Mathilde B. Sørensen

Exercise and diet interventions improve perceptions of self in middle‐aged adults

The effect of a 1‐year exercise and diet intervention program on global self‐concept, perceptions of the body, physical competence, exercise mastery, social competence, social comfort, and fitness was examined with 208 healthy individuals (191 males, 17 females) aged 39–49 years (mean age 44.9) with elevated risk factors for cardiovascular disease. The relative utility of the skill development versus the self‐enhancement model of the self‐concept/behaviour relationship was tested. The participants were randomized into four groups: diet (n=53), diet and exercise (n=64), exercise (n=48) and no active intervention (n=43). Measurements were made by the Harter adult self perception profile (HASPP) and the self‐perception in exercise questionnaire (SPEQ). Two‐way ANOVA analyses revealed that exercise participation, with or without diet, enhanced self‐perceptions of physical mastery and ability, body perception, fitness and social comfort. The unique contribution of diet indicated enhanced body perception. No effect was found of diet or exercise on global self‐concept. Exercise participation had a positive effect on perceptions of the self, and the higher the compliance with the exercise program, the stronger were the effects on the self‐perceptions. This supported the skill development model of the self‐concept/behaviour relationship. As the pretest self‐concept scores did not predict exercise compliance, the self‐enhancement model of the self‐concept/behaviour relationship was not supported.

Sensitivity of Ground-Motion Simulations to Earthquake Source Parameters: A Case Study for Istanbul, Turkey

Following the disastrous earthquakes in Izmit and Duzce along the North Anatolian fault in 1999, the earthquake hazard in the Istanbul area became a great concern. In this study we simulate strong ground motions caused by a scenario earthquake (M 7.5) in the Marmara Sea, and investigate the effect of varying the input parameters on the broadband frequency ground motion. Simulations are based on a multiasperity source model that involves the combined rupture of the North Anatolian fault segments beneath the Marmara Sea. We use a hybrid model combin- ing a deterministic simulation of the low frequencies (0.1-1.0 Hz) with a semisto- chastic simulation of the high frequencies (1.0-10.0 Hz). Computation at each fre- quency range is performed separately and the total ground motion is combined in the time domain. Computations are linear and are performed at bedrock level, thereby not taking any effect of local geological conditions into account. We calculate a total of 17 earthquake scenarios corresponding to different source and attenuation param- eters to study their effect on the ground motion. The most significant parameters in terms of ground-shaking level are the rise time, rupture velocity, rupture initiation point, and stress drop. The largest variability of strong ground motions is observed in regions adjacent to asperities and is associated with frequencies higher than 5 Hz. For lower frequencies our simulated velocity spectra within the Istanbul area are fairly stable among scenarios. The average standard deviations of all ground-motion measures are less than 35% of the mean. Online material: Figures of peak ground acceleration and peak ground velocity and their differences to the reference scenario values.

Simulated Strong Ground Motions for the Great M 9.3 Sumatra-Andaman Earthquake of 26 December 2004

On 26 December 2004, a devastating earthquake of M 9.3 occurred offshore northern Sumatra. Due to the size of this earthquake and the accompanying tsunami wave, disastrous consequences have been observed in several countries around the Indian Ocean. The tectonics in the region are characterized by the oblique, north-northeast-oriented subduction of the Indian-Australian plate under the Sunda microplate with a rate of 6-6.5 cm/yr. This oblique convergence results in strain partitioning, where the trench-perpendicular thrust faulting along the subducting slab accommodates the east-west component of the motion, whereas the north-south component of the motion is probably accommodated by the right-lateral strike-slip faulting along the Great Sumatran fault and the Mentawi fault. Source parameters of the 26 December 2004 event have been used for modeling the resulting ground motions in the nearby affected regions. Results give an insight on the importance of ground shaking in the total destruction of places like Banda Aceh, northern Sumatra, Indonesia. The modeling is performed for a multiasperity finite fault using a hybrid procedure combining deterministic modeling at low frequencies and semistochastic modeling at high frequencies. Results show that strong shaking was distributed over a large area including northwestern Sumatra and its offshore islands. In Banda Aceh, which experienced significant damage, bedrock velocities reached 60 cm/sec with duration of the shaking of ca. 150 sec. The largest ground motions occurred near the strongest asperities of the fault plane, where velocities of 200 cm/sec are modeled for bedrock conditions.

