Earthquake

An earthquake is a phenomenon that results from and is powered by the sudden release of stored energy that radiates seismic waves. At the Earth's surface, earthquakes may manifest themselves by a shaking or displacement of the ground and sometimes tsunamis, which may lead to loss of life and destruction of property.

Earthquakes may occur naturally or as a result of human activities. In its most generic sense, the word earthquake is used to describe any seismic event—whether a natural phenomenon or an event caused by humans—that generates seismic waves.

Most naturally occurring earthquakes are related to the tectonic nature of the Earth. Such earthquakes are called tectonic earthquakes. The Earth's lithosphere is a patch work of plates (see plate tectonics) in slow but constant motion caused by the heat in the Earth's mantle and core. Plate boundaries glide past each other, creating frictional stress. When the frictional stress exceeds a critical value, called local strength, a sudden failure occurs. The boundary of tectonic plates along which failure occurs is called the fault plane. When the failure at the fault plane results in a violent displacement of the Earth's crust, the elastic strain energy is released and elastic waves are radiated, thus causing an earthquake. It is estimated that only 10 percent or less of an earthquake's total energy is ultimately radiated as seismic energy, while most of the earthquake's energy is used to power the earthquake fracture growth and is eventually converted into heat. Therefore, earthquakes lower the Earth's available potential energy and thermal energy, though these losses are negligible. To describe the physical process of occurrence of an earthquake, seismologists use the Elastic-rebound theory.

The majority of tectonic earthquakes originate at depths not exceeding a few tens of kilometers. Earthquakes occurring at boundaries of tectonic plates are called interplate earthquakes, while the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes.

Health maintenance

A Health Maintenance Organization is a type of Managed Care Organization that provides a form of health insurance coverage in the United States that is fulfilled through hospitals, doctors, and other providers with which the HMO has a contract. Unlike traditional indemnity insurance, care provided in an HMO generally follows a set of care guidelines provided through the HMO's network of providers. Under this model, providers contract with an HMO to receive more patients and in return usually agree to provide services at a discount. This arrangement allows the HMO to charge a lower monthly premium, which is an advantage over indemnity insurance, provided that its members are willing to abide by the additional restrictions.

In addition to using their contracts with providers for services at a lower price, HMOs hope to gain an advantage over traditional insurance plans by managing their patients' health care and reducing unnecessary services. To achieve this, most HMOs require members to select a primary care physician (PCP), a doctor who acts as a "gatekeeper" to medical services. PCPs are usually internists, pediatricians, family doctors, or general practitioners

Electronic Bass Designs

Musicians have embraced a wide variety of different electric bass designs, which include a huge variety of options for the body, neck, pickups, and other features. Musicians have become open minded towards the new technologies and approaches to musical instrument design that have developed for the electric bass. As well, instruments handmade by highly-skilled masters of the craft of lutherie (guitar-making) are becoming an increasingly popular choice for professional and highly-skilled amateur bassists. These developments have given the modern bass player a wide range of options when choosing an instrument. Design options include

Bodies are typically made of wood although other materials such as graphite (for example, some of the Steinberger designs) have also been used. A wide variety of woods are suitable - the most common include alder, mahogany and ash, and bubinga. The choice of body material and shape can have a significant impact on the timbre of the completed instrument as well as on aesthetic considerations