1906 San Francisco earthquake. Across two fault segments that ruptured during the magnitude 7.5 Landers earthquake in 1992, anomalously high radon concentration was found in the fractures three weeks after the earthquake. We attribute the fault-related anomalies to a slow vertical gas flow in or near the fault zones. Radon generated locally in subsurface soil has a concentration profile that increases three orders of magnitude from the surface to a depth of several meters; thus an upward flow that brings up deeper and radon-richer soil air to the detection level can cause a significantly higher concentration reading. This explanation is consistent with concentrations of carbon dioxide and oxygen, measured in soil-air samples collected during one of the surveys.     

缅甸拉泰-其培河段恩梅开江断裂带氡气测量

利用测量土壤中氡气异常来确定隐伏断裂的几何学特征。在缅甸拉泰—其培河段布置的四条测氡剖面中,氡气异常明显,拉泰-芒童段异常值约为本底值的3～8倍,芒童以南部分异常值比本底值高100倍,表明芒童以南地段活动性较强。氡气测量结果很好地控制了恩梅开江断裂在覆盖层之下的延伸展布方向。地表开挖及平硐揭露,很好地验证了测氡结果所推测的断层几何学特征。因此,测定土壤中氡气异常来寻找隐伏断裂的方法是可行的。     

河南卢氏盆地黄村断裂土壤氡气测量及断裂活动性分析

本文是为了确定在卢氏盆地内被第四系覆盖的黄村断裂的位置、断裂性质,分析黄村断裂与其北侧的乔家窑地热异常的关系。断裂构造是深部氡气汇集和迁移的主要通道,氡气沿断裂向上迁移,在地表浅部形成氡异常。土壤氡气异常可揭示隐伏断裂构造的位置、产状和活动性。黄村断裂通过卢氏乔家窑一带,为第四系沉积物所覆盖。沿垂直断裂走向方向布置4条测线。应用瞬时土壤测氡仪进行了野外现场测量,测试了土壤氡气浓度,确定土壤氡气异常,分析黄村断裂位置、产状和活动性。结果表明:黄村断裂带上方土壤氡气具有异常显示,异常位置与断层位置具有较好的一致性。沿QJ12测线,从南向北,土壤氡气异常形态为低-高-较高-较低-低的峰值形态。在断层带上方氡气峰值异常高于背景值的1.5倍以上,异常峰多数为2个测点以上组成。土壤氡气变化特征表明黄村断裂具有较强的活动性。利用土壤氡气异常分析了黄村断裂深部结构特征,给出了主断裂面与次级断裂面产状和位置。结合土壤氡气异常,分析了乔家地热形成机理。初步研究结果表明,豫西基底构造具有多期活动性,活化区域内的压扭性断裂,可转变为局部张性断裂,控制水热、成矿物质的迁移和富集。     

Radon as seismic precursor: new data with well water of Jalpaiguri,India

This paper reports the measurement of radon concentration in well water at the site of Jalpaiguri (26°32′N, 88°46′E) near the active fault zone of West Bengal, India. Radon concentration has been measured in well water with the help of solid-state nuclear track detectors (SSNTD). The study indicates a positive correlation between radon anomaly and earthquake. The data of radon content in well water have been compared with that in soil gas at the same site.     

Study of soil gas radon variations in the tectonically active Dharamshala and Chamba regions,Himachal Pradesh,India

Soil gas radon measurements were made in Chamba and Dharamshala regions of Himachal Pradesh, India, to study the correlation, if any, between the soil gas radon, radium activity concentration of soil, and the geology/active tectonics of the study region. Soil gas radon surveys were conducted around the local fault zones to check their tectonic activities using the soil gas technique. Soil gas radon activity concentration at thirty-five different locations in Dharamshala region has been found to be varying from 13.2 ± 1.5 to 110.8 ± 5.0 kBq m^?3 with a geometrical mean of 35.9 kBq m^?3 and geometrical standard deviation of 1.8. Radon activity concentration observed in the thirty-seven soil gas samples collected from the Chamba region of Himachal Pradesh varies from 5.2 ± 1.0 to 35.6 ± 2.5 kBq m^?3, with geometrical mean of 15.8 kBq m^?3 and geometrical standard deviation of 1.6. Average radium activity concentrations in thirty-four soil samples collected from different geological formations of Dharamshala region and Chamba region are found to be 40.4 ± 17 and 38.6 ± 1.7 Bq kg^?1, respectively. It has been observed that soil gas radon activity concentration has a wide range of variation in both Dharamshala and Chamba regions, while radium activity concentrations in soil samples are more or less same in both the regions. Moreover, soil gas radon activity concentration has a better positive correlation with the radium activity concentration in soil samples collected from Chamba region as compared to Dharamshala region.