Attenuation of Macroseismic Intensity: A New Relation for the Marmara Sea Region, Northwest Turkey

Prediction equations for macroseismic intensity are the backbone of seismic hazard assessment, of source parameter estimation, and of shake map generation in cases where an output in terms of intensity is desired. This is especially required when a direct relation to the damage associated with ground shaking is of interest or if ground shaking estimates will be used for informing nonseismologists such as emergency response teams or the general public. In the current study we derive ground-motion prediction equations for macroseismic intensity valid for the Marmara Sea region, northwest Turkey. The relations have a physical basis and are easy to implement for the user. In one relation, the finite extent of the fault rupture is accounted for by defining distance as the Joyner–Boore distance leading to the relation ![Graphic][1] where M w is the moment magnitude, R JB is the Joyner–Boore distance, and h is the hypocentral depth. Furthermore, a relation based on the epicentral distance ( R epi) is derived for application in cases where the extent of the fault plane is unknown: ![Graphic][2] The relations are valid for the ranges 5≤ I ≤10, 5.9≤ M w≤7.4, and R ≤350 km. It is shown that inclusion of the rupture dimensions leads to an improvement in the ability of the relation to fit observations in the near field for large earthquakes. Comparison to already existing intensity prediction equations for the region shows that the new relations provide better estimates of the macroseismic intensity distribution, especially in the region near the rupturing fault plane. [1]: /embed/inline-graphic-1.gif [2]: /embed/inline-graphic-2.gif

Continued Earthquake Hazard in Northern Sumatra

The occurrence of two large earthquakes (Mw = 8.4 and Mw = 7.9) along the Sumatran west coast on 12 September 2007 as well as an Mw = 7.4 event on 20 February 2008 have again put the high earthquake hazard of this region into focus. These events are the most recent in a series of major subduction zone earthquakes that began with the great Mw = 9.3 event of 26 December 2004 followed by an Mw = 8.7 event on 28 March 2005 [Bilham, 2005; Lay et al., 2005; Stein and Okal, 2005]. The major subduction zone earthquakes have been propagating southward along the Sunda trench, and the remaining stress is expected to be released along the subduction zone in a long stretch from the Andaman Sea in the north to the southernmost extension of the recent ruptures, especially in the southernmost part close to the Sunda Strait (Figure 1). Also, there is an additional and significant hazard due to potential earthquakes along the Great Sumatran Fault (GSF), a major rightlateral strike-slip fault parallel to the western coast of Sumatra. The GSF accommodates the component of plate convergence parallel to the trench, where strain partitioning is a result of the oblique collision along the Sunda trench.

Intensity attenuation in the Campania region, Southern Italy

Ground motion prediction equations (GMPE) in terms of macroseismic intensity are a prerequisite for intensity-based shake maps and seismic hazard assessment and have the advantage of direct relation to earthquake damage and good data availability also for historical events. In this study, we derive GMPE for macroseismic intensity for the Campania region in southern Italy. This region is highly exposed to the seismic hazard related to the high seismicity with moderate- to large-magnitude earthquakes in the Appenninic belt. The relations are based on physical considerations and are easy to implement for the user. The uncertainties in earthquake source parameters are accounted for through a Monte Carlo approach and results are compared to those obtained through a standard regression scheme. One relation takes into account the finite dimensions of the fault plane and describes the site intensity as a function of Joyner–Boore distance. Additionally, a relation describing the intensity as a function of epicentral distance is derived for implementation in cases where the dimensions of the fault plane are unknown. The relations are based on an extensive dataset of macroseismic intensities for large earthquakes in the Campania region and are valid in the magnitude range Mw = 6.3–7.0 for shallow crustal earthquakes. Results indicate that the uncertainties in earthquake source parameters are negligible in comparison to the spread in the intensity data. The GMPE provide a good overall fit to historical earthquakes in the region and can provide the intensities for a future earthquake within 1 intensity unit.

Incorporating Simulated Ground Motion in Seismic Risk Assessment: Application to the Lower Indian Himalayas

In this study, the effects of implementing stochastic finite fault ground motion simulations in earthquake hazard and risk assessment are evaluated. The investigations are conducted for the city of Dehradun (Indian Himalayas). We compare two ground motion estimation techniques: a ground motion prediction equation–based technique and a simulation-based technique. The comparison focuses on the differences the techniques imply on earthquake damage and loss estimates. Ground motion simulations are first calibrated against the instrumental recordings of the 1991 Mw 6.8 Uttarkashi earthquake. Afterward, a number of events are considered with different magnitude, distance, and azimuth to the source. Results indicate large differences between ground motion and loss estimates derived by the two methods, especially in the direction of rupture propagation, which persist to 2–2.5 fault lengths distance. It is therefore strongly recommended to consider rupture kinematics and orientation to the test bed when providing ground motion estimates for near-field earthquake loss assessment studies.

Tectonic Processes in the Jan Mayen Fracture Zone Based on Earthquake Occurrence and Bathymetry

Jan Mayen is an active volcanic island situated along the mid-Atlantic Ridge north of Iceland. It is closely connected with the geodynamic processes associated with the interaction between the Jan Mayen Fracture Zone (jmfz) and the slowly spreading Kolbeinsey and Mohns Ridges. Despite the significant tectonic activity expressed by the frequent occurrence of medium to large earthquakes, detailed correlation between individual events and the causative faults along the jmfz has been lacking. Recently acquired detailed bathymetric data in the vicinity of Jan Mayen has allowed us to document such correlation for the first time. The earthquake of 14 April 2004 ( M w 6), which occurred along the jmfz, was studied in detail and correlated with the bathymetry. Locations of aftershocks within the first 12 hours after the mainshock outline a 10-km-long fault plane. Interactions between various fault systems are demonstrated through locations of later aftershocks, which indicate that supposedly normal fault structures to the north of the ruptured fault, in the Jan Mayen Platform, have been reactivated. Correlation of the waveforms shows that events located on these structures are significantly different from activity at neighboring structures. Coulomb stress modeling gives an explanation to the locations of the aftershocks but cannot reveal any information about their mechanisms.

Probabilistic Tsunami Hazard Analysis: Multiple Sources and Global Applications

Applying probabilistic methods to infrequent but devastating natural events is intrinsically challenging. For tsunami analyses, a suite of geophysical assessments should be in principle evaluated because of the different causes generating tsunamis (earthquakes, landslides, volcanic activity, meteorological events, and asteroid impacts) with varying mean recurrence rates. Probabilistic Tsunami Hazard Analyses (PTHAs) are conducted in different areas of the world at global, regional, and local scales with the aim of understanding tsunami hazard to inform tsunami risk reduction activities. PTHAs enhance knowledge of the potential tsunamigenic threat by estimating the probability of exceeding specific levels of tsunami intensity metrics (e.g., run-up or maximum inundation heights) within a certain period of time (exposure time) at given locations (target sites); these estimates can be summarized in hazard maps or hazard curves. This discussion presents a broad overview of PTHA, including (i) sources and mechanisms of tsunami generation, emphasizing the variety and complexity of the tsunami sources and their generation mechanisms, (ii) developments in modeling the propagation and impact of tsunami waves, and (iii) statistical procedures for tsunami hazard estimates that include the associated epistemic and aleatoric uncertainties. Key elements in understanding the potential tsunami hazard are discussed, in light of the rapid development of PTHA methods during the last decade and the globally distributed applications, including the importance of considering multiple sources, their relative intensities, probabilities of occurrence, and uncertainties in an integrated and consistent probabilistic framework.