Bandar Lampung is the capital of Lampung Province which is crossed by faults, one of the faults that crosses Bandar Lampung namely the Panjang Fault or commonly called the Tarahan Fault, it is making the Bandar Lampung to be a potential earthquake area. Over the past 20 years many large earthquakes have rocked Indonesia, especially in the western part of Indonesia, such as Aceh, Nias, Padang, Bengkulu, Tasikmalaya, and Ciamis. Lampung Province is located near the subduction boundary of the Indo-Australian Plate against the Eurasian Plate, and also there is another fault, the Semangko Fault. Therefore, Lampung Province and especially Bandar Lampung have greater potential to the earthquake effect. The potential of this earthquake needs to be carried out by disaster mitigation activities to minimize the consequences that occur due to earthquakes, namely by classifying soil vulnerability by characterizing site effects. This study aims to determine the site effect based on dominant frequency parameters. The study was used 135 microtremor measurement points by using the Ref-Tek 130-SMHR strong motion accelerograph type (3 components). Microtremor data was analyzed using the Horizontal to Vertical Spectral Ratio (HVSR) method in Geopsy software. Based on the HVSR method, the Bandar Lampung City is dominated by soft soil types with a dominant frequency of f0 <1.33 Hz. It’s shows that Bandar Lampung City has a high vulnerability to earthquakes. Moreover, based on map analysis of the dominant frequency, the areas that have the highest risk are Kecamatan Panjang, Bumiwaras, Telukbetung Utara, Teluk Betung Selatan, Telukbetung Timur, Tanjungkarang Pusat, Tanjungkarang Barat, Rajabasa, Enggal, Langkapura, Kedamaian, Wayhalim, and Kedaton.

<pre><strong><em>Abstract. </em></strong><em>Lake Sentani is located in Jayapura Regency, Papua Province with an area 9,360 ha and 70-90 meters above sea level. The lake directly adjacent to Cycloops Mountains Nature Reserve, obtaining supplies of about 34 springs.  The aim of the research was to describes the lake bathymetry as a basic information for the utilization. The function are as habitat place for many species, water resources, fisheries, transport and tourism. M</em><em>orphometry and bathymetry of the lake is very important for the sustainable management of the lake functions as a topography and relief lakes that have different extreme depths. Making the bathymetry of the lake is done with the acoustic method. Recording data using Garmin GPSmap 76CSx and Garmin Echo 100 Fishfinder. The result of the research showed that the depth of Lake Sentani with 9 variation at the different location, in generally range 15-23 m. Meanwhile, the waters of the deepest lake located in the eastern part of the lake is more than 70 m and the lowest depths of 0-7 m are in the middle of the Sentani area.</em></pre><p><strong><em>Keywords:</em></strong><em> bathymetry; morphometry; acoustic method; Garmin Echo 100 Fishfinder; Lake Sentani</em></p><p><strong>Abstrak. </strong>Danau Sentani terletak di Kabupaten Jayapura, Provinsi Papua dengan luas 9.360 ha dan ketinggian   70–90 m dpl. Danau ini berbatasan langsung dengan Cagar Alam Pegunungan Cycloops dan memperoleh suplai dari sekitar 34 sumber mata air. Tujuan penelitian ini adalah menggambarkan batimetri danau sebagai informasi dasar pemanfaatan danau. Fungsi danau adalah sebagai habitat makhluk hidup, sumber air masyarakat sekitar, perikanan, transportasi dan pariwisata. Mengetahui morfometri dan batimetri danau sangat penting untuk pengelolaan fungsi danau yang berkelanjutan karena kondisi topografi dan relief danau yang memiliki perbedaan kedalaman ekstrim. Pembuatan batimetri danau dilakukan dengan metode akustik. Perekaman data menggunakan <em>Garmin GPSmap 76CSx</em> dan <em>Garmin Echo 100 Fishfinder</em>. Hasil penelitian menunjukkan bahwa kedalaman perairan Danau Sentani terdiri dari 9 variasi yang umumnya berkisar 15–23 m. Perairan danau terdalam berada di wilayah timur danau yaitu lebih dari 70 m dan kedalaman terendah antara 0–7 m berada di wilayah Sentani tengah.</p><p><strong>Kata kunci:</strong><em> batimetri; morfometri; metode akustik; Garmin Echo 100 Fishfinder; Danau Sentani</em><em></em></p>

Overexploitation in 1980-2000 caused a lot of groundwater loss in the aquifer coastal of Bandar Lampung. Groundwater has been degraded with increasing salinity due to the intrusion of seawater. In 2013, the intrusion extended 400 m from the coastline. Subsurface geological mapping is carried out to examine alluvial formation’s material constituents and the ability to transfer seawater to land. Three well explorations combined with three geoelectric tomography and 51 points of gravity. The gravity method is used to map structures that can connect coastal aquifers and land aquifers. Meanwhile, geoelectric tomography to map the presence of aquifers and low resistivity zones by seawater intrusion. The coastline has relatively shallow aquifers at a depth of 2-10 m in a sand layer with coral inserts, while the lower part is composed of silt and clay. The aquifer has experienced a decrease in resistivity of fewer than 10 ohms.m appears in the three circular patterns, caused by seawater. In addition to the permeable zone of shallow aquifers, there is a northwest-southeast trending structure that can channel seawater to land aquifers.

